Fortschr. Rönrgenstr. 125, 5
399
Fortschr. Röntgenstr. 125, 5 (1976) 399-404 © Georg Thieme Verlag, Stuttgart
Landmarks of the knee joint on the lateral Radiograph during rotation' By K. Jacobsen S Figures Department of orthopaedic Surgery T-3 and Department of Diagnostic Radiology. The Gentofte Hospital, Copenhagen
On specimens of human knee joints a study was made of the contours on the lateral radiograph during rotation up to 450 inwards and outwards. The most important characteristics of the femoral condyles are the situation of the limiting groove on the condylar joint surface. The best for identifying the tibial condyles is the lateral intercondylar tubercie which proceeds backwards in an even, convex arch continuing direct in the posterior contour of the lateral tibial condyle. Introduction It is of decisive importance in measurements on the lateral radiograph of the knee joint that the structures of the joint can be accurately identified on the film. In particular, the Aided by grants from the Danish Medical Research Council, the Danish Council for Sport Research, and the foundation for the Handicapped.
Merkmale am Knie auf seitlichen, rotierenden Röntgenaufnahmen
Die Konturen von anatomischen Präparaten am menschlichen Knie wurden auf seitlichen Röntgenaufnahmen bei 45° jeder Drehung studiert. Das wichtigste Merkmal der unteren Femora ist die begrenzende Furche auf der Gelenkoberfläche. Das beste Zeichen am Kondyl der Tibia ist das äußere Tuberkulum, welches sich in einem gleichmäßigem, konvexem Bogen bewegt, der in die hintere Kontur des äußeren (F. St.) Kondyl einschmelzt.
description of the outlines of the femoral and tibial condyles is important for any measurement of anteposterior instability (drawer sign) (Jacobsen, 1976). The three-dimensional object, the knee joint, is projected to a
two-dimensional picture, giving contours and condensed lines on the picture where cortical bone (Lachmann, 1937) or
the bone-cartilage junction (Weiss, 1943; Stückelberger, 1944) are hit tangentially by the roentgen beam. Accordingly,
This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.
K. Jacobsen: Landmarks of the knee joint on the lateral Radiograph during rotation
Fortschr. Röntgenstr. 125, 5
K. Jacobsen
The apparatus designed to obtain an exact degree of rotation from the neutral position (on the figure) of knee joint specimens in a constantly directed roentgen beam. Specimen fastened to the pole in the centre of the turntable. Right knee joint. On the grading scale the meaning of external (outw.) (fibular) and internal (mw.) (tibial) rotation for this specimen. Fig. 1.
Radiograph showing a far more pronounced condyl-
Fig. 2.
opatellar sulcus on the medial, b, than on the lateral, a, femoral condyle. Nevertheless the characteristic localization of the sulcus on each condyle makes identification possible.
Od
I. Fig. 3a Profile of the proximal end of tibia on the lateral radiograph. Unbroken lines (on the right): Lateral tibial condyle and lateral intercondylar tubercle. Broken lines: Medial tibial condyle Figs. 3 a and b.
and medial tubercle. Dotted lines: Anterior tibial margin, tibial
tuberosity, crest of anterior intereondylar area, a, and digital tibial impression, b. Small circles: Head of fibula.
these contours and lines change on rotation of the object. This necessitates experimental identification of the contours in the various positions of rotation, which has not hitherto been performed. The present author carried out an experimental study of the knee joint landmarks in different projections, during rotation
of knee-joint specimens with a constant direction of the beam. As all the knee-contours had to be studied simultaneously and their relations be compared the method of leadmarking was chosen instead of tomography.
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Fig. 3b
patella, and inferior patellar ligament were removed. They were marked with pins and lead marks and radiographed in different positions of rotation. Ten of the specimens were studied systematically in a special apparatus (Fig. 1). The specimens were fastened
to a pole in the centre of a turntable surrounded by a grading scale. A pointer indicated the rotation from neutral position or "zero position". This was defined as the position in which the distal contours - meaning in 9Ø0 of flexion the anterior contours - of the two femoral condyles were projected on top of each other on the film, i.e. the two femoral condyles were hit tangentially by the same beam. Standard views were exposed
A total of 14 human knee-joint specimens were stripped, pre-
with a latero-medial direction of the beam, but control exposures with medio-lateral direction of the beam revealed that this does not influence the landmarks mentioned below. After exposure in neutral position, new exposures were made in 50, 100, 15°, 30°, and 45° rotation, internal and external, and a control exposure
serving all ligaments and both menisci intact, whereas the capsule,
in the a-p projection to substantiate the position of the lead
Material and method
This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.
400
Fortschr. Röntgenstr. 125, 5
Landmarks of the knee joint on the lateral Radiograph during rotation
401
marks. The exposure were made with 48-52 kV for 0.04 sec with a raster in the casette. Distance from tube to casette: 1 m. The following anatomical structures were studied: Both femoral condyles have a limiting groove (Grenzrinne).
