This trial is designed to measure improvement of hip involvement in patients with ankylosing spondylitis (AS) after receiving 4 doses of infliximab. Participants will receive infliximab 5 mg/kg (as an intravenous perfusion over a period of 2 hours) at Weeks 0, 2, 6, and 14, consistent with the approved dosing regimen described in the label. Participants will be evaluated for hip pain, functional capacity and stiffness before and after 14 weeks (4 doses) of treatment. Further treatment after 4 doses is based on standard clinical practice as determined by the trial site.