To assess the reliability of physical examination of the osteoarthritic (OA) knee by rheumatologists, and to evaluate the benefits of standardization.
Forty-two physical signs and techniques were evaluated using a 6 x 6 Latin square design. Patients with mild to severe knee OA, based on physical and radiographic signs, were examined in random order prior to and following standardization of techniques. For those signs with dichotomous scales, agreement among the rheumatologists was calculated as the prevalence-adjusted bias-adjusted kappa (PABAK), while for the signs with continuous and ordinal scales, a reliability coefficient (R(c)) was calculated using analysis of variance. A PABAK of >0.60 and an R(c) of >0.80 were considered to indicate adequate reliability.
Adequate poststandardization reliability was achieved for 30 of 42 physical signs/techniques (71%). The most highly reliable signs identified by physical examination of the OA knee included alignment by goniometer (R(c) = 0.99), bony swelling (R(c) = 0.97), general passive crepitus (R(c) = 0.96), gait by inspection (PABAK = 0.78), effusion bulge sign (R(c) = 0.97), quadriceps atrophy (R(c) = 0.97), medial tibiofemoral tenderness (R(c) = 0.94), lateral tibiofemoral tenderness (R(c) = 0.85), patellofemoral tenderness by grind test (R(c) = 0.94), and flexion contracture (R(c) = 0.95). The standardization process resulted in substantial improvements in reliability for evaluation of a number of physical signs, although for some signs, minimal or no effect of standardization was noted. After standardization, warmth (PABAK = 0.14), medial instability at 30 degrees flexion (PABAK = 0.02), and lateral instability at 30 degrees flexion (PABAK = 0.34) were the only 3 signs that were highly unreliable.
With the exception of physical examinations for instability, a comprehensive knee examination can be performed with adequate reliability. Standardization further improves the reliability for some physical signs and techniques. The application of these findings to future OA studies will contribute to improved outcome assessments in OA.