With extended knee joint the anterior parts of the respective
the intercondylar area, situated between the tibial condyles. This is divided into the anterior intercondylar area, the intercondylar eminence, and the posterior intercondylar area. The intercondylar eminence consists of the medial and lateral intercondylar tubercles, connected by a ridge, the intertubercular crest. The anterior inrercondylar area is divided by a ridge proceeding in the antero-posterior direction, the anterior crest of the intercondylar area, in a medial plateau, and a lateral, deeper lying depression (Negru, 1943). There may be a welldeveloped bony prominence, Parsons' knob or tubercle, corresponding to the anteromedial part of the insertion of the anterior cruciate ligament (Parsons, 1906). Fig. 4.
Description and results On the lateral radiograph the contours of the two femoral condyles differ as follows: The patellar surface of the femur starts more proximally (10-12 mm) on the lateral than on the medial femoral condyle. Correspondingly, the large guiding ridge for the patella on the lateral femoral condyle starts proximally to the medial femoral condyle. The limiting groove is present on the radiograph of both femoral condyles in very different shapes, as described by Ravelli (1949): As a notch in the condylar contour or merely as an intersection between two curved lines.
The situation of the groove on the condylar contour is constant and characteristic. On the lateral condyle the groove
is about midway on the curvature of the total joint surface, but on the medial condyle far more proximally, anteriorly at
the junction of the proximal third and distal two-thirds. As a rule, the groove is clearer on the lateral femoral condyle, but the reverse may also apply (Fig. 2).
Present investigations: As regards the shape of the contours of the groove, all the shapes sketched by Ravelli were observ-
ed, and a motley mixture of intermediate shapes. It was investigated whether the shape on the lateral and medial femoral condyle respectively depended regularly upon the degree of rotation in relation to the central beam. This was not so; the appearances were completely predominated by individual variations. On the specimens studied the grooves were demonstrable radiologically on both condyles in all cases. On a few exposures one was absent. They are most
clearly visualized in the neutral position and up to 100 rotation, external and internal. The patellar surface of the femur is traced posteriorly to the anterior proximal contours of the femoral condyles as a fairly condensed line which meets, in an almost right angle, the line representing the tangentially hit part of the "roof" in the intercondylar femoral fossa, Blumensaat's line (1938). The origin of this line may be demonstrated by marking with a strip of lead (or by tomography. Fagerberg, 1956). Present investigations: The situation of Blumensaat's line on the lateral radiograph is extremely sensitive to changes in
The contour of the posterior part of the lateral tubercie
(arrow) visible as a soft curve. Right tibia in 450 external rotation.
Note that in this position the contour does not continue in the most posterior contour of the lateral tibial condyle.
position (on average 330), whereas it increases on external as
well as internal rotation (up to 55°). For description of Ludloff' triangle (1903) refer to Fagerberg (1956).
On the tibia, in the intercondylar area (Fig. 3), the medial tubercle anteriorly raises its contour above the level of the joint surface (at point A) earlier than the lateral tubercle and proceeds, in an even slope, to its peak whence it falls posteri-
orly rather abruptly towards the posterior intercondylar fossa. The medial tubercie, in most cases the taller one (Mouchet and Noureddine, 1925; Schlüter and Becker, 1955; Jonasch, 1958) is thus discernible by having only one peak, shaped as an even curve and an abrupt fall posteriorly. The lateral tubercle starts behind the medial tubercle, rising to a pronounced anterior peak, but thereafter proceeds in an
even curve, often after a small notch, posteriorly until reaching the posterior contour of the lateral tibial condyle. Anatomically this junction of the lateral tubercle and lateral condyle is at the postero-medial corner of the socket of the lateral tibial condyle (Jacobsen, 1974). Thus, the lateral tubercle has two curves or peaks. In some cases there is still, just anterior or posterior to the
posterior contour of the medial tubercie a faint contour representing the posterior wall of the intertubercular crest. Present investigations: The most characteristic landmark of the tubercles, the posterior arch of the lateral tubercle, is visualized most clearly in increasing external rotation. At a 30° to 450 external rotation this arch is still clearly visible, but now the posterior contour of the lateral tibial condyle is made up by a more laterally situated part of the posterior
surface of the condyle, so that now it is not possible to observe the direct course of the posterior arch of the lateral tubercle onwards in the posterior condylar contour (Fig. 4). At 5°-10° internal rotation the posterior arch of the lateral
tubercle is superimposed on the posterior contour of the
medial tubercle, and at 15°-30° internal rotation it
is
position in relation to the central beam, the "roof" of the
visible in front of it.
intercondylar femoral fossa being curved in several directions,
The crest of the anterior intercondylar area, described by
so that different parts of this curved roof will be hit tangentially by the rays, depending upon the position of rotation of the knee joint. Thus, the angle between Blumensaat's line and the axis of the femoral shaft is least around the neutral
Negru, forms a contour on the radiograph. It may be discerned in the neutral position, but grows more distinct on internal
rotation. At 30° and 45° internal rotation and from 30° of external rotation it is hidden by the condyles.
