IJSPT

INVITED CLINICAL COMMENTARY

GAIT CONSIDERATIONS IN PATIENTS WITH FEMOROACETABULAR IMPINGEMENT Dirk Kokmeyer, PT, DPT, SCS, COMT1,2 Melissa Strzelinski, PT, MPT1,2,3 Bryan J. Lehecka, PT, DPT2,4

ABSTRACT The literature describing the characteristic features of femoroacetabular impingement (FAI) has been on the rise, increasing awareness of this pathology in the young, active population. The physical therapist should consider FAI as a contributing factor to anterior hip pain, impairments, and functional deficits of the lower quarter. The dynamic interplay of anatomical variations, pain, and muscle function and their effects on gait in patients with FAI, however, is poorly understood. Small sample populations and variability in radiological, demographic, and clinical presentations in those with FAI have precluded meaningful insight into gait analysis and FAI, reiterating the need for further research in this domain. The purpose of this clinical commentary is to review the literature that defines normal gait at the hip joint and abnormal gait as a result of FAI and labral pathology or surgery aimed at correcting it. Secondarily, the authors aim to offer clinicians a strategy to progress the post-surgical patient to normal, unassisted gait while reducing the risk for anterior hip pain. Lastly, the authors of this commentary aim to identify specific areas for future research directed at therapeutic interventions in patients with FAI and those who have undergone surgery to correct it. Key Words: Anterior hip pain, biomechanics, femoroacetabular impingement, gait, gait analysis Level of Evidence: 5

1

Howard Head Sports Medicine, Vail, Colorado, USA 2 Rocky Mountain University of Health Professionals, Provo, Utah, USA 3 Athletico Physical Therapy, Chicago, Illinois, USA 4 Wichita State University, Wichita, Kansas, USA Acknowledgement: The authors would like to thank Kimberly Lyons-Mitchell of the Vail Valley Medical Center for her assistance.

CORRESPONDING AUTHOR Dirk Kokmeyer Howard Head Sports Medicine, 181 West Meadow Dr. Vail, CO 81657 Phone: (970)476-1225 Email:[email protected]

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INTRODUCTION Hip arthroscopy presents several challenges to the physical therapist and patient. The primary goal of this type of surgery and both conservative or post-surgical physical therapy for the treatment of femoroacetabular impingement (FAI) and labral pathology is to reduce anterior joint forces that place the labrum at risk for injury.1-4 Several authors have outlined hip arthroscopy rehabilitation guidelines that mesh the best available evidence with clinical experience.2,5-12 Collectively these authors agree that restoration of normal gait may be the most critical aspect of rehabilitation. Although surgery to correct FAI restores normal gait kinematics one year post-operatively,13 patients are likely to experience increased anterior hip pain with the initial progression to walking without an assistive device. This pain is commonly described as hip flexor tendonitis. 6,12 Several authors and clinicians have observed decreased gluteal recruitment in hip extension following hip arthroscopy. This altered function influences gait as a deficient hip strategy at toe off, when the hip is maximally extended. Gluteal muscle activity has been observed to decrease with increased joint effusion, suggesting a plausible explanation for insufficient gluteal function.14 Furthermore, recent 3-D biomechanical modeling studies have helped rehabilitation professionals understand how irregular muscle forces contribute to anterior hip joint loading. In a musculoskeletal model of the hip that estimated hip joint forces based on the moment arms of 43 muscle units Lewis et al15,16 discovered that increasing joint angles of active flexion and extension combined with decreased muscle activity of the iliopsoas and gluteal muscles increase anteriorly directed forces at the hip joint. Therefore, decreased gluteal activity secondary to hip arthroscopy may explain the genesis of anterior hip pain. The purpose of this clinical commentary is to review the literature that defines normal gait at the hip joint and abnormal gait as a result of FAI and labral pathology or surgery aimed at correcting it. Secondarily, the authors aim to offer clinicians a strategy to progress the post-surgical patient to normal, unassisted gait while reducing the risk for anterior hip pain. Lastly, the authors of this commentary aim to identify specific areas for future research directed at

