Annals of the Royal College of Surgeons of England (1975) vol 56
Movements at the hip joint J Joseph
MD DSC FRCOG
Department of Anatomy, Guy's Hospital Medical School, London
Summary Movements at the hip joint are first discussed in terms of free movement of the lower limb on the trunk. The biomechanics of standing on one lower limb limited to the situation
in the coronal plane are presented. The role of the hip muscles in the upright posture and
AN i
in the movements at the hip joint during walking on the flat and upstairs and downstairs is described.
Introduction Although it nay be old-fashioned to use the well-known terms flexion, extension, etc., to describe the movements at a joint, I propose to use them with reference to the movements at the hip because they are well known, easily understood, and in actual fact difficult to replace. I will, however, confine myself to such aspects of movements as are controversial or not well known. In the case of the hip joint, in addition to movements of the lower linmb on the trunk, movements of the trunk on the lower limb have to be considered. It is also necessarv to appreciate the way in which forces act on the hip joint during varioUs activities, but I will limit my remarks on the last-mentioned subject mainly to one particular situation-namely, standing on one lower limb. Movements of lower limb on trunk Flexion at the hip joint is Flexion usually described as being limited, if the leg Arnott Dernonistation given on 24th April 1974
JOSEPHS
N
-
FIG.
named
(A) Arbuthnot Lane, Bexley, Kent, after Sir W Arbuthnot Lane (1856-
surgeon of Guy's Hospital. (B) Joseph's Lane, near Penzance, Cornwall. (This street has no connection with the autthor but it is the best he can do.)
I943), famous
Movements at the hip joint is bent at the knee, by contact of the thigh with the anterior abdominal wall',2. At least 2o0 years ago I suggested that this is quite misleading and that flexion at the hip is limited to about I00° with the leg bent at the knee and that contact between the thigh and the abdominal wall is possible only with the trunk flexed and some additional passive movement at the hip produced by clasping one s arms round the leg and thigh. This observaticn of mine was not original in that W Arbuthnot Lane3 in I896 said, 'On picking up that very excellent text-book Gray's Anatomy I find the following stated deliberately and without reservation of any sort"Flexion of the hip joint is arrested by the soft parts of the thigh and abdominal wall being brought into contact." Now gentlemen, this statement is, except possibly in the case of obese people absolutely without any foundation; in other words, it is uttterly false, as you will see by examining a dissected speciment.' (En passant, there cannot be many Fellows of this College who have a street
I93
named after them. Arbuthnot Lane is in Bexley off the M2 and Lane lived in a house there (Fig. i).) In all fairness I should add that on p. 449 of the same edition of Gray's Anatomy there appears the emendation made by Professor T B Johnston4 as a result of his seeing Lane's article and my confirmation of what Lane said-'Contact of the front of the thigh with the abdominal wall implies supplementary movements at the sacro-iliac [sic], lumbosacral and other intervertebral joints, for it is not usually possible to obtain more than I00° of forward angulation at the joint itself.' Fig. 2 illustrates flexion at the hip in a ballet dancer. I would like to emphasize two points. In B, C, and D it can be seen that her maximum flexion at the hip, whether with the leg straight or bent at the knee or with the lower limb pulled up by the hand, involves some flattening of the lumbar concavity that is, flexion of the trunk. Secondly, in D the additional flexion is associated with some abduction at the hip. It should be pointed out that the main flex-
_C_ FIG. 2 (A) Lateral view of ballet dancer. (B) Flexion of thigh at hip with leg extended at knee. (C) Flexion of thigh at hip with leg flexed at knee. (D) Flexion-abduction of thigh at hip with added passive movement. Note the flattening of the lumbar curvature in B, C, and D.
194
J joseph
of the thigh at the hip are the iliacus and muscles and that all the other muscles described as flexors (rectus femoris, tensor fasciae latae, sartorius, pectineus, some of the adductors) cannot fully and effectively replace paralysed or cut iliacus and psoas muscles. ors
psoas
Extension Extension at the hip from the anatomical position is a very limited movement and even the ballet dancer (Fig. 3) shows very limited extension. It should be noted that in A the lumbar curvature is increased and that the subject is leaning forwards. In B the position of the right lower limb, an attractive arabesque, is almost entirely due to extension of the trunk. The gluteus maximus muscle is always regarded as the main extensor of the thigh at the hip, but if a movement is performed slowly and with limited force it is the hamstrings which are active and the gluteus maximus is recruited for rapid or forceful movement'7. This is shown in the electromyographic record in Fig. 4. The importance of the gluteus maximus in extension of the trunk on the lower limb must be mentioned but will be dealt with more fully when I discuss posture and walking. Abduction Abduction of the lower limb at the hip joint is defined as movement of the limb in the coronal plane away from the body. The main muscles involved are the gluteus medius and gluteus minimus and I would like to emphasize the secondary role of the other muscles (gluteus maximus, tensor fasciae latae, and the short posterior muscles which are mainly lateral rotators). Milch8'9 gives an average figure of 450 for this movement and in Fig. 5B it can be seen that it is rather surprisingly limited in a ballet dancer. However, if she flexes the leg at the knee while at the same time abducting and to some extent flexing the thigh (Fig. 5C) she can then extend the leg and produce the
FVIG. (B)
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3
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FIG. 4 Electromyographic recording from hamstrings and gluteus maximus. (A) During slow extension of lower limb at hip. Note that gluteus maximus becomes active towards the end of the movement. (B) Sudden rapid extension of lower limb at hip. Note simultaneous onset of activity in both muscles. Reproduced by permission from New Developments in Electromyography and Clinical Neurophysiology, vol. i-.