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menisci are situated in these sulci (on all specimens) in agreement with Fick (1904). The joint surfaces of the tibial condyles and
402
Fortscht. Röntgenstr. 125, S
K. Jacobsen Figs. Sa and b. Radiograph of the same specimen in 15° external rotation (Sa) and 45° external rotation (Sb). Medial tibial condyle with the long lead strip most distally, both on the anterior and posterior
aspect. Lateral tibial condyle with a shorter strip. The sketches show the relation of the fibular head to the condyles of the tibia: unbroken lines: fibula and lateral condyle and tubercie. Broken lines: medial condyle and tubercle. Note that in 5 a the capitulum
flbulae may be mistaken to articulate with the big, squared (medial) condyle - and that this mistake is unmasked in 5 b. Note also the course of the posterior arch of the lateral and
Fig. 5a
Fig. Sa2
Fig. Sb1
At the middle of the anterior intercondylar area on the lateral
radiograph Parsons' knob is in some cases delineated as a triangular contour. On a specimen the anterior edge of the soft-tissue shadow of the anterior cruciate ligament may be
Present investigations: By marking, it can be demonstrated that the proximal limit of the insertion area on the lateral radiograph (in neutral position) corresponds to the point of intersection between the sharp contour of this area and the contour of the articular socket of the medial tibial condyle. The bone contours of the lateral condyle are either entirely
traced to its insertion on this peak. The prominence is present on the radiographs of 4 out of the 14 specimens (also on Fig. 3). Parsons' knob is thus identical with the linear or most often slightly convex, in a few slightly concave. prominence described by Politzer & Pick (1937) known in radiological literature as the "tuberculum intercondylare tertium".
The bone contour of the medial condyle is always concave.
The posterior intercondylar area gives a sharp contour
anterior part of the more oblique medial articular surface is situated above the level of the lateral one. However, this appearance is very apt to get distorted on tilting of the bone in the frontal plane in relation to the central beam.
which may be found by tracing the posterior contour of the medial tubercie downwards and backwards, where it dips down between the two tibial condyles (Fig. 3). This area being equal to the insertion facet of the posterior cruciate ligament which is distinctly defined on a macerated specimen of the bone (Jacobsen 1974).
The bone contour of the lateral articular surface is more high-seated in the majority of cases. Only the very most
Present investigations: Anteriorly, the contour of the crest of the anterior intercondylar area (Negru) is of a varying situa-
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medial tubercle.
Landmarks of the knee joint on the lateral Radiograph during rotation
The posterior contour of the lateral tibial condyle may be found by tracing the posterior convex, curved part of the
403
ward. In cases of severe abnormalities, however, a greater rotation is possible. Therefore, the present study of the kneejoint landmarks during rotation has been necessary. The contours of the femoral condyles, especially the limiting grooves, were studied by Ravelli - but without investigation
lateral tubercle. Then it may be traced forwards in the convex line of the socket contour. However, the lateral tibial condyle may form 2 or 3 densely placed, more or less sharply delimited contours (two on Fig. 3). The posterior contour of the medial
of the influence of rotation. His findings are confirmed by the present author. I also share Ravelli's opinion that the shadow
tibial contour is found, in the neutral position, behind the
so seldom present (in 10% of Ravelli's cases and in 13% of Falk's [1963]). Moreover, it may be confused with an ossification centre in the medial head of the gastrocnemius muscle which is a very uncommon occurrence (Kremser, 1930; Freyer, 1960). The adductor tubercie is also of limited value,
contour of the lateral condyle. The proximal, posterior point, B on Figure 3, represents the point of intersection of the two contours of the medial joint socket. The medial tibial condyle is large and squared-off, whereas the contour of the lateral condyle is more slender.
Present investigations: On rotation of the specimen this characteristic condylar shape remains unchanged. On medial rotation it grows ever more distinct that the head of the fibula is not in contact with the squared-off contour. From 5° to 30°
external rotation the appearances may give the erroneous impression that the head of the fibula articulates with the large squared-off condylar contour. It is not until at 45° external rotation that it is disclosed that articulation takes place with the more pointed contour which is thereby unmasked as the lateral condylar contour (Fig. S). Thus, the head of the fibula is a poor landmark for determining the condylar contours (especially from 5°-30° external rotation which is common on clinical lateral radiographs). The insertions of the soft tissues in the intercondylar tibial areas may be determined on the lateral radiograph: Where Parsons' knob or tubercle is present the insertion of the anterior cruciate ligament is from the top of this knob and down its posterior surface, further backwards to the top of the medial tubercie. The anterior horn of the medial meniscus
inserts on the anterior, declining surface of Parsons' knob. If the latter is not present, the anterior horn of the meniscus inserts in the area between the crest of the anterior intercondylar area and the anterior superior edge of the medial articular socket. This slightly excavated facet Negru called
the "impressio digitalis tibiae". Just posterior to it the insertion of the ligament starts. The demarcation of the insertion facet for the posterior cruciate ligament, has been described above. The posterior horn of the medial meniscus inserts on a small facet on the posterior declining contour of the medial tubercle proximally to the contour of the medial articular socket. The posterior horn of the lateral meniscus inserts on the top of the intertubercular crest. The insertion
of the anterior horn of the lateral meniscus can not be accurately localized, but the facet is just anterior to the beginning of the lateral tubercle anteriorly. The anterior limit of the origin of the posterior cruciate ligament from the intercondylar femoral fossa is localized at the anterior point of Blumensaat's line. The posterior limit of the origin of the
anterior cruciate ligament from the intercondylar femoral fossa is found at the posterior angulation of Blumensaat's line.