therapeutic interventions in patients with FAI and those who have undergone surgery to correct it. NORMAL GAIT KINEMATICS AND MUSCLE ACTIVITY In order to understand gait deviations commonly observed in individuals with FAI, one must first grasp normal hip gait kinematics and muscle activity. A normal gait cycle is defined as “the interval between two successive occurrences of one of the repetitive events of walking.”17 This is generally described as the time of heel contact of one foot to heel contact of the same foot. The gait cycle is broken down into eight periods occurring in two phases: initial contact, loading response, mid-stance, terminal-stance, pre-swing, initial swing, mid swing and terminal swing. The stance phase accounts for 60% of one gait cycle and includes initial contact, loading response, mid-stance, and terminal-stance. The swing phase accounts for 40% and includes pre-swing, initial swing, mid swing and terminal swing. Percentages of the gait cycle are described beginning at initial (or heel) contact (0%) to the end of terminal stance, (or toe-off, 50%), to the following heel contact (100%).17 The largest arc of hip motion occurs in the sagittal plane with brief muscular demands, while the smallest arc of motion, occurring in the frontal plane, requires considerably greater muscle activity.18 (Figure 1) During initial contact, the hip reaches a peak flexion angle of about 20-30⬚.18,19 Initial contact is brief, comprising only 0-2% of the gait cycle. Loading response continues up until 12% of the gait cycle. Initial contact exposes the hip to an unstable position because of the immediate increase in body weight through the limb, which halts forward advancement of the limb as the trunk continues to advance forward.18 In the frontal and transverse planes, the hip is in a neutral position relative to the pelvis.18 The hamstring muscles eccentrically contract to decelerate the knee and prevent hyperextension. Then the semitendinosus and semimembranosus assist the lower gluteus maximus and adductor magnus in extending the hip through loading response.17,18 Additionally, the upper portion of the gluteus maximus and the gluteus medius reach peak activity, and the posterior tensor fascia latae (TFL) reaches moderate activity in order to stabilize the hip in the frontal plane and eccentrically control adduction and

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Figure 1. Graphic representation of the gait cycle. (Adapted from Perry J, Burnfield JM. Hip. Gait Analysis: Normal and Pathological Function. 2nd ed. Thorofare, NJ: SLACK; 2010:103-127.)

internal rotation of the femur.18,20 Approximately 10⬚ of adduction occurs as the hip is loaded.18 Near the end of loading response (10% of the gait cycle), an increase in knee flexion decreases the hip extensor moment, diminishing the activity of the lower gluteus maximus, adductor magnus and biceps femoris cease.18 The great toe of the opposite lower extremity leaves the ground when the weight bearing hip reaches approximately 25⬚ of flexion marking the end of double limb support and loading response.17 Mid-stance occurs as the opposite great toe leaves the ground and the stance heel rises from the ground at approximately 12-31% of the gait cycle.17,18 Early in the mid-stance phase, the semitendinosus and semimembranosis remain active to augment hip extension as inertia and gravity continue to extend the hip past the neutral position (27% of gait cycle).17,18 Frontal plane muscle activity appears dominant in this phase.17 The gluteus medius and upper gluteus maximus reach peak activity during mid-stance to stabilize the pelvis and return it to a neutral position.18,21 Gluteal activity then diminishes prior to terminal stance as the posterior fibers of the TFL remain active. Heel rise occurs at approximately 32% of the normal gait cycle, and ends mid-stance.17 Terminal stance occurs at approximately 31-50% of the gait cycle.18 This begins as body weight rolls over the forefoot causing the heel to rise from the ground.18 The hip continues to extend to approximately 20⬚ of extension through a combination of hip extension, anterior pelvic tilt and backward rotation of the pelvis, which has been described as apparent