Movements at the hip joint position seen in Fig. 5D. This is called de'velope a la seconde and the develope part-that is, the flexing of the leg appears to be an important part in achieving the go9 of abduction seen in Fig. 5C. It should be added that this position of the limnb involves lateral flexion of the trunk. When discussing abduction of the thigh at the hip and the action of the gluteus medius muscle it is more important to refer to the role of this muscle in preventing the opposite, unsupported side from falling when an individual stands on one lower limb. This is seen in every step in walking and going up and down steps. I would like to say something about the forces acting at the hip joint when a subject is standing on one limb. Modem work in this subject is associated with Elftman'0'l' and Inman and his co-workers in the Biomechanics Laboratory in San Francisco12. Inman calculated that when standing on one lower limb the pressure on the head of the femur was about 2.4-2.6 X body weight. This is the resultant of two forces-the body weight and the pull of the abductor muscles,
A
B
C
195
as is shown in Fig. 6. This is also dealt with very fully by Strange in his excellent book on the hip"3. In Fig. 6 the weight of the body minus one lower limb is W and the centre of gravity of this mass is G. The centre of the head of the femur is 0 and the body weight produces a turning movement about O and equals W X OA. The angle APO (200) can be determined. The line of pull by the abductors (PF) can be obtained from the study of X-ray films and cadavers and the ratio of OB:OA is found to be I:2.5. The force exerted by the abductors is therefore .5 X W at an angle of 80. The resultant force PR can now be calculated and is approximately 3.43 X W acting at 200. Certain comments can be made regarding these calculations. Firstly, it is assumed that the head of the femur is a perfect sphere and that 0 can be accurately determined. Seconndly, the shift of the centre of gravity over the supporting limb is very variable. If it is moved directly over the head of the feimur the force exerted by the abductor muscles is reduced to zero. This is unlikely, btut the shorter OA becomes the less force
D
FIG. 5 (A) Posterior view of ballet dancer. (B) Abduction of thigh at hip and (C) flexion of leg at knee as precursor to (D) abduction-flexion of lower limb at hip. Note in D lateral flexion of trunk.
I96
1 Joseph
Body weight minus one lower limb F = Force produced by abductors R = Resultant force on femoral head
W
R FIG. 6 Forces acting on head of femur in coronal plane while subject stands on one lower limb.
is required to be exerted by the abductors, and consequently the less force is applied to the head of the femur.
Adduction The movement of adduction is limited to about I5° according to Milch9, and it is difficult to understand why there is such a relatively large mass of adductor muscles. Nobody seems to be very happy about the explanation that they are used in horse-riding or tree-climbing, and a little thought on their importance in sexual intercourse raises more questions than answers.
Rotation From the anatomical position the extent to which the thigh can be rotated laterally and medially at the hip varies a great deal between individuals, but there is general agreement that these movements are increased considerably if the thigh is flexed. Milch9 gives figures of 6o0 for lateral rotation and 400 for medial rotation with the thigh flexed at the hip. This increase in rotation should be kept in mind because in a clinical examination, with the patient supine on the bed or couch, rotation is estimated with the thigh and leg flexed. Usually the heel is held in one hand and the knee is pushed laterally and medially to estimate the amount of lateral and medial rotation respectively. This also means that the axis of rotation is through the head of the femur and the heel. In the anatomical position the axis is said to be through the head and intercondylar notch of the femur (or lateral or medial condyle, depending on which book one is reading) and the amount of movement is very much less. It is interesting to note that position one in classical ballet involves standing with the feet turned out so that they form a straight linethat is, each lower limb is laterally rotated through 9o0. This is difficult to achieve and is assisted if the dancer first flexes the thighs and legs at the hips and knees, laterally rotates the lower limb as much as possible, usuially to 9o0, and then straightens the thigh and leg. The additional rotation associated with the flexed thigh and the added lateral rotation of the leg at the knee allows rotation of the foot through go9. Anyone attempting this will notice that the inner border of the foot is pressed hard on the ground, so that the lower limb is prevented from turning inwards. There is general agreement that the important lateral rotators are the small muscles on the back of the hip joint (piriformis, obturator internus, and quadratus femoris) as well as
Movements at the hip joint the obturator externus. I was very pleased to be told, although I cannot find the reference, that the main medial rotators are the gluteus minimus and the anterior part of the gluteus medius, and these muscles are assisted bv the tensor fasciae latae. This raises the vexed problem of the action of the iliopsoas muscle. Keagy et al."4 investigated the psoas major muscle by means of intramuscular electrodes through the back and found that it was neither a lateral nor a medial rotator. Tdnnis"', using intramuscular electrodes in the groin, made the same observation, as did Basmajian'6, who put needles into the iliacus muscle. It appears then that the iliopsoas is only a flexor of the thigh in spite of MeKibbin'7 and Fitzgerald'8, who maintain that it is also a lateral rotator. Both Cunningham' and Gray' in their most recent editions do not associate the iliopsoas muscle with rotation except for a passing reference by the latter to the lateral rotation of the femur in fractures of its neck.