Discussion With the gonylaxometer - an apparatus for radiological measurement of the drawer sign by hydraulic action on the knee joint (Jacobsen, 1976) - the first exposure (unloaded, 90° flexed knee) is made in a position very close to what is defined here as "neutral" or "zero" position. Rotation of the tibia during traction and pressure amounts in the predominant majority of cases to less than about 15° inward or out-
of the fabella, situated in the lateral head of the gastrocnemius muscle, is of limited value as a landmark, because it is
as it is rarely distinguishable from muscle traces at the
insertion of the medial and lateral heads of the gastrocnemius muscle (Lachmann 1937).
Teichert (1955) has described yet another means of determining the side of the femoral condyles on the lateral radiograph : In the lateral part of the femoro-patellar joint the femoral and patellar contours proceed for a longer distance parallel than in the medial part of this joint. This sign is pronounced in "intermediate flexion". In studies at 90° flexion it may lead to errors. The femoral condyles are easy identified - also on Teichert's figures - by the situation of the limiting groove. Kennedy & Fowler (1971), who used lateral radiographs for
measuring anterior instability in the knee joint, do not mention the groove on the medial femoral condyle, where it may be just as pronounced, or more so, than on the lateral.
Nor do they mention the situation of the grooves on the articular surfaces. The conclusion is that reliable landmarks for identifying the
femoral condyles on the lateral radiograph are: The lateral femoral condyle has a far larger guiding ridge for the patella than the medial condyle. On the lateral femoral condyle the limiting groove is situated at about the middle of the articular surface, but on the medial condyle within its anterior, proximal third. According to Kennedy & Fowler the lateral tibial condyle "is identified by its more squared-off posterior projection". On their Figure 20 and its legend they thus misinterpret the posterior contour of the medial tibial condyle as that of the lateral. The results of their measurements are questionable, as these landmarks were used in measuring the drawer sign in the knee joint.
It may be concluded that the following landmarks are applicable for identifying the tibial condyles: The lateral intercondylar tubercie proceeds backwards from its peak in an even, convex arch continuing direct in the posterior contour of the lateral tibial condyle. The medial tubercle slopes from its peak rather steeply downward and backward in a straight or concave line towards the posterior intercondylar area.
The proximal, posterior corner of the medial tibial condyle is formed by the meeting of the two arcuate contours
of the outer and inner demarcation of the articular socket. The posterior contour of the lateral tibial condyle is more pointed and more slender than the large squared-off contour of the medial condyle. On more than 900 lateral radiographs exposed in the gonylaxometer there has never been a lack of these landmarks in sufficient numbers for identification of the condyles. A description of the relation of the ligamentous and menis-
ceal insertions to the contours on the lateral radiograph
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tiOn: below the levels of both joint surfaces, between them or above both. The latter is very uncommon (seen in only one out of the 14 specimens).
Fortschr. Röntgenstr. 125, 5
M. Friedrich u. Mitarb.
Fortschr. Röntgenstr. 125, 5
is of particular importance in cases of abnormalities where
im lateralen und medialen Gastrocne-
avulsions of bone may be found in the sites concerned.
mius-Kopf. Röntgenpraxis 2 (1930) 134
Moreover, it may be of importance in interpreting an arthrography with reference to cruciate ligament damage.
Lachmann, E.: The roentgen anatomy
of the knee joint. An experimental
Literature Blumensaat, C.: Die Lageabweichungen und verrenkungen der Kniescheibe.
Ergebn. Chir. Orthop. 31 (1938) 149 Fagerberg, S.: Tomographic studies on
the normal and injured knee. Acta radiol. Suppl. 138 (1956) Falk, G. D.: Radiographic observations of the incidence of Fabella. Bull. Hosp. Jt Dis. (N. Y.). 24, (1963) 127 Fick, R.: Handbuch der Anatomie und
Mechanik der Gelenke.
IllI.
In: Handbuch der Anatomie des Menschen.
von K. von Bardeleben. Band Il, Teil I p 352 und p 343 und Teil Ill p 569. Fischer, Jena 1904 Freyer, B.: Beobachtung einer Fabella im medialen Gastrocnemiuskopf. Fortschr. Röntgenstr. 92 (1960) 469
Jacobsen, K.: Area intercondylaris tibiae. Osseous surface structure and its
relation to soft tissue structures and applications to radiography. J. Anat.
analysis. Radiology. 29 (1937) 455 Ludloff, K.: Uber Wachstum und Architektur der unteren Femurepiphyse und oberen Tibiaepiphyse. Btuns' Beitr. kIm. Chir. 38 (1903) 64 Mouchet, A., A. Noureddine: Note sur
l'épine du tibia. Bulletins et memoires
(Lond.( 117 (1974) 605; Stress radiographical measurement of antero-posterior, medial and lateral stability in the knee (oint. Acta orthop.
