Inclusion Criteria:  Patients who have received or are scheduled to receive a type II or any combination of type II (e.g., type I + II, II + III, or I + II + III) hemipelvectomy surgery without reconstruction or with allograft reconstruction at University of Texas (UT) MD Anderson Cancer Center.  Exclusion Criteria:  Patients whose leg has been or will be amputated by hemipelvectomy surgery. Previous surgery or significant injury to either hip. Relevant surgery, procedure, injury, or condition in the last two years which may affect hip pain or general movement patterns on either side. Diagnosis of osteoarthritis, rheumatoid conditions, cancers, or other conditions which may affect musculoskeletal health. Pregnant women or women nursing an infant. Persons with body mass index (BMI) > 30 and/or waist size > 100 cm (39 in) (these individuals would likely require higher radiation doses than are specified for this study). Persons with a history of significant radiation exposure (greater than 25 mSv), whether occupational or medical in nature. Anyone with a history of medical radiation therapy (for cancer or other conditions) is excluded from the study. Persons with a pacemaker, hearing aid, aneurysm clips or artificial heart valves, and other forms of loose metal implants will be excluded from the study as assessed by a pre-magnetic resonance imaging (MRI) questionnaire administered by the MRI technician at the time of the scan. Radiological exclusion criteria (assessed after magnetic resonance [MR] scan is conducted on the first visit, prior to dynamic stereo X-ray [DSX]/computed tomography [CT] radiation exposure): evidence on preliminary MRI of avascular necrosis (AVN), fracture, slipped capital femoral epiphysis (SCFE), collapsed joint space or advanced osteoarthritis, hip dysplasia, masses, lesions, or other anomalies not consistent with a femoro-acetabular impingement (FAI) diagnosis.