Microinstability of the hip: a new concept to explain unclear hip and groin pain

Background: Symptomatic hip microinstability is an increasingly recognized cause of chronic pain and functional impairment, yet it frequently remains underdiagnosed. While femoroacetabular impingement is well-documented, microinstability—defined as extraphysiologic femoral head motion—presents a distinct pathology involving osseous morphology and capsulolabral integrity.

Objective: This review aims to define the etiology of hip microinstability, establish standardized clinical and radiographic diagnostic criteria, and evaluate current conservative and surgical management strategies.

Key Points: Pathogenesis is often multifactorial, involving acetabular dysplasia, femoral maltorsion, connective tissue laxity, or iatrogenic capsular insufficiency. Clinical diagnosis relies on provocative maneuvers, including the anterior apprehension, prone external rotation, and FABER tests. Radiographic assessment utilizes the lateral center-edge angle, the femoro-epiphyseal acetabular roof (FEAR) index, and the "cliff sign." Management begins with conservative protocols focusing on periarticular muscle strengthening. For refractory cases, surgical intervention targets the specific pathology. Arthroscopic techniques include labral repair and capsular plication to restore joint tension. In cases of significant osseous deficiency, periacetabular osteotomy (PAO) or femoral derotation osteotomy is indicated to optimize joint coverage and alignment. Minimally invasive PAO techniques have reduced recovery times while maintaining clinical efficacy.

Conclusion: Accurate diagnosis of hip microinstability requires clinical suspicion and comprehensive imaging. Treatment should be individualized, progressing from conservative rehabilitation to targeted surgical stabilization of soft tissues or osseous structures to prevent joint degeneration.