Role of muscles of the hip joint while standing at ease This has been extensively investigated (see Josephl9 for list of references). The posture is one in which the weight is on both limbs with the feet about 25 cm apart and pointing comfortably omtwards, and the upper limbs are alongside the trunk or behind the back with the hands lightly clasped. There appears to be general agreement that none of the hip muscles are contracted and this is due to the line of weight of the body above the hip joints falling behind the transverse axis of these joints and the support given by their powerful anterior ligaments. Movements forwards of the centre of gravity of the trunk by swaying forwards or raising the upper limb forwards restults in contraction of the hamstrings, which prevents flexion of the trunk at the hip joints6.
197
Movements at the hip while walking The movements which take place at the hip joints while walking are complex, but they are capable of a degree of analysis. When walking is discussed it is important to accept an agreed description of a step (Fig. 7). A step may be said to begin when the heel strikes the ground (heel strike). This is followed by a stance phase during which the weight is transferred from the heel along the sole to the heads of the metatarsals and then to the plantar surface of the great toe. The lower limb is lifted from the ground (toe off) and enters the swing phase which ends with the heel strike. The stance phase occupies about 3/5ths of the whole step and the swing phase 2/sths. At the beginning and end of the stance phase the opposite limb is on the ground (double stance phases). Each of these occupies about I /5th of the whole step. The most obvious movement at the hip is extension during the stance phase and flexion during the swing phase. It is interesting that both gluteus maximus and the hamstrings contract during only the first half of the stance phase-that is, until the trunk is vertically over the hip joint-and stop contracting during the second half of this phase20. With the foot on the ground the forward momentum of the body produces sufficient force to continue the extension at the hip. The contraction of the gluteus maximus and hamstrings may pull the trunk over the supporting limb in the early stance phase or prevent the trunk flexing at the hip, as suggested by Strange'3. In a somewhat similar way the iliopsoas contracts during only the first part of flexion at the hip in the swing phase20. I would like to quote Keagy et al.'4 on this-'While walking forward, activity regularly appeared 8o to I20 ms before toe off, and persisted only during the initial 40%/0 of the swing phase. This indicates and confirms that the prime
I98
J Joseph
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FIG. 7 Periods of activity of some hip muscles of right lower limb in I4 subjects (8 male, 6 female) while walking on the flat. One complete step divided into 23 stages. Interrupted lines and numbers in parentheses indicate activity in a proportion of suibjects.
function of this muscle in gait is to initiate and accelerate the forward advancement of the limb. Once motion is started, the muscle rests'. There is no evidence that during the second half of the stance phase the flexors of the hip are active to carry the trunk along with the hip and rotate the pelvis forwards at the hip of the supporting limb, as suggested by Straqrge`. There is no need for me to dilate on the role of the abductors (gluteus medius and minimus and tensor fasciae latae) during the stance phase. Their contraction prevents the falling of the body to the unsupported side. The role of the adductors in walking has been investigated by only one group of workers, whose pioneer studies in the electromyography of muscles used in gait cannot go unmentioned21. They found marked activity of the adductors at the end of the stance phase and also a smaller peak of activity at the beginning of the same phase. They related these periods
of activity to the stabilizing of the pelvis on the femora during the period of double support and controlling horizontal rotation of the pelvis. Activity of the adductors, however, is seen at the beginning and end of the swing phase and it is suggested that the adductors control the frontal plane movements of the lower limb during this phase. It is usually assumed that lateral rotation of the lower limb takes place during the swing phase. This could be due to contraction of the small muscles at the back of the hip joint, but these have not been investigated. The San Francisco workers think that this rotation may be due to the adductors. In many individuals as the heel rises and the weight is on the anterior part of the the sole the heel is seen to move inwards-that is, a lateral rotation takes place. The adductors or the gluteus maximus may produce this. Of more importance is the medial rotation of the pelvis on the lower limb during the
Movements at the hip joint
flexed at the hip and the knee and the body is lifted upwards by straightening the limb. The extension at the hip is due to marked contraction of the hamstrings and gluteus maximus and this activity continues until the opposite limb is placed on the next step. There is a phase of single limb support while the limb is being straightened and, as expected, this is accompanied by contraction of the gluteus medius. The iliopsoas is contracted during the whole of the swing phase-that is, when the limb is being flexed at the hip and knee and lifted on to the step above. On going downstairs the lowering of the body to the next step is achieved by the controlled lengthening of the soleus and quadriceps femoris. There is only a very short contraction of the gluteus maximus at the beginning of the stance phase, and the hamstrings are briefly contracted to flex the leg at the knee in the middle of the swing phase.
stance phase. This increases the length of the step and is essential because of the limited extension possible at the hip joint. The muscles which cause medial rotation (the gluteus minimus, tensor fasciae latae, and anterior part of the gluteus medius) are contracted during this phase to prevent the body falling to the unsupported side. This medial rotation is said to be more marked in the female sex. It has been shown by Chapman and Kurokana22 that there is a 'quantitative similarity between the average pelvic and shoulder rotations in the two sexes. Observations of men's and women's gait patterns led Us to expect a greater amplitude of individual transverse rotations in women. On the contrary, most of the greatest individual rotations measured occurred in men.' Joseph and Watson (Figs. 8 and 9) have shown that when going upstairs the lower limb which is placed on the step above is
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FRAME NUMBER FIG. 8 Periods of activity of some hip muscles of right lower limb in 6 male subjects while walking upstairs. One complete step divided into 20 stages. Reproduced by permission from the Journal of Bone and Joint Surgerv23.