hyperextension.18,22 The anterior portions of the TFL and adductor longus serve as active restraints to control end-range hip extension, while the iliofemoral ligament acts as a passive restraint.1,18 The TFL also provides a small abduction force for frontal plane stability. Adductor longus activity begins at 46% of gait cycle and peaks at approximately 50% of the gait cycle. It initiates hip flexion as the hip transitions from extension to flexion. Peak acetabular pressure (throughout the acetabulum) has been observed during terminal stance.21 Coincidentally, the iliopsoas generates substantial force during late stance, yet does not contribute to closed kinetic chain support, lending to the theory that the primary function of the iliopsoas during gait is swing initiation.23 Opposite heel contact marks the beginning of preswing, which comprises 50-62% of the gait cycle.17,18 The femur advances as the foot rolls forward on the forefoot rocker. The gracilis and rectus femoris assist the adductor longus in flexing the hip prior to toe-off, which occurs at 60% of the gait cycle and represents the end of the stance phase.17,18 While the rectus femoris assists in flexing the hip and controlling knee extension, its activity is brief, and at times negligible.18 In the frontal plane, the gracilis and adductor longus decelerate hip abduction as body weight shifts to the contralateral limb.18 The sartorius responds with an external rotation and abduction moment in order to counteract the adductor muscles’ forces.18 As the toe leaves the ground, initial swing begins, which constitutes 62-75% of the gait cycle.17,18 The propulsive action of the ankle during pre-swing

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flexes the hip nearly 20⬚ within 0.1 seconds.18 The gracilis, iliacus, psoas, adductor longus, and sartorius augment this motion and cease activity prior to mid-swing, when the tibia is vertical to the ground.17,18 The gracilis muscle is an exception as it remains active until the loading response of the next gait cycle.18 The flexion moment from the hip swings the tibia like a pendulum past the leg of the opposite limb, marking the beginning of mid-swing (75-87% of gait cycle).17,18 During this phase, the hip passively flexes an additional 10⬚, while the semimembranosus and long head of the biceps femoris initiate eccentric control of the tibia.18 The iliopsoas continues to flex the hip until the tibia is vertical to the ground, at approximately 86% of the gait cycle. The hip then ceases to flex as the knee continues to extend like a pendulum, leading to heel (initial) contact and the end of the gait cycle. Surprisingly, prior to heel contact , contact pressures at superior hip joint have been observed to peak, indicating muscle activity in an open kinetic chain is capable of generating substantial joint forces.21 FAI AND GAIT Several authors have reported biomechanical gait characteristics of individuals with FAI24,25 and following corrective surgery for FAI.13,26,27 In a kinematic and kinetic evaluation of individuals with FAI, Kennedy et al25 reported a significantly decreased peak hip abduction angle at the beginning and throughout the swing phase, which contributed to a decrease in total frontal plane range of motion as compared to controls. Additionally, a marginally significant (p=0.047) decrease in peak hip extension angle at the end of the stance phase was observed. In a larger, controlled sample, Hunt et al24 reported decreased peak extension, adduction and internal rotation angles in subjects with FAI. Few studies have evaluated pre-and post-operative gait mechanics in individuals with FAI. Rylander et al13,27 performed two studies evaluating pre- and postoperative gait mechanics in individuals with FAI. In the first study,13 decreased hip flexion in the sagittal plane was observed in patients with FAI, who were scheduled for hip arthroscopy. One year following surgery, sagittal plane flexion and gait kinematics returned to normal. However, the second study27

did not show an improvement in frontal plane ROM. Furthermore, a second analysis of stair climbing demonstrated no change in sagittal plane ROM one year after surgery and a significant difference in sagittal plane ROM when compared to matched controls. Moreover, pelvic transverse plane ROM and anterior tilt was significantly greater than controls. These results suggest that hip arthroscopy significantly improves normal gait one year after surgery, yet frontal plane ROM remains questionable. More demanding activities that require increased muscle activity and greater ranges of motion do not return to normal, when post op patients are compared to healthy controls. Other evidence suggests that surgical procedures may negatively impact gait mechanics. Brisson et al26 reported decreased sagittal plane motion of the hip in patients who underwent an open or combined open and arthroscopic procedures, compared to age, gender and BMI matched controls, at a mean followup time of 21.1±9.4 months. Of note, the open procedure required incision of the iliotibial band and splitting of gluteus maximus, and the combined procedure occasionally required rectus femoris release. The different approaches may explain some of the observed biomechanical differences. Additionally, follow-up times in this study were based on convenience and not routinely scheduled follow-up times (range 10-32 months), which may have influenced results. Rylander reported that pincer type impingement was more restrictive to hip internal rotation than cam impingement.26 MUSCLE BALANCE/FUNCTION OF THE HIP Precursory knowledge of the hip’s extensive muscular network is critical to developing effective strategies for rehabilitation of gait in the presence of FAI. During normal gait, muscles account for the majority of support that counteracts ground reaction forces that occur during stance.23 Twenty-three muscles cross the hip joint, including the rarely mentioned iliocapsularis, each with unique functions.28,29 (Table 1) In addition to their primary actions; most muscles of the hip also have a secondary action. Moreover, the actions of the hip muscles hinge largely on the position of the hip at the time of the muscular contraction.30 For example, in addition to adduction, the adductor longus has the potential to extend the

