Interrater Reliability of a Clinical Scale to Assess Knee Joint Effusion

STUDY DESIGN: Clinical measurement. OBJECTIVE