The Role of Anterior Capsular Laxity in Hip Microinstability: A Novel Biomechanical Model:

Background:Hip microinstability is an increasingly recognized source of hip pain and disability. Although the clinical entity has been well described, the pathomechanics of this disease remain poorly understood.Purpose/Hypothesis:The purpose of this study was to determine the role of capsular laxity in atraumatic hip microinstability. Our hypothesis was that cyclic stretching of the anterior hip capsule would result in increased hip range of motion and femoral head displacement.Study Design:Controlled laboratory study.Methods:In this study, 7 hip specimens met inclusion criteria (age, 18-46 years). Specimens were stripped of all soft tissue, aligned, cut, and potted by use of a custom jig. A materials testing system was used to cyclically stretch the anterior hip capsule in extension and external rotation while rotating about the mechanical axis of the hip. A motion tracking system was used to record hip rotation and displacement of the femoral head relative to the acetabulum in the anterior-posterior, me...