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Table 1. Muscles crossing the hip joint and their primary functions Hip Muscle Adductor brevis Adductor longus Adductor magnus Biceps femoris (long head) Gemellus inferior Gemellus superior Gluteus maximus Gluteus medius Gluteus minimus Gracilis I li ac u s Iliocapsularis Obturator externus Obturator internus Pectineus Piriformis Psoas major Quadratus femoris Rectus femoris Sartorius Semimembranosus Semitendinosus Tensor fasciae latae

Primary Muscle Function(s) at the Hip Adduction Adduction, lexion Adduction, extension Extension External rotation External rotation Extension, external rotation Abduction Abduction Adduction F le x io n Tightens the hip capsule External rotation, adduction External rotation Adduction External rotation Flexion External rotation Flexion Flexion Extension Extension Abduction, lexion

hip at 90⬚ of hip flexion and the ability to flex the hip at 0⬚ of hip flexion. The hip extensor muscles as a group have the potential to create the greatest torque across the hip, followed by the flexors, adductors, abductors, internal rotators, and then external rotators.29 The relatively massive bulk of the gluteus maximus and adductor magnus, which have been shown to comprise about 23% and 18% of the entire mass of hip muscles, respectively, likely account for this force potential.31 Hip muscle imbalances and weaknesses have been correlated with multiple pathologies. In a study of females with patellofemoral pain (PFP), the hip adductor/abductor isometric strength ratio was 23% higher in the PFP group compared to controls.32 The ratio of anteriomedial hip strength (adductor, internal rotator, and flexor musculature) to posterolateral hip strength (abductor, external rotator, and extensor musculature) was also 8% higher in the PFP group.

In another study of females with PFP, individuals in the PFP group demonstrated significantly less hip torque production compared to the control group (14% and 17% less hip abductor and hip extensor strength, respectively).33 Impaired muscle function has been identified in patients with iliotibial band syndrome, hip osteoarthritis, labral tears of the hip, previous hip surgery, and other hip pathology.34-38 The theoretical relationship between gluteal weakness and FAI is especially relevant to the topic of hip arthroscopy. In a study of hip bony architecture, increased anteversion angles, specifically those greater than 15⬚, were correlated with larger and more frequent anterior labral tears.39 The compensatory femoral internal rotation associated with large alpha angles can be seen as analogous to the internal rotation associated with gluteal weakness. Attention to training the gluteal muscles following hip arthroscopy is warranted to control internal rotation moments that occur at the femur in order to reduce potentially injurious forces to the anterior labrum. IMPORTANCE AND FUNCTION OF GLUTEAL MUSCLES IN GAIT Gluteal muscle function has significant implications for lower extremity pathology, likely due to its relevance to walking and running. Although the gluteus maximus controls flexion of the trunk during upright posture and walking, and restrains femoral internal rotation, its major role is to extend the stance side hip and control flexion of the trunk during running. Electromyographic (EMG) study of the muscle has shown that it is considerably more active during running than walking, at which time it is largely quiescent.40 Studies evaluating the relationship between the gluteus maximus and ambulation have yielded mixed results. One study reported increased gluteus maximus EMG activity with increasing speeds of gait, while another reported increased gluteus maximus activity with both faster and slower gait speeds than participants’ self-selected pace, and yet a third study found no significant changes in gluteus maximus EMG activity at different walking speeds.41-43 Gluteus medius function may be more significant during ambulation than its larger gluteal counterpart. It has been reported to provide frontal plane pelvic stability during early stance phase and prevent

