1991 Clinical (History, Physical Examination, Laboratory) Classification Criteria for Osteoarthritis of the Hip, Classification Tree Format*
1. Hip pain
2a. Hip internal rotation <15°
2b. ESR ≤ 45 mm/hour
(If ESR not available, substitute hip flexion ≤115°)
3a. Hip internal rotation ≥ 15°
3b. Pain on hip internal rotation
3c. Morning stiffness of the hip ≤60 minutes
3d. Age > 50 years
* This classification method yields a sensitivity of 86% and a specificity of 75%. ESR = erythrocyte sedimentation rate (Westergren).
R. Altman, G. Alarcon, D. Appelrouth, D. Bloch, D. Borenstein, K. Brandt, et al. The American College of Rheumatology criteria for the classification and reporting of osteoarthritis of the hip. Arthritis Rheum 1991;34:505--514.
Web editor's note: the original publication includes a graphic representation of this tree in Figure 1. Reprints of the entire article are available through the ACR Office upon request.