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FRAME NUMBER FIG. 9 Periods of activity of some hip muscles of right lower limb in 6 male subjects while walking downstairs. One complete step divided into ig stages. Reproduced by permission from the Journal of Bone and Joint Surgery"3.
The gluteus medius, as expected, is con- with the complicated calculations involved in tracted during the single stance phase. It is estimating the forces acting on the hip joint, interesting to note that the trunk is kept al- but one is struck by the differences in the remost vertically above the thigh during the sults obtained by various investigators who stance phase so that there is minimal or no state that the force acting on the head of contraction of the flexors and extensors at the the femur while standing on one limb ranges hip. All these observations in relation to going from 2.4 to 6.o X body weight and while upstairs and downstairs confirmed those made walking from 2.5 to 6.o X body weight. That in a somwehat inaccessible report published a correct estimation of the forces involved is of paramount importance is obvious to anyin 195324. one interested in the hip joint and especially its replacement, but I am now told that the Conclusion One cannot end this lecture on movements strength of the prosthesis is only one part of at the hip joint without a reference to the the problem. Apparently the bone into which large amount of work done on the forces act- the prosthesis is inserted manifests creep, so ing on the hip joint while standing on one that the prosthesis moves long before the bone limb and walking. The most recent paper as breaks2'. far as I can determine is that of Williams I wish to thank Miss M Morgan, now a member and Svensson25, who refer to most of the pre- of the Irish Ballet Company, for her willing covious work done on this subject. This is not operation in posing for the ballet photographs, Mrs the place nor have I the competence to deal Jacqueline Charlwood of the Department of Med-
Movements at the hip joint ical Illustration and Photography, Guy's Hospital Medical School, for the photographs of the ballet dancer, Mr K Fitzpatrick, Department of Anatomy, Guy's Hospital Medical School, for his assistance with the illustrations, and Mr K Jackson, Department of Physics, Division of Biological Sciences, Guy's Hospital Medical School, for his help with the biomechanics. I am most grateful to the President and Council of the Royal College of Surgeons of England and Professor R H R McMinn for allowing me to give an Arnott Demonstration.
Sinclair, D C (1972) in Cunningham's Textbook of Anatomy, i Ith edn, ed. Romanes, G J, p. 241. Lonidon, Oxford University Press.
2 Warwick, R, and Williams, P L (I973) in Gray's Anatomy, 35th edn, p. 406. London, Longman. 3 Lane, W A (I898-99) Clinical Journal,
I3, 152.
4 Johnston, T B (1956) Guy's Hospital Reports, 105, 300. 5 Wlheatley, M D, and Jahnke, W D (I95i) Archives of Physical Medicine, 32, 508. 6
Joseph, J, and Williams, P TX (1957) Journal of Anatomy, 91, 286.
7 Joseph, J (I973) in New Developments in Electromyography and Clinical Neurophysiology, c(1. Desmedt, J E, vol. i, p. 665. Basel, Karger. 8 Milch, H
(I959) Journal of Bone and Joint
Surgery, 4IA, 731.
(I'oi)
Anatomical Record, 140, 135. Elftman, H (1939) American Journal of Physiology, 125, 339. i IElftman, H (I967) Biomedical Engineering, 2,
9 Milch, H io
342.
13 14
15 i6
Inman, V T (1947) louirnal of Bone and Joint Surgery, 29A, 607. Strange, F G St C (i965) The Hip, p. 25. London, Heinemann. Keagy, R D, Brumlik, J, anid Bergan, J J (i966) Journal of Bone and Joint Surgery, 48A, 1377. Tonnis, D (I966) Zeitschrift fiur Orthopddie und ihre Grenzgebiete, I02, 6i. Basmajian, J V (1958) Anatomical Record, I32, 127.
References I
12
201
17 McKibbin, B (I968) Journal of Bone and Joint Surgery, soB, i6i. i8 Fitzgerald, P (Ig6g) Irish Journal of Medical Science, 7th series, 2, 31. 19 Joseph, J (I960) Man's Posture. Electromyographic Studies, pp. 79-86. Springfield, Ill., Thomas.
20 Battye, K, and Joseph, J (i966) Medical and Biological Engineering, 4, I25. 2I Report on Fundamental Studies of Human Locomotion Relating to the Design of Artificial Limbs (I947) University of California, San Francisco. 22 Chapman, M W, and Kurokawa, K M (i969) Bulletin of Prosthetics Research, BPR io-II, Spring, 38. 23 Joseph, J, and Watson, R (I967) Journal of Bone and Joint Surgery, 49B, 774. 24 Prosthetic Devices Research Project. Institute of Engineering Research (I953) University of California, Berkeley. 25 Williams, B E, and Sveilsson, N L, (I968) Biomedical Engineering, 3, 365. 26 Schoenfeld, C M, Lautenschlager, E P, and Meyer, P R (I974) Medical and Biological Engineering, 12, 313.
