Femoroacetabular impingement (FAI) is one of the most common mechanisms leading to the development of early cartilage and labral damage in the non-dysplastic hip. Anatomic abnormalities of the proximal femur and/or acetabulum result in repetitive injury during dynamic hip motion, leading to abnormal regional loading of the femoral head-neck junction against the acetabular rim. The resulting damage to the cartilage, labrum, and surrounding capsular structures predispose the patient to developing hip pain and early osteoarthritic changes. Clinically, patients with FAI are a heterogeneous group, with a wide array of presentation from pain to instability that may or may not be related to activity. To date no studies have identified specific prognostic indicators associated with successful surgical treatment of FAI, leaving surgeons without adequate criteria to determine which patients are best suited for arthroscopy. The investigators propose to address this critical knowledge gap by identifying the patient characteristics and morphological features of the hip that are associated with the optimal clinical outcomes in patients undergoing hip arthroscopy or non-operative management for treatment of suspected FAI in order to establish a treatment algorithm for FAI patients.

Inclusion Criteria:

• All patients 35 years of age or younger enrolled in the HSS Hip Preservation Registry prior to September 30, 2016 with an MRI confirmed diagnosis of FAI will be eligible for inclusion in this study regardless of surgery status.
• Patients who agree to participate must complete a baseline questionnaire consisting of: 1) Modified Harris Hip Score (MHHS), an overall measure of hip condition; 2) the Hip Outcome Score (HOS), a measure developed specifically for younger active patients that measures quality of life and levels of sports and recreation; and 3) International Hip Outcome Tool (iHOT33), a newly developed hip specific outcome score, which measures a number of subscores relating to physical and social functioning with hip problems.

Exclusion Criteria:

• Patients over age 35 will be excluded as the focus of this study is early changes that may predispose to later degenerative changes.
• Patients undergoing revision hip arthroscopy as their first treatment in the Registry will not be eligible, as these are patients who have failed initial therapy.
• Patients with no complete questionnaires at any time point will be excluded.

35 years of age or younger enrolled in the HSS Hip Preservation Registry prior to September 30, 2016 with an MRI confirmed diagnosis of FAI