Femoroacetabular impingement (FAI) describes subtle structural abnormalities, including femoral asphericity and acetabular overcoverage, which reduce clearance in the hip joint. FAI is a common cause of hip pain for young, athletic adults. The first theme of this dissertation investigated if FAI morphology is more prevalent in athletes and if physical exams could be used to identify individuals with underlying FAI morphology. In a cohort of collegiate football players, 95% were found to have radiographic abnormalities consistent with those seen in FAI patients. This finding not only suggests that athletes, such as football players, may have an increased risk for developing symptomatic FAI, but also highlights that FAI morphology may frequently occur in asymptomatic subjects. In the same cohort, radiographic measures of femoral asphericity and femoral head-neck offset were mildly correlated to maximum internal rotation. As such, athletes with diminished internal rotation in whom hip pain develops should be evaluated for FAI.

Altered articulation in FAI hips is believed to cause chondrolabral damage and may lead to osteoarthritis, but FAI kinematics have not been accurately quantified. To this end, the second theme of this dissertation focused on developing, validating, and applying a dual fluoroscopy and model-based tracking protocol to accurately quantify three-dimensional in vivo hip kinematics. In a cadaver experiment, model-based tracking was compared to the reference standard, dynamic radiostereometric analysis. Model-based tracking was found to have a positional error less than 0.48 mm and rotational error was less than 0.58°. The methodology was then applied to evaluate a cohort of asymptomatic control subjects and three patients with differing FAI morphology. The results, which represent the most accurate data collected on hip kinematics to date, demonstrate that hip articulation is a highly complex process, including translation, pelvic motion, no bone contact, and labrum involvement in large ranges of motion. Collected data provide necessary baseline results for future comparison studies and could be used to validate computer simulations of impingement, guide pre-operative planning, and serve as boundary conditions in finite element models investigating chondrolabral mechanics.