Movements at the hip joint J Joseph
MD DSC FRCOG
Department of Anatomy, Guy's Hospital Medical School, London
Summary Movements at the hip joint are first discussed in terms of free movement of the lower limb on the trunk. The biomechanics of standing on one lower limb limited to the situation
in the coronal plane are presented. The role of the hip muscles in the upright posture and
AN i
in the movements at the hip joint during walking on the flat and upstairs and downstairs is described.
Introduction Although it nay be old-fashioned to use the well-known terms flexion, extension, etc., to describe the movements at a joint, I propose to use them with reference to the movements at the hip because they are well known, easily understood, and in actual fact difficult to replace. I will, however, confine myself to such aspects of movements as are controversial or not well known. In the case of the hip joint, in addition to movements of the lower linmb on the trunk, movements of the trunk on the lower limb have to be considered. It is also necessarv to appreciate the way in which forces act on the hip joint during varioUs activities, but I will limit my remarks on the last-mentioned subject mainly to one particular situation-namely, standing on one lower limb. Movements of lower limb on trunk Flexion at the hip joint is Flexion usually described as being limited, if the leg Arnott Dernonistation given on 24th April 1974
JOSEPHS
N
-
FIG.
named
(A) Arbuthnot Lane, Bexley, Kent, after Sir W Arbuthnot Lane (1856-
surgeon of Guy's Hospital. (B) Joseph's Lane, near Penzance, Cornwall. (This street has no connection with the autthor but it is the best he can do.)
I943), famous
Movements at the hip joint is bent at the knee, by contact of the thigh with the anterior abdominal wall',2. At least 2o0 years ago I suggested that this is quite misleading and that flexion at the hip is limited to about I00° with the leg bent at the knee and that contact between the thigh and the abdominal wall is possible only with the trunk flexed and some additional passive movement at the hip produced by clasping one s arms round the leg and thigh. This observaticn of mine was not original in that W Arbuthnot Lane3 in I896 said, 'On picking up that very excellent text-book Gray's Anatomy I find the following stated deliberately and without reservation of any sort"Flexion of the hip joint is arrested by the soft parts of the thigh and abdominal wall being brought into contact." Now gentlemen, this statement is, except possibly in the case of obese people absolutely without any foundation; in other words, it is uttterly false, as you will see by examining a dissected speciment.' (En passant, there cannot be many Fellows of this College who have a street
I93
named after them. Arbuthnot Lane is in Bexley off the M2 and Lane lived in a house there (Fig. i).) In all fairness I should add that on p. 449 of the same edition of Gray's Anatomy there appears the emendation made by Professor T B Johnston4 as a result of his seeing Lane's article and my confirmation of what Lane said-'Contact of the front of the thigh with the abdominal wall implies supplementary movements at the sacro-iliac [sic], lumbosacral and other intervertebral joints, for it is not usually possible to obtain more than I00° of forward angulation at the joint itself.' Fig. 2 illustrates flexion at the hip in a ballet dancer. I would like to emphasize two points. In B, C, and D it can be seen that her maximum flexion at the hip, whether with the leg straight or bent at the knee or with the lower limb pulled up by the hand, involves some flattening of the lumbar concavity that is, flexion of the trunk. Secondly, in D the additional flexion is associated with some abduction at the hip. It should be pointed out that the main flex-
_C_ FIG. 2 (A) Lateral view of ballet dancer. (B) Flexion of thigh at hip with leg extended at knee. (C) Flexion of thigh at hip with leg flexed at knee. (D) Flexion-abduction of thigh at hip with added passive movement. Note the flattening of the lumbar curvature in B, C, and D.
194
J joseph
of the thigh at the hip are the iliacus and muscles and that all the other muscles described as flexors (rectus femoris, tensor fasciae latae, sartorius, pectineus, some of the adductors) cannot fully and effectively replace paralysed or cut iliacus and psoas muscles. ors
psoas
Extension Extension at the hip from the anatomical position is a very limited movement and even the ballet dancer (Fig. 3) shows very limited extension. It should be noted that in A the lumbar curvature is increased and that the subject is leaning forwards. In B the position of the right lower limb, an attractive arabesque, is almost entirely due to extension of the trunk. The gluteus maximus muscle is always regarded as the main extensor of the thigh at the hip, but if a movement is performed slowly and with limited force it is the hamstrings which are active and the gluteus maximus is recruited for rapid or forceful movement'7. This is shown in the electromyographic record in Fig. 4. The importance of the gluteus maximus in extension of the trunk on the lower limb must be mentioned but will be dealt with more fully when I discuss posture and walking. Abduction Abduction of the lower limb at the hip joint is defined as movement of the limb in the coronal plane away from the body. The main muscles involved are the gluteus medius and gluteus minimus and I would like to emphasize the secondary role of the other muscles (gluteus maximus, tensor fasciae latae, and the short posterior muscles which are mainly lateral rotators). Milch8'9 gives an average figure of 450 for this movement and in Fig. 5B it can be seen that it is rather surprisingly limited in a ballet dancer. However, if she flexes the leg at the knee while at the same time abducting and to some extent flexing the thigh (Fig. 5C) she can then extend the leg and produce the
FVIG. (B)
A
3
(A) Extension of thigh at hip. pparent extension of thigh.
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FIG. 4 Electromyographic recording from hamstrings and gluteus maximus. (A) During slow extension of lower limb at hip. Note that gluteus maximus becomes active towards the end of the movement. (B) Sudden rapid extension of lower limb at hip. Note simultaneous onset of activity in both muscles. Reproduced by permission from New Developments in Electromyography and Clinical Neurophysiology, vol. i-.
Movements at the hip joint position seen in Fig. 5D. This is called de'velope a la seconde and the develope part-that is, the flexing of the leg appears to be an important part in achieving the go9 of abduction seen in Fig. 5C. It should be added that this position of the limnb involves lateral flexion of the trunk. When discussing abduction of the thigh at the hip and the action of the gluteus medius muscle it is more important to refer to the role of this muscle in preventing the opposite, unsupported side from falling when an individual stands on one lower limb. This is seen in every step in walking and going up and down steps. I would like to say something about the forces acting at the hip joint when a subject is standing on one limb. Modem work in this subject is associated with Elftman'0'l' and Inman and his co-workers in the Biomechanics Laboratory in San Francisco12. Inman calculated that when standing on one lower limb the pressure on the head of the femur was about 2.4-2.6 X body weight. This is the resultant of two forces-the body weight and the pull of the abductor muscles,
A
B
C
195
as is shown in Fig. 6. This is also dealt with very fully by Strange in his excellent book on the hip"3. In Fig. 6 the weight of the body minus one lower limb is W and the centre of gravity of this mass is G. The centre of the head of the femur is 0 and the body weight produces a turning movement about O and equals W X OA. The angle APO (200) can be determined. The line of pull by the abductors (PF) can be obtained from the study of X-ray films and cadavers and the ratio of OB:OA is found to be I:2.5. The force exerted by the abductors is therefore .5 X W at an angle of 80. The resultant force PR can now be calculated and is approximately 3.43 X W acting at 200. Certain comments can be made regarding these calculations. Firstly, it is assumed that the head of the femur is a perfect sphere and that 0 can be accurately determined. Seconndly, the shift of the centre of gravity over the supporting limb is very variable. If it is moved directly over the head of the feimur the force exerted by the abductor muscles is reduced to zero. This is unlikely, btut the shorter OA becomes the less force
D
FIG. 5 (A) Posterior view of ballet dancer. (B) Abduction of thigh at hip and (C) flexion of leg at knee as precursor to (D) abduction-flexion of lower limb at hip. Note in D lateral flexion of trunk.
I96
1 Joseph
Body weight minus one lower limb F = Force produced by abductors R = Resultant force on femoral head
W
R FIG. 6 Forces acting on head of femur in coronal plane while subject stands on one lower limb.
is required to be exerted by the abductors, and consequently the less force is applied to the head of the femur.
Adduction The movement of adduction is limited to about I5° according to Milch9, and it is difficult to understand why there is such a relatively large mass of adductor muscles. Nobody seems to be very happy about the explanation that they are used in horse-riding or tree-climbing, and a little thought on their importance in sexual intercourse raises more questions than answers.
Rotation From the anatomical position the extent to which the thigh can be rotated laterally and medially at the hip varies a great deal between individuals, but there is general agreement that these movements are increased considerably if the thigh is flexed. Milch9 gives figures of 6o0 for lateral rotation and 400 for medial rotation with the thigh flexed at the hip. This increase in rotation should be kept in mind because in a clinical examination, with the patient supine on the bed or couch, rotation is estimated with the thigh and leg flexed. Usually the heel is held in one hand and the knee is pushed laterally and medially to estimate the amount of lateral and medial rotation respectively. This also means that the axis of rotation is through the head of the femur and the heel. In the anatomical position the axis is said to be through the head and intercondylar notch of the femur (or lateral or medial condyle, depending on which book one is reading) and the amount of movement is very much less. It is interesting to note that position one in classical ballet involves standing with the feet turned out so that they form a straight linethat is, each lower limb is laterally rotated through 9o0. This is difficult to achieve and is assisted if the dancer first flexes the thighs and legs at the hips and knees, laterally rotates the lower limb as much as possible, usuially to 9o0, and then straightens the thigh and leg. The additional rotation associated with the flexed thigh and the added lateral rotation of the leg at the knee allows rotation of the foot through go9. Anyone attempting this will notice that the inner border of the foot is pressed hard on the ground, so that the lower limb is prevented from turning inwards. There is general agreement that the important lateral rotators are the small muscles on the back of the hip joint (piriformis, obturator internus, and quadratus femoris) as well as
Movements at the hip joint the obturator externus. I was very pleased to be told, although I cannot find the reference, that the main medial rotators are the gluteus minimus and the anterior part of the gluteus medius, and these muscles are assisted bv the tensor fasciae latae. This raises the vexed problem of the action of the iliopsoas muscle. Keagy et al."4 investigated the psoas major muscle by means of intramuscular electrodes through the back and found that it was neither a lateral nor a medial rotator. Tdnnis"', using intramuscular electrodes in the groin, made the same observation, as did Basmajian'6, who put needles into the iliacus muscle. It appears then that the iliopsoas is only a flexor of the thigh in spite of MeKibbin'7 and Fitzgerald'8, who maintain that it is also a lateral rotator. Both Cunningham' and Gray' in their most recent editions do not associate the iliopsoas muscle with rotation except for a passing reference by the latter to the lateral rotation of the femur in fractures of its neck.
Role of muscles of the hip joint while standing at ease This has been extensively investigated (see Josephl9 for list of references). The posture is one in which the weight is on both limbs with the feet about 25 cm apart and pointing comfortably omtwards, and the upper limbs are alongside the trunk or behind the back with the hands lightly clasped. There appears to be general agreement that none of the hip muscles are contracted and this is due to the line of weight of the body above the hip joints falling behind the transverse axis of these joints and the support given by their powerful anterior ligaments. Movements forwards of the centre of gravity of the trunk by swaying forwards or raising the upper limb forwards restults in contraction of the hamstrings, which prevents flexion of the trunk at the hip joints6.
197
Movements at the hip while walking The movements which take place at the hip joints while walking are complex, but they are capable of a degree of analysis. When walking is discussed it is important to accept an agreed description of a step (Fig. 7). A step may be said to begin when the heel strikes the ground (heel strike). This is followed by a stance phase during which the weight is transferred from the heel along the sole to the heads of the metatarsals and then to the plantar surface of the great toe. The lower limb is lifted from the ground (toe off) and enters the swing phase which ends with the heel strike. The stance phase occupies about 3/5ths of the whole step and the swing phase 2/sths. At the beginning and end of the stance phase the opposite limb is on the ground (double stance phases). Each of these occupies about I /5th of the whole step. The most obvious movement at the hip is extension during the stance phase and flexion during the swing phase. It is interesting that both gluteus maximus and the hamstrings contract during only the first half of the stance phase-that is, until the trunk is vertically over the hip joint-and stop contracting during the second half of this phase20. With the foot on the ground the forward momentum of the body produces sufficient force to continue the extension at the hip. The contraction of the gluteus maximus and hamstrings may pull the trunk over the supporting limb in the early stance phase or prevent the trunk flexing at the hip, as suggested by Strange'3. In a somewhat similar way the iliopsoas contracts during only the first part of flexion at the hip in the swing phase20. I would like to quote Keagy et al.'4 on this-'While walking forward, activity regularly appeared 8o to I20 ms before toe off, and persisted only during the initial 40%/0 of the swing phase. This indicates and confirms that the prime
I98
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function of this muscle in gait is to initiate and accelerate the forward advancement of the limb. Once motion is started, the muscle rests'. There is no evidence that during the second half of the stance phase the flexors of the hip are active to carry the trunk along with the hip and rotate the pelvis forwards at the hip of the supporting limb, as suggested by Straqrge`. There is no need for me to dilate on the role of the abductors (gluteus medius and minimus and tensor fasciae latae) during the stance phase. Their contraction prevents the falling of the body to the unsupported side. The role of the adductors in walking has been investigated by only one group of workers, whose pioneer studies in the electromyography of muscles used in gait cannot go unmentioned21. They found marked activity of the adductors at the end of the stance phase and also a smaller peak of activity at the beginning of the same phase. They related these periods
of activity to the stabilizing of the pelvis on the femora during the period of double support and controlling horizontal rotation of the pelvis. Activity of the adductors, however, is seen at the beginning and end of the swing phase and it is suggested that the adductors control the frontal plane movements of the lower limb during this phase. It is usually assumed that lateral rotation of the lower limb takes place during the swing phase. This could be due to contraction of the small muscles at the back of the hip joint, but these have not been investigated. The San Francisco workers think that this rotation may be due to the adductors. In many individuals as the heel rises and the weight is on the anterior part of the the sole the heel is seen to move inwards-that is, a lateral rotation takes place. The adductors or the gluteus maximus may produce this. Of more importance is the medial rotation of the pelvis on the lower limb during the
Movements at the hip joint
flexed at the hip and the knee and the body is lifted upwards by straightening the limb. The extension at the hip is due to marked contraction of the hamstrings and gluteus maximus and this activity continues until the opposite limb is placed on the next step. There is a phase of single limb support while the limb is being straightened and, as expected, this is accompanied by contraction of the gluteus medius. The iliopsoas is contracted during the whole of the swing phase-that is, when the limb is being flexed at the hip and knee and lifted on to the step above. On going downstairs the lowering of the body to the next step is achieved by the controlled lengthening of the soleus and quadriceps femoris. There is only a very short contraction of the gluteus maximus at the beginning of the stance phase, and the hamstrings are briefly contracted to flex the leg at the knee in the middle of the swing phase.
stance phase. This increases the length of the step and is essential because of the limited extension possible at the hip joint. The muscles which cause medial rotation (the gluteus minimus, tensor fasciae latae, and anterior part of the gluteus medius) are contracted during this phase to prevent the body falling to the unsupported side. This medial rotation is said to be more marked in the female sex. It has been shown by Chapman and Kurokana22 that there is a 'quantitative similarity between the average pelvic and shoulder rotations in the two sexes. Observations of men's and women's gait patterns led Us to expect a greater amplitude of individual transverse rotations in women. On the contrary, most of the greatest individual rotations measured occurred in men.' Joseph and Watson (Figs. 8 and 9) have shown that when going upstairs the lower limb which is placed on the step above is
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The gluteus medius, as expected, is con- with the complicated calculations involved in tracted during the single stance phase. It is estimating the forces acting on the hip joint, interesting to note that the trunk is kept al- but one is struck by the differences in the remost vertically above the thigh during the sults obtained by various investigators who stance phase so that there is minimal or no state that the force acting on the head of contraction of the flexors and extensors at the the femur while standing on one limb ranges hip. All these observations in relation to going from 2.4 to 6.o X body weight and while upstairs and downstairs confirmed those made walking from 2.5 to 6.o X body weight. That in a somwehat inaccessible report published a correct estimation of the forces involved is of paramount importance is obvious to anyin 195324. one interested in the hip joint and especially its replacement, but I am now told that the Conclusion One cannot end this lecture on movements strength of the prosthesis is only one part of at the hip joint without a reference to the the problem. Apparently the bone into which large amount of work done on the forces act- the prosthesis is inserted manifests creep, so ing on the hip joint while standing on one that the prosthesis moves long before the bone limb and walking. The most recent paper as breaks2'. far as I can determine is that of Williams I wish to thank Miss M Morgan, now a member and Svensson25, who refer to most of the pre- of the Irish Ballet Company, for her willing covious work done on this subject. This is not operation in posing for the ballet photographs, Mrs the place nor have I the competence to deal Jacqueline Charlwood of the Department of Med-
Movements at the hip joint ical Illustration and Photography, Guy's Hospital Medical School, for the photographs of the ballet dancer, Mr K Fitzpatrick, Department of Anatomy, Guy's Hospital Medical School, for his assistance with the illustrations, and Mr K Jackson, Department of Physics, Division of Biological Sciences, Guy's Hospital Medical School, for his help with the biomechanics. I am most grateful to the President and Council of the Royal College of Surgeons of England and Professor R H R McMinn for allowing me to give an Arnott Demonstration.
Sinclair, D C (1972) in Cunningham's Textbook of Anatomy, i Ith edn, ed. Romanes, G J, p. 241. Lonidon, Oxford University Press.
2 Warwick, R, and Williams, P L (I973) in Gray's Anatomy, 35th edn, p. 406. London, Longman. 3 Lane, W A (I898-99) Clinical Journal,
I3, 152.
4 Johnston, T B (1956) Guy's Hospital Reports, 105, 300. 5 Wlheatley, M D, and Jahnke, W D (I95i) Archives of Physical Medicine, 32, 508. 6
Joseph, J, and Williams, P TX (1957) Journal of Anatomy, 91, 286.
7 Joseph, J (I973) in New Developments in Electromyography and Clinical Neurophysiology, c(1. Desmedt, J E, vol. i, p. 665. Basel, Karger. 8 Milch, H
(I959) Journal of Bone and Joint
Surgery, 4IA, 731.
(I'oi)
Anatomical Record, 140, 135. Elftman, H (1939) American Journal of Physiology, 125, 339. i IElftman, H (I967) Biomedical Engineering, 2,
9 Milch, H io
342.
13 14
15 i6
Inman, V T (1947) louirnal of Bone and Joint Surgery, 29A, 607. Strange, F G St C (i965) The Hip, p. 25. London, Heinemann. Keagy, R D, Brumlik, J, anid Bergan, J J (i966) Journal of Bone and Joint Surgery, 48A, 1377. Tonnis, D (I966) Zeitschrift fiur Orthopddie und ihre Grenzgebiete, I02, 6i. Basmajian, J V (1958) Anatomical Record, I32, 127.
References I
12
201
17 McKibbin, B (I968) Journal of Bone and Joint Surgery, soB, i6i. i8 Fitzgerald, P (Ig6g) Irish Journal of Medical Science, 7th series, 2, 31. 19 Joseph, J (I960) Man's Posture. Electromyographic Studies, pp. 79-86. Springfield, Ill., Thomas.
20 Battye, K, and Joseph, J (i966) Medical and Biological Engineering, 4, I25. 2I Report on Fundamental Studies of Human Locomotion Relating to the Design of Artificial Limbs (I947) University of California, San Francisco. 22 Chapman, M W, and Kurokawa, K M (i969) Bulletin of Prosthetics Research, BPR io-II, Spring, 38. 23 Joseph, J, and Watson, R (I967) Journal of Bone and Joint Surgery, 49B, 774. 24 Prosthetic Devices Research Project. Institute of Engineering Research (I953) University of California, Berkeley. 25 Williams, B E, and Sveilsson, N L, (I968) Biomedical Engineering, 3, 365. 26 Schoenfeld, C M, Lautenschlager, E P, and Meyer, P R (I974) Medical and Biological Engineering, 12, 313.