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the contralateral pelvis from dropping.43 Moreover, its activity is extended (although not increased) at higher speeds, providing pelvic stability during late swing phase, and assisting in foot clearance during late stance phase.44 Future attention to understanding the influence of gluteal activity during walking is warranted; as such findings may delineate the relative focus on strength training, versus endurance, or neuromuscular retraining in post-operative hip rehabilitation. Multiple retrospective and prospective studies have identified a significant correlation between PFP and hip strength among runners, specifically that of the gluteal muscles.33,45,46 Hip abductor weakness has been identified in runners with iliotibial band syndrome.34 Most studies of gluteal function and running mechanics or running injuries employ isometric strength testing, likely given the prevalence of manual muscle testing among clinicians. However, both hip extension and hip abduction endurance (evidenced by isotonic hip extension

endurance and side plank endurance, respectively) appear to be even stronger predictors of potentially injurious running mechanics, specifically hip internal rotation.33,47,48 Extrapolating these predictors to community (or prolonged) ambulation, examination of gluteal muscle endurance should be considered; as such measures could prove beneficial in understanding the compensatory gait mechanisms observed following hip arthroscopy. The gluteal endurance measures (GEMs) described in this clinical commentary may yield insight during examination distinct from manual muscle testing or shorter-duration functional testing. (Table 2) Gluteus medius endurance may be most important early in the rehabilitation process, such as during the transition to unassisted ambulation, given its aforementioned role during the stance phase of gait. Gluteus maximus endurance, on the other hand, may be more important in later stages of rehabilitation as the patient wishes to increase gait speed or navigate inclined ground.

Table 2. Gluteal endurance measures (GEMs) 1. Endurance Abduction (Figure 2) Positioning: The patient is sidelying with the hip and knees in 0° of lexion, feet together with toes facing forward, arms relaxed, and trunk in a neutral position. A wall may be used behind the patient to aid maintenance of the position and test motion. Testing: The patient is instructed to abduct the upper hip (test hip) from the testing surface to achieve 30° of hip abduction as measured and monitored by the tester. The tester measures the distance of the raised lateral knee to the testing surface and uses a hand hold in space next to the measured distance on a ruler as a reference point for the patient to contact with his/her lateral knee during each abduction repetition. A metronome or timer is used, and the patient is instructed to repetitively abduct then lower the hip to the pace of one second per movement (i.e. one second up, one second down) without rest between the motions. The tester is allowed to give cues to the patient during testing to re-match the beat of the timer or re-achieve correct positioning, although no motivational cues are given. If the patient fatigues and is no longer able to contact the tester’s hand, match the beat of the timer, or maintain proper positioning, the test ends. The test duration is recorded in seconds. 2. Endurance Bridging (Figure 3) Positioning: The patient is hooklying with his/her hips lexed to 60°, feet lat, and hands folded over the chest. Testing: The patient is instructed to lex the hip of the non-test leg to 90° with the rest of the limb relaxed and foot off the ground, and maintain the femur in a vertical position throughout the test. The patient is then instructed to press through the heel to extend the test hip to 0° of lexion as measured and monitored by the tester. The tester measures the distance of the anterior superior iliac spine (ASIS) to the testing surface and uses a hand hold in space next to the measured distance on a ruler as a reference point for the patient to contact with his/her ASIS during each bridge repetition. A metronome or timer is used, and the patient is instructed to repetitively raise and lower the hip to the pace of one second per movement (i.e. one second up, one second down) without rest between the motions. The tester is allowed to give cues to the patient during testing to re-match the beat of the timer or re-achieve correct positioning, although no motivational cues are given. If the patient fatigues or is no longer able to contact the tester’s hand, match the beat of the timer, or maintain proper positioning, the test ends. The test duration is recorded in seconds.