de la société anatomique (Paris). 95
scand. 47 (1976) 335
str. 68 (1943) 194
Ravelli, A.: Zum Röntgenbild des menschlichen Kniegelenkes. Fortschr. Röntgenstr. 71)1949) 614
Schlüter, K., R. Becker: Die Form der Eminentia intercondylica tibiae. Arch. orthop. Unfall-Chir. 47 (1955) 703 Stückelberger, P.: Die Beteiligung der verkalkten Knorpelgrundschichte an der Bildung der röntgenologischen
(1925) 58
Gelenklinie. Radiol. clin. XIII (1944)
Negru, D.: Beitrag zum Studium der
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normalen Anatomie des Kniegelenkes im Röntgenbilde. Fortschr. Röntgen-
Teichert, G.: Beitrag zur RöntgenbildAnalyse des Kniegelenkes. Röntgenblätter 8 (1955) 4
Jonasch, E.: Untersuchungen über die Form der Eminentia intercondyloidea tibiae im Röntgenbild. Forrschr. Röntgenstr. 89 (1958) 81 Kennedy, J. C., P. J. Fowler: Medial and anterior instability of the knee. An anatomical and clinical study using stress machines. J. Bone Jt Surg. 53A
Parsons, F. G.: Observations on the head of the tibia. J. Anat. Physiol.
(1971) 1257
58,
Kremser, K.: Beobachtung einer Fabella
genologisch wichtigen Knochenbefund am medialen Kondylus der Tibia. Fortschr. Rönrgenstr. 56 (1937) 649
(Lond.) vol. XLI (1906) 83 Politzer, G., J. Pick: Uber einen rönt-
K. Jacobsen, Søndertoften, 2630 Tãstrup, Denmark
Weiss,
K.:
Die
Knorpel-Knochen-
Grenze der Pars constituens articuli im Röntgenbild. Fortschr. Röntgenstr. 67 (1943) 26
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404
399
Fortschr. Röntgenstr. 125, 5 (1976) 399-404 © Georg Thieme Verlag, Stuttgart
Landmarks of the knee joint on the lateral Radiograph during rotation' By K. Jacobsen S Figures Department of orthopaedic Surgery T-3 and Department of Diagnostic Radiology. The Gentofte Hospital, Copenhagen
On specimens of human knee joints a study was made of the contours on the lateral radiograph during rotation up to 450 inwards and outwards. The most important characteristics of the femoral condyles are the situation of the limiting groove on the condylar joint surface. The best for identifying the tibial condyles is the lateral intercondylar tubercie which proceeds backwards in an even, convex arch continuing direct in the posterior contour of the lateral tibial condyle. Introduction It is of decisive importance in measurements on the lateral radiograph of the knee joint that the structures of the joint can be accurately identified on the film. In particular, the Aided by grants from the Danish Medical Research Council, the Danish Council for Sport Research, and the foundation for the Handicapped.
Merkmale am Knie auf seitlichen, rotierenden Röntgenaufnahmen
Die Konturen von anatomischen Präparaten am menschlichen Knie wurden auf seitlichen Röntgenaufnahmen bei 45° jeder Drehung studiert. Das wichtigste Merkmal der unteren Femora ist die begrenzende Furche auf der Gelenkoberfläche. Das beste Zeichen am Kondyl der Tibia ist das äußere Tuberkulum, welches sich in einem gleichmäßigem, konvexem Bogen bewegt, der in die hintere Kontur des äußeren (F. St.) Kondyl einschmelzt.
description of the outlines of the femoral and tibial condyles is important for any measurement of anteposterior instability (drawer sign) (Jacobsen, 1976). The three-dimensional object, the knee joint, is projected to a
two-dimensional picture, giving contours and condensed lines on the picture where cortical bone (Lachmann, 1937) or
the bone-cartilage junction (Weiss, 1943; Stückelberger, 1944) are hit tangentially by the roentgen beam. Accordingly,
This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.
K. Jacobsen: Landmarks of the knee joint on the lateral Radiograph during rotation
Fortschr. Röntgenstr. 125, 5
K. Jacobsen
The apparatus designed to obtain an exact degree of rotation from the neutral position (on the figure) of knee joint specimens in a constantly directed roentgen beam. Specimen fastened to the pole in the centre of the turntable. Right knee joint. On the grading scale the meaning of external (outw.) (fibular) and internal (mw.) (tibial) rotation for this specimen. Fig. 1.
Radiograph showing a far more pronounced condyl-
Fig. 2.
opatellar sulcus on the medial, b, than on the lateral, a, femoral condyle. Nevertheless the characteristic localization of the sulcus on each condyle makes identification possible.
Od
I. Fig. 3a Profile of the proximal end of tibia on the lateral radiograph. Unbroken lines (on the right): Lateral tibial condyle and lateral intercondylar tubercle. Broken lines: Medial tibial condyle Figs. 3 a and b.
and medial tubercle. Dotted lines: Anterior tibial margin, tibial
tuberosity, crest of anterior intereondylar area, a, and digital tibial impression, b. Small circles: Head of fibula.
these contours and lines change on rotation of the object. This necessitates experimental identification of the contours in the various positions of rotation, which has not hitherto been performed. The present author carried out an experimental study of the knee joint landmarks in different projections, during rotation
of knee-joint specimens with a constant direction of the beam. As all the knee-contours had to be studied simultaneously and their relations be compared the method of leadmarking was chosen instead of tomography.
