HIP INSTABILITY

The depth and conformity of the articulation between the femoral head and acetabulum provides a great deal of intrinsic stability to the hip joint. Despite this, hip instability does occur and can be debilitating. There is evidence to support traumatic and atraumatic capsular laxity as a source of hip pain and persistent disability. ^1-3 Traumatic hip instability can result from high-energy trauma, like that seen in motor vehicle accidents. It can also result from low-energy injuries seen in athletic competition. ^{4, 5} Proposed causes of atraumatic capsular laxity include generalized ligamentous laxity, collagen disorders like Ehlers-Danlos, and microtrauma from repetitive activities that force the hip into external rotation as seen in golfers, gymnasts, dancers, or throwers. ^1-3 Dynamic and transient incongruency can lead to abnormal joint forces which may result in capsular and labral injuries, capsular redundancy, and femoral neck impingement at high flexion angles (secondary impingement). Although diagnosing hip instability can be challenging, identifying the cause of hip instability is important because it can help guide the surgeon toward the most appropriate treatment. The appropriate diagnosis relies upon a combination of clinical suspicion, physical examination, and radiographic findings.