Assessment of range of motion and contact zones with commonly performed physical exam manoeuvers for femoroacetabular impingement (FAI): what do these tests mean?

Recognition of the magnitude and location of mechanical conflicts is critical to reliably and reproducibly improve functional range of motion and outcomes after surgical treatment of femoroacetabular impingement (FAI). The purpose of this study was to assess the ROM and location of intra-articular and extra-articular mechanical conflict with seven commonly performed physical exam manoeuvers in a cohort of hips with symptomatic FAI. Internal rotation in flexion results in mechanical contact between the anterolateral and anterior femoral head-neck junction with the acetabulum, most commonly at a 1:15 o'clock position. Associated adduction, however, significantly reduces the available internal rotation secondary to contact in the same locations. Straight abduction results in mechanical conflict between the superior femoral head-neck junction and the 12:00 o'clock position of the acetabulum. With external rotation of the hip in various degrees of hip flexion, the potential mechanical impingement is extra-articular between the greater trochanter and ischium or pubic ramus. The zones of proximal femoral and acetabular contact are not intuitive, and may extend significantly more laterally and distally on the femoral head-neck junction than previously appreciated.