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Fig. 3b
patella, and inferior patellar ligament were removed. They were marked with pins and lead marks and radiographed in different positions of rotation. Ten of the specimens were studied systematically in a special apparatus (Fig. 1). The specimens were fastened
to a pole in the centre of a turntable surrounded by a grading scale. A pointer indicated the rotation from neutral position or "zero position". This was defined as the position in which the distal contours - meaning in 9Ø0 of flexion the anterior contours - of the two femoral condyles were projected on top of each other on the film, i.e. the two femoral condyles were hit tangentially by the same beam. Standard views were exposed
A total of 14 human knee-joint specimens were stripped, pre-
with a latero-medial direction of the beam, but control exposures with medio-lateral direction of the beam revealed that this does not influence the landmarks mentioned below. After exposure in neutral position, new exposures were made in 50, 100, 15°, 30°, and 45° rotation, internal and external, and a control exposure
serving all ligaments and both menisci intact, whereas the capsule,
in the a-p projection to substantiate the position of the lead
Material and method
This document was downloaded for personal use only. Unauthorized distribution is strictly prohibited.
400
Fortschr. Röntgenstr. 125, 5
Landmarks of the knee joint on the lateral Radiograph during rotation
401
marks. The exposure were made with 48-52 kV for 0.04 sec with a raster in the casette. Distance from tube to casette: 1 m. The following anatomical structures were studied: Both femoral condyles have a limiting groove (Grenzrinne).
With extended knee joint the anterior parts of the respective
the intercondylar area, situated between the tibial condyles. This is divided into the anterior intercondylar area, the intercondylar eminence, and the posterior intercondylar area. The intercondylar eminence consists of the medial and lateral intercondylar tubercles, connected by a ridge, the intertubercular crest. The anterior inrercondylar area is divided by a ridge proceeding in the antero-posterior direction, the anterior crest of the intercondylar area, in a medial plateau, and a lateral, deeper lying depression (Negru, 1943). There may be a welldeveloped bony prominence, Parsons' knob or tubercle, corresponding to the anteromedial part of the insertion of the anterior cruciate ligament (Parsons, 1906). Fig. 4.
Description and results On the lateral radiograph the contours of the two femoral condyles differ as follows: The patellar surface of the femur starts more proximally (10-12 mm) on the lateral than on the medial femoral condyle. Correspondingly, the large guiding ridge for the patella on the lateral femoral condyle starts proximally to the medial femoral condyle. The limiting groove is present on the radiograph of both femoral condyles in very different shapes, as described by Ravelli (1949): As a notch in the condylar contour or merely as an intersection between two curved lines.
The situation of the groove on the condylar contour is constant and characteristic. On the lateral condyle the groove
is about midway on the curvature of the total joint surface, but on the medial condyle far more proximally, anteriorly at
the junction of the proximal third and distal two-thirds. As a rule, the groove is clearer on the lateral femoral condyle, but the reverse may also apply (Fig. 2).
Present investigations: As regards the shape of the contours of the groove, all the shapes sketched by Ravelli were observ-
ed, and a motley mixture of intermediate shapes. It was investigated whether the shape on the lateral and medial femoral condyle respectively depended regularly upon the degree of rotation in relation to the central beam. This was not so; the appearances were completely predominated by individual variations. On the specimens studied the grooves were demonstrable radiologically on both condyles in all cases. On a few exposures one was absent. They are most
clearly visualized in the neutral position and up to 100 rotation, external and internal. The patellar surface of the femur is traced posteriorly to the anterior proximal contours of the femoral condyles as a fairly condensed line which meets, in an almost right angle, the line representing the tangentially hit part of the "roof" in the intercondylar femoral fossa, Blumensaat's line (1938). The origin of this line may be demonstrated by marking with a strip of lead (or by tomography. Fagerberg, 1956). Present investigations: The situation of Blumensaat's line on the lateral radiograph is extremely sensitive to changes in
The contour of the posterior part of the lateral tubercie
(arrow) visible as a soft curve. Right tibia in 450 external rotation.
Note that in this position the contour does not continue in the most posterior contour of the lateral tibial condyle.
position (on average 330), whereas it increases on external as
well as internal rotation (up to 55°). For description of Ludloff' triangle (1903) refer to Fagerberg (1956).