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DISTAL CONTRIBUTIONS TO GAIT MECHANICS Though significant relationships between both proximal and distance factors in patellofemoral pain syndrome have been identified, comparable evidence in the hip is elusive. Poor hip abduction strength has been associated with increased femoral internal rotation and adduction moments in running, and led to increased focus on proximal strengthening as a preventative strategy for knee pain.33,34,46,47 Heiderscheit et al49 described the utility of increasing cadence, while decreasing overall knee ROM excursion as a strategy for decreasing anterior knee pain in runners. Moving distally, numerous studies have addressed the influence of distal foot mechanics on knee pain; however, the literature lacks consensus regarding the impact of subtalar motion on proximal structures, particularly the low back and pelvis.50 Duval et al50 evaluated varying degrees of calcaneal inversion and eversion, and toe internal and external rotation on low back and pelvic mechanics. A moderate correlation between subtalar pronation and increased internal knee and hip rotation, and subtalar supination and external knee and hip rotation were reported respectively. Internal thigh rotation resulted in increased anterior pelvic tilt to a greater degree than external rotation of the thigh, causing posterior tilt. The authors of this commentary suggest that subjects did not attain end range lower leg motion in external rotation as a plausible explanation for these findings. It was hypothesized that bilateral femur internal rotation at 40⬚ pushed the femoral heads backwards against the acetabulum, and the pelvis tilted forward in response, whereas relative foot pronation had no impact on degree of pelvic tilt. Foot orthoses (FO) have been studied for their effects on a variety of lower quarter conditions. Hertel et al51 determined altering static foot position can influence proximal muscle activation, particularly the gluteus medius.51 Interestingly, a relationship between pathologies involving excessive foot pronation and effective management with FO has been correlated with gluteus medius weakness managed with a strengthening program.52 A coupling between the action of FO on foot mechanics and the hip-lum-

bopelvic complex has been suggested; however, the dynamic interaction between foot mechanics and gluteus medius function is not fully understood. Recognizing that altered gluteus medius muscle function is frequently observed in individuals with FAI highlights the need to consider distal influences on proximal hip dynamic stabilization during gait.38 Calcaneal eversion has been studied as an influence on pelvic alignment.53,54 In closed kinetic chain weight bearing, rearfoot alignment accounts for proximal joint motion. The triplanar attributes of foot pronation (calcaneal eversion, talar plantarflexion and adduction) yield tibial interal rotation, and consequent femoral internal rotation.55 Bilateral compared to unilateral calcaneal eversion yields a different magnitude of proximal influence on sagittal and frontal pelvic alignment. Pinto et al53 reported increased anterior pelvic tilt in bilateral and unilateral stance, and lateral pelvic tilt in unilateral eversion. Tateuchi et al54 took this analysis a step further, incorporating three-dimensional kinematics at the hip, pelvis and thorax in their analysis, and determined an overall impact on induced eversion in all planes, except pelvic axial rotation. These results further support consideration of foot alignment as a contributing factor to hip, pelvis, or thorax malalignment. The dynamic two-way relationship between distal and proximal joint mechanics and muscle activation suggests that alterations in foot mechanics hold promise for improving gait in individuals with FAI. The gait abnormalities associated with FAI are hypothesized to involve decreased neuromuscular control or abnormal recruitment patterns around the hip.38 The common strategy of increasing gluteus medius recruitment via hip internal rotation diminishes the activation of gluteus maximus, thereby potentially increasing anterior hip forces in the already disadvantaged FAI hip.56 In their exploration of the effect of exaggerated ankle strategies with simple verbal cueing, Lewis et al57 showed a reduction in peak hip flexion moment, power, and angular impulse, along with a lower peak hip extension moment and angular impulse. An inverse relationship between hip and ankle kinetics warrants consideration of ankle strategies as a mediating factor for the weak or painful hip to reduce hip joint forces and improve gait efficiency in FAI.

