FEATURE: HIP RELATED PAIN HIP-RELATED PAIN & FEMOROACETABULAR IMPINGEMENT SYNDROME flexion range. The review indicates in hip joint pathology is inconsistent.41 FAI syndrome, although further studies that further information on more sport Alterations in muscle composition, such with larger sample sizes are required specific activities such as running is need as increased fatty infiltration, may to confirm these findings. ed, to determine if these tasks present a contribute to variations in the relationship problem for those with FAI syndrome. between size and strength.42 Fatty Most studies examining size and fatty infiltration has been reported in joint infiltration in hip pathology are focused PART THREE: HOW DOES pathology to occupy space within healthy on hip osteoarthritis (OA). Decreases in HIP-RELATED PAIN AFFECT muscle tissue and decrease its potential size of muscles around the hip as well as MUSCLE FUNCTION? WITH contractile force in relation to its overallincreases in fatty infiltration have been PETER LAWRENSON size.43To ascertain whether changes in demonstrated in end stage hip OA across size and composition are evident in FAI a number of studies,46-48yet magnitude Strength deficits are a common clinical syndrome and other hip pathology, a of these changes may vary based on the feature in FAI syndrome,36 37and other review of the literature was undertaken. specific muscle investigated and stage articular hip pathology, yet our of pathology.42 understanding of the mechanism behind Two studies were identified that looked these deficits is lacking. Interventions at muscle size and composition in FAI There are few studies with large sample designed to address strength deficits in syndrome, compared to dysplasia and sizes, investigating muscle size and hip pathology are scarce and have mixed healthy controls. Iliocapsularis, a muscle composition in intra-articular pathology. results.38-40In order to ensure future proposed to play a role in active stability With the limited evidence seen FAI interventions are appropriately targeted of the hip joint, was found to have a syndrome, and what was observed in OA, an improved understanding of the smaller size and greater fatty infiltration there are some indications of changes in mechanisms underlying deficits in in people with FAI syndrome.44 In size and composition of muscles across strength is required. contrast, rectus femoris, was shown to the spectrum of pathology that require have a significantly greater size.45These further investigation. Cam FAI syndrome Decreases in muscle size have been findings indicate there may be alterations and other intra-articular pathology have correlated to deficits in strength, in structure of the deep muscles been linked to the pathogenesis of hip although the nature of this relationship surrounding the joint in populations with OA49 50and thus, additional research to ascertain any commonalities between these groups is warranted. This may not only to improve our understanding of intra-articular pathology, but to also identify potential factors that may that play a role in disease progression. SUMMARY Hip-related pain, including FAI syndrome, frequently affects active and sporting populations, yet we have limited understanding of its aetiology and interventions that can be employed to ameliorate symptoms. These systematic reviews indicate that people with hip- related pain are likely to demonstrate intra-articular pathology (/home/webapps/asp_au/data/asp/publications/au-sports-medecine-australia/publications/sport-health-volume-36-april-2018/sport-health-volume-36-april-issue60% may have labral or cartilage lesions), but the clinical relevance of these lesions are not known. They are also likely to exhibit small to moderate differences in movement patterns (e.g. less hip extension, internal Fig3: T3 MRI slice at the level of the femoral head, demonstrating muscle CSA. A, rotation) and smaller deep hip muscles. acetabulum; F, femoral neurovascular bundle; FH, femoral head; GMa, Gluteus maximus; Combined with previous studies GMe, Gluteus medius; GMi, Gluteus minimus; IC, Iliocapsularis; IL, Iliacus; P, Psoas major;identifying lower hip muscle strength,51 RF, rectus femoris; S, Sartorius; and TFL, tensor fascia lata. 40 VOLUME 36 • APRIL ISSUE 2018