On the tibia, in the intercondylar area (Fig. 3), the medial tubercle anteriorly raises its contour above the level of the joint surface (at point A) earlier than the lateral tubercle and proceeds, in an even slope, to its peak whence it falls posteri-
orly rather abruptly towards the posterior intercondylar fossa. The medial tubercie, in most cases the taller one (Mouchet and Noureddine, 1925; Schlüter and Becker, 1955; Jonasch, 1958) is thus discernible by having only one peak, shaped as an even curve and an abrupt fall posteriorly. The lateral tubercle starts behind the medial tubercle, rising to a pronounced anterior peak, but thereafter proceeds in an
even curve, often after a small notch, posteriorly until reaching the posterior contour of the lateral tibial condyle. Anatomically this junction of the lateral tubercle and lateral condyle is at the postero-medial corner of the socket of the lateral tibial condyle (Jacobsen, 1974). Thus, the lateral tubercle has two curves or peaks. In some cases there is still, just anterior or posterior to the
posterior contour of the medial tubercie a faint contour representing the posterior wall of the intertubercular crest. Present investigations: The most characteristic landmark of the tubercles, the posterior arch of the lateral tubercle, is visualized most clearly in increasing external rotation. At a 30° to 450 external rotation this arch is still clearly visible, but now the posterior contour of the lateral tibial condyle is made up by a more laterally situated part of the posterior
surface of the condyle, so that now it is not possible to observe the direct course of the posterior arch of the lateral tubercle onwards in the posterior condylar contour (Fig. 4). At 5°-10° internal rotation the posterior arch of the lateral
tubercle is superimposed on the posterior contour of the
medial tubercle, and at 15°-30° internal rotation it
is
position in relation to the central beam, the "roof" of the
visible in front of it.
intercondylar femoral fossa being curved in several directions,
The crest of the anterior intercondylar area, described by
so that different parts of this curved roof will be hit tangentially by the rays, depending upon the position of rotation of the knee joint. Thus, the angle between Blumensaat's line and the axis of the femoral shaft is least around the neutral
Negru, forms a contour on the radiograph. It may be discerned in the neutral position, but grows more distinct on internal
rotation. At 30° and 45° internal rotation and from 30° of external rotation it is hidden by the condyles.
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menisci are situated in these sulci (on all specimens) in agreement with Fick (1904). The joint surfaces of the tibial condyles and
402
Fortscht. Röntgenstr. 125, S
K. Jacobsen Figs. Sa and b. Radiograph of the same specimen in 15° external rotation (Sa) and 45° external rotation (Sb). Medial tibial condyle with the long lead strip most distally, both on the anterior and posterior
aspect. Lateral tibial condyle with a shorter strip. The sketches show the relation of the fibular head to the condyles of the tibia: unbroken lines: fibula and lateral condyle and tubercie. Broken lines: medial condyle and tubercle. Note that in 5 a the capitulum
flbulae may be mistaken to articulate with the big, squared (medial) condyle - and that this mistake is unmasked in 5 b. Note also the course of the posterior arch of the lateral and
Fig. 5a
Fig. Sa2
Fig. Sb1
At the middle of the anterior intercondylar area on the lateral
radiograph Parsons' knob is in some cases delineated as a triangular contour. On a specimen the anterior edge of the soft-tissue shadow of the anterior cruciate ligament may be
Present investigations: By marking, it can be demonstrated that the proximal limit of the insertion area on the lateral radiograph (in neutral position) corresponds to the point of intersection between the sharp contour of this area and the contour of the articular socket of the medial tibial condyle. The bone contours of the lateral condyle are either entirely
traced to its insertion on this peak. The prominence is present on the radiographs of 4 out of the 14 specimens (also on Fig. 3). Parsons' knob is thus identical with the linear or most often slightly convex, in a few slightly concave. prominence described by Politzer & Pick (1937) known in radiological literature as the "tuberculum intercondylare tertium".
The bone contour of the medial condyle is always concave.
The posterior intercondylar area gives a sharp contour
anterior part of the more oblique medial articular surface is situated above the level of the lateral one. However, this appearance is very apt to get distorted on tilting of the bone in the frontal plane in relation to the central beam.
which may be found by tracing the posterior contour of the medial tubercie downwards and backwards, where it dips down between the two tibial condyles (Fig. 3). This area being equal to the insertion facet of the posterior cruciate ligament which is distinctly defined on a macerated specimen of the bone (Jacobsen 1974).
The bone contour of the lateral articular surface is more high-seated in the majority of cases. Only the very most
Present investigations: Anteriorly, the contour of the crest of the anterior intercondylar area (Negru) is of a varying situa-
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medial tubercle.
Landmarks of the knee joint on the lateral Radiograph during rotation
The posterior contour of the lateral tibial condyle may be found by tracing the posterior convex, curved part of the
403
ward. In cases of severe abnormalities, however, a greater rotation is possible. Therefore, the present study of the kneejoint landmarks during rotation has been necessary. The contours of the femoral condyles, especially the limiting grooves, were studied by Ravelli - but without investigation
lateral tubercle. Then it may be traced forwards in the convex line of the socket contour. However, the lateral tibial condyle may form 2 or 3 densely placed, more or less sharply delimited contours (two on Fig. 3). The posterior contour of the medial
of the influence of rotation. His findings are confirmed by the present author. I also share Ravelli's opinion that the shadow
tibial contour is found, in the neutral position, behind the
so seldom present (in 10% of Ravelli's cases and in 13% of Falk's [1963]). Moreover, it may be confused with an ossification centre in the medial head of the gastrocnemius muscle which is a very uncommon occurrence (Kremser, 1930; Freyer, 1960). The adductor tubercie is also of limited value,
contour of the lateral condyle. The proximal, posterior point, B on Figure 3, represents the point of intersection of the two contours of the medial joint socket. The medial tibial condyle is large and squared-off, whereas the contour of the lateral condyle is more slender.