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SUGGESTIONS FOR RETURNING TO GAIT Restoring normal gait after hip arthroscopy should begin during the initial rehabilitation phase. Modalities, manual therapy, muscle pump action, cryocompression to control joint effusion and arthrogenic inhibition are critical aspects of early rehabilitation that facilitate normal return of gluteal function by the time patients are cleared to resume unassisted gait. Emphasis on gluteal activation exercises that encourage muscle recruitment at mid ranges of hip flexion and extension, where peak gluteal activity has been reported are recommended in this stage.18,21 Additionally, exercise strategies that achieve optimal gluteal activation while reducing muscle activity of the iliopsoas58 and TFL59 are encouraged. Initial limitation of hip flexor activity is advised due to the proximity of the tendon over the anterior joint. In the presence of post-operative pain and inflammation, excessive activation of the hip flexors may further increase pain and cause secondary pain inhibition. However, it should be recognized that iliopsoas strength is essential in reducing anterior hip joint forces during active flexion of the hip.60 Therefore, rehabilitation strategies that progressively strengthen this muscle group without increasing anterior hip pain should be incorporated. Without adequate iliopsoas strength, TFL dominance is likely, and potentially yields increased hip internal rotation.60,61 This necessitates prioritization of exercises that reduce TFL activity while promoting iliopsoas recruitment. While Selkowtitz et al59 identified exercises that decrease TFL activity while promoting gluteal activity, there is a pressing need to investigate which exercises best restore hip flexor activity in the post-surgical or painful hip without TFL dominance and other compensatory muscle recruitment patterns . Typically, hip arthroscopy includes some type of capsular repair, plication, or capsulorraphy in order to protect the labrum.4 Restrictions on hip external rotation and extension ROM may be advised by the orthopedic surgeon for 2-3 weeks in order to protect the healing anterior capsuloligamentous structures.2,10,12 The iliofemoral ligament resists hip extension1,62 and acts as a passive restraint for hip extension in gait,18 while the rectus femoris and hip flexor muscles act as active restraints. Hip extension is the only motion during gait where the hip nears

its end-range of motion, reported to be between 10-20⬚.17,18 Once a patient is cleared to begin unrestricted passive range of motion, careful stretching of these structures in order to restore full hip extension is indicated. Careful attention should be placed on the apparent hyperextension mechanism in order to ensure that pelvic tilting and lumbar lordosis are not substituted for hip extension during this combined motion. Weight bearing activity should begin with weight shifting exercises that promote neuromuscular control of the muscles that stabilize the hip joint. This may include side-to-side shifting to promote frontal plane pelvic stability and gluteus medius activity or forward and backward shifting in a split stance position in order to promote sagittal plane hip and pelvic stability. A novel and safe approach to place emphasis on multi-planar hip and pelvic stability and neuromuscular control is to provide manual perturbations in these positions as the patient remains stationary.2 (Figure 4) Gait training should begin with reducing loads and minimizing anteriorly driven forces of the hip joint. This can be accomplished in several ways. Aquatic therapy or the use of an unweighting treadmill are methods to reduce body weight during gait. Load may also be reduced with a single assistive device, such as a crutch or cane. Cane use has shown to reduce hip muscle activity and joint pressure by up to 40%, especially during the late stance of the gait cycle.21 Secondly, a patient may begin stepping sideways as a means of tolerating single limb support while eliminating sagittal plane motion. This may be done in a pool or on dry land. Next, reducing stride length, especially hyperextension of the knee and hip, has been reported to reduce anterior hip joint forces63 and can be easily cued during forward walking in limited or full weight bearing. Reducing gait speed and increasing ankle push-off are additional strategies that may be implemented. By cueing patients to increase ankle push-off at the terminal stance phase of gait, Lewis et al57 showed that the hip flexion moment was greatly reduced. Increased gait speed typically increases maximum hip flexion and extension of the hip.20,64 Slower gait reduces peak sagittal plane ROM, but vertical ground reaction forces, torque, and peak joint contact pressures

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Figure 4. Perturbations are applied by the therapist to the patient’s pelvis while standing with with feet staggered (a) or with a leg pressed to the wall to facilitate the hip extensors (b). This may be done with the involved limb to the front or rear. Perturbations should be applied through the pelvis and bilateral lower extremities in varying positions, intensities and speeds, based on the patient’s tolerance and ability. Table 3. Gait progression strategies 1. Reduce joint effusion 2. Maintain/restore gluteal and hip lexor recruitment in the sagittal plane 3. Restore passive hip extension 4. Improve stationary weight bearing tolerance, using weight shifting. 5. Employ strategies to reduce load and anterior hip joint forces a. Aquatic therapy b. Unweighting treadmill

pain becomes severe and resistant to interventions commonly advised in later phases of rehabilitation, patients are advised to return to crutch ambulation and passive ROM exercises until the anterior hip pain subsides. The progression of gait strategies should then be repeated until the patient returns to pain free gait.

c. Single assistive device d. Decrease stride length e. Decrease gait speed f.

