This study used behavioral assessment techniques to analyze pain in osteoarthritis (OA) patients. Eighty-seven OA patients having chronic knee pain served as subjects. Pain behavior was evaluated using a standard observation method and functional impairment was assessed using the Arthritis Impact Measurement Scales. Data analysis revealed that pain and limitations in physical activities were the most common functional impairments and that the most frequently observed pain behavior was guarded movement. Predictive analyses indicated that disability support status and scores on a Pain Control and Rational Thinking factor of the Coping Strategies Questionnaire (CSQ) were predictive of functional impairment. Patients receiving disability support payments were much more functionally limited than those not receiving this financial support. Patients scoring high on the Pain Control and Rational Thinking factor of the CSQ were much less functionally impaired, walked a 5 m course more rapidly and moved from a standing to a sitting or reclining position more quickly than patients scoring low on this factor. The implications of these results for behavioral treatment of OA knee pain are discussed.