| Summary: | The evolution of humans to an upright stance has led to a change in the postural relationship between the human pelvis and the lower limb. However, despite the uncovering of the femoral head anteriorly, the bipedal hip remains inherently stable due to its bony anatomy and strong ligamentous support. Deviation from normal osseous anatomy results in a loss of constraint to dynamic movement with pathological translation of the femoral head (1,2). A similar scenario is expected with compromise of the surrounding soft tissue structures. A presentation of nine clinical cases describes the condition thought to result from compromise of the anterior hip ligaments. A triad of clinical signs are described. To investigate the patho-mechanical mechanism in these patients, a magnetic resonance imaging (MR.I) study of symptomatic hips was performed. Although increased joint , translation was not demonstrated in this study, distinctive appearances of the iliofemoral ligament were identified. Results of a cadaveric study then go on to demonstrate the stabilizing roles of the anterior capsular ligaments. With damage to the anterior capsule, increased translation of the femoral head was seen not only throughout movement range, but specifically correlated with the functional positions of the iliofemoral and pubofemoral ligaments. The concept of instability of the hip due to soft tissue laxity is postulated to result in progressive damage to the labrum and chondral surfaces as the femur abuts the acetabular rim during extra-physiological motion. Chronic capsular injury may destabilise previously asymptomatic hips with subsequent development of pain in young, active patients. Knowledge of the function of the capsule and its reinforcements is critical if hip surgeons are to manage these patients appropriately and understand the implications of capsular compromise on long-term function.
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