No patient enrolled after 6 months from the start. The decision to withdraw the study was based on a feasibility reevaluation conducted with investigators.

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.

Inclusion Criteria:

• 18 years of age or older
• Ankylosing spondylitis (AS) diagnosis
• Have all 3 of the following:
• Presence of hip pain (nocturnal inflammatory pain)
• Limitation of hip mobility
• Patient's Global Assessment Visual Analog Scale (0-10 cm) ≥4 cm.
• Inadequate response or intolerance to non-steroidal anti-inflammatory drugs (NSAIDs)
• Eligible to be treated with Infliximab (Remicade®)

Exclusion Criteria:

• Causes of coaxalgia other than coxitis of AS, demonstrated by images or laboratory tests
• Women who are pregnant or nursing or plan to nurse or become pregnant
• Serious infections like sepsis, abscesses.
• History of or current certain infections
• History of or current certain medical conditions