Increase ankle strategy (ankle push-off)

6. Return to crutch ambulation and partial weight bearing of involved limb in those with recalcitrant anterior hip pain

are higher when compared to normal, unregulated gait speed.21 This may indicate the need to continue reduced weight bearing (use of assistive device) until full weight bearing is tolerated. (Table 3) Recalcitrant anterior hip pain occurs frequently during the rehabilitation process. The aforementioned strategies were developed in order to reduce this risk. However, in situations where anterior hip

CONCLUSION Patients who have undergone hip arthroscopy for FAI present a unique challenge for the physical therapist, given the human body’s inherent tendency to sustain efficient locomotion at the cost of abnormal kinetics and altered muscle activation. With an enhanced understanding of the alterations observed in joint and muscle function in the presence of anterior hip pain, the clinician must recognize and identify key areas of focus, starting in the immediate post-operative phase. Controlling joint effusion and early activation of gluteal musculature is critical in the eventual restoration of normalized gait.

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The clinician should progress post-operative activity, paying close attention to efficient and normal gait mechanics, and intervening immediately when compensation is noted. Significant potential remains for studying and determining the most effective means of facilitating normalized gait. This commentary provided the rationale behind the existing gait progressions the authors use, and suggests several future directions for determining optimal contributions of neuromuscular retraining, strength, flexibility, and endurance measures in the rehabilitation process. REFERENCES 1. Myers CA, Register BC, Lertwanich P, et al. Role of the Acetabular Labrum and the Iliofemoral Ligament in Hip Stability: An in Vitro Biplane Fluoroscopy Study. Am J Sports Med. 2011;39 Suppl:85S-91S. 2. Kokmeyer DJ, Hodge J. Rehabilitation of the PostOperative Hip. In: Nho S, Leunig M, Larson C, Bedi A, Kelly BT, eds. Hip Arthroscopy and Hip Joint Preservation Surgery. New York: Springer; in press. 3. Lewis CL, Sahrmann SA. Acetabular Labral Tears. Phys Ther. 2006;86(1):110-121. 4. Philippon MJ. New Frontiers in Hip Arthroscopy: The Role of Arthroscopic Hip Labral Repair and Capsulorrhaphy in the Treatment of Hip Disorders. Instructional Course Lecture, American Academy of Orthopaedic Surgeons. Chicago, IL. 2006;55: 309-316. 5. Cheatham SW, Kolber MJ. Rehabilitation after Hip Arthroplasty and Labral Repair in a High School Football Athlete. Int J Sports Phys Ther. 2012;7(2):173184. 6. Enseki KR, Martin R, Kelly BT. Rehabilitation after Arthroscopic Decompression for Femoroacetabular Impingement. Clin Sports Med. 2010;29(2):247-255, viii. 7. Enseki KR, Martin RL, Draovitch P, Kelly BT, Philippon MJ, Schenker ML. The Hip Joint: Arthroscopic Procedures and Postoperative Rehabilitation. J Orthop Sports Phys Ther. 2006;36(7):516-525. 8. Garrison JC, Osler MT, Singleton SB. Rehabilitation after Arthroscopy of an Acetabular Labral Tear. N Am J Sports Phys Ther. 2007;2(4):241-250. 9. Philippon MJ, Christensen JC, Wahoff MS. Rehabilitation after Arthroscopic Repair of IntraArticular Disorders of the Hip in a Professional Football Athlete. J Sport Rehab. 2009;18(1):118-134. 10. Philippon MJ, Goljan P, Briggs KK. FAI: From Diagnosis to Treatment. Tech Orthop. 2012;27(3):167171.

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