Biomechanical Assessment of Femoroacetabular Impingement

Inclusion Criteria: * Patients who present with hip pain subsequently diagnosed as femoroacetabular impingement * Subjects who meet the following radiographic criterion of cam or pincer FAI, will be given the opportunity to volunteer in this study. * Subjects that demonstrate a cross-over-sign or a lateral center edge angle (LCEA) without an alpha angle, will be classified as having pincer FAI. * Subjects with an alpha angle, without a cross-over sign or LCEA, will be categorized as having cam type FAI. * Finally, with at least one cam (alpha angle) and pincer sign "cross-over-sign or a lateral center edge angle (LCEA)" will be classified as mixed FAI. Control Population Inclusion Criteria: * 12 controls will consist of volunteers in the same age range as the subject groups (18-35 years). * Control hips will be screened with a standard AP radiograph. Normal volunteers who have radiographic evidence of FAI, dysplasia or other joint deformities will be excluded. Exclusion Criteria: * Subjects who have radiographic evidence of osteoarthritis (Tonnis Grade III or IV) will be excluded as this study focuses on the mechanics of hips before prominent cartilage damage. * Subjects who have had prior procedures to correct FAI or other hip conditions will be excluded (exploratory procedures will be included). * Minors (under age 18), mentally disabled, persons incarcerated, on parole, probation awaiting trial, or pregnant women are excluded from this study. * A human Chorionic Gondaotropin (hCG) urine pregnancy test will be performed on all women prior to the study. * To limit the annual radiation exposure to any participating volunteers, we will exclude anyone who has had a CT scan or participated in a research study involving ionizing radiation in the past 12 months. Motion Capture Exclusion Criteria: * Subjects who are unwilling or unable to perform the proposed activities of daily living or undergo the clinical exams will be dismissed. * Subjects with a BMI less than 30 (www.nhlbisupport.com/bmi/) or those with dense hip musculature/wide hips (maximum of 42 cm of circumferential hip length) will be excluded. CT Exclusion Criteria: * Subjects who are unwilling or unable to remain still. * Subjects who are allergic to contrast agent and/or lidocaine will be dismissed.