Increased Rates of Both Knee and Hip Arthroplasties in Older Patients with Ankylosing Spondylitis.

Rates of THA in older patients with AS doubled over recent years, outpacing the increase in the general population. Rates of TKA were also substantially higher in older patients with AS. The increased risk of TKA in AS may be a consequence of damage from knee inflammation, or alterations in lower extremity biomechanics due to hip arthritis.