Present investigations: On rotation of the specimen this characteristic condylar shape remains unchanged. On medial rotation it grows ever more distinct that the head of the fibula is not in contact with the squared-off contour. From 5° to 30°
external rotation the appearances may give the erroneous impression that the head of the fibula articulates with the large squared-off condylar contour. It is not until at 45° external rotation that it is disclosed that articulation takes place with the more pointed contour which is thereby unmasked as the lateral condylar contour (Fig. S). Thus, the head of the fibula is a poor landmark for determining the condylar contours (especially from 5°-30° external rotation which is common on clinical lateral radiographs). The insertions of the soft tissues in the intercondylar tibial areas may be determined on the lateral radiograph: Where Parsons' knob or tubercle is present the insertion of the anterior cruciate ligament is from the top of this knob and down its posterior surface, further backwards to the top of the medial tubercie. The anterior horn of the medial meniscus
inserts on the anterior, declining surface of Parsons' knob. If the latter is not present, the anterior horn of the meniscus inserts in the area between the crest of the anterior intercondylar area and the anterior superior edge of the medial articular socket. This slightly excavated facet Negru called
the "impressio digitalis tibiae". Just posterior to it the insertion of the ligament starts. The demarcation of the insertion facet for the posterior cruciate ligament, has been described above. The posterior horn of the medial meniscus inserts on a small facet on the posterior declining contour of the medial tubercle proximally to the contour of the medial articular socket. The posterior horn of the lateral meniscus inserts on the top of the intertubercular crest. The insertion
of the anterior horn of the lateral meniscus can not be accurately localized, but the facet is just anterior to the beginning of the lateral tubercle anteriorly. The anterior limit of the origin of the posterior cruciate ligament from the intercondylar femoral fossa is localized at the anterior point of Blumensaat's line. The posterior limit of the origin of the
anterior cruciate ligament from the intercondylar femoral fossa is found at the posterior angulation of Blumensaat's line.
Discussion With the gonylaxometer - an apparatus for radiological measurement of the drawer sign by hydraulic action on the knee joint (Jacobsen, 1976) - the first exposure (unloaded, 90° flexed knee) is made in a position very close to what is defined here as "neutral" or "zero" position. Rotation of the tibia during traction and pressure amounts in the predominant majority of cases to less than about 15° inward or out-
of the fabella, situated in the lateral head of the gastrocnemius muscle, is of limited value as a landmark, because it is
as it is rarely distinguishable from muscle traces at the
insertion of the medial and lateral heads of the gastrocnemius muscle (Lachmann 1937).
Teichert (1955) has described yet another means of determining the side of the femoral condyles on the lateral radiograph : In the lateral part of the femoro-patellar joint the femoral and patellar contours proceed for a longer distance parallel than in the medial part of this joint. This sign is pronounced in "intermediate flexion". In studies at 90° flexion it may lead to errors. The femoral condyles are easy identified - also on Teichert's figures - by the situation of the limiting groove. Kennedy & Fowler (1971), who used lateral radiographs for
measuring anterior instability in the knee joint, do not mention the groove on the medial femoral condyle, where it may be just as pronounced, or more so, than on the lateral.
Nor do they mention the situation of the grooves on the articular surfaces. The conclusion is that reliable landmarks for identifying the
femoral condyles on the lateral radiograph are: The lateral femoral condyle has a far larger guiding ridge for the patella than the medial condyle. On the lateral femoral condyle the limiting groove is situated at about the middle of the articular surface, but on the medial condyle within its anterior, proximal third. According to Kennedy & Fowler the lateral tibial condyle "is identified by its more squared-off posterior projection". On their Figure 20 and its legend they thus misinterpret the posterior contour of the medial tibial condyle as that of the lateral. The results of their measurements are questionable, as these landmarks were used in measuring the drawer sign in the knee joint.
It may be concluded that the following landmarks are applicable for identifying the tibial condyles: The lateral intercondylar tubercie proceeds backwards from its peak in an even, convex arch continuing direct in the posterior contour of the lateral tibial condyle. The medial tubercle slopes from its peak rather steeply downward and backward in a straight or concave line towards the posterior intercondylar area.
The proximal, posterior corner of the medial tibial condyle is formed by the meeting of the two arcuate contours
of the outer and inner demarcation of the articular socket. The posterior contour of the lateral tibial condyle is more pointed and more slender than the large squared-off contour of the medial condyle. On more than 900 lateral radiographs exposed in the gonylaxometer there has never been a lack of these landmarks in sufficient numbers for identification of the condyles. A description of the relation of the ligamentous and menis-
ceal insertions to the contours on the lateral radiograph
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tiOn: below the levels of both joint surfaces, between them or above both. The latter is very uncommon (seen in only one out of the 14 specimens).
Fortschr. Röntgenstr. 125, 5
M. Friedrich u. Mitarb.
Fortschr. Röntgenstr. 125, 5
is of particular importance in cases of abnormalities where
im lateralen und medialen Gastrocne-
avulsions of bone may be found in the sites concerned.
mius-Kopf. Röntgenpraxis 2 (1930) 134
Moreover, it may be of importance in interpreting an arthrography with reference to cruciate ligament damage.
Lachmann, E.: The roentgen anatomy
of the knee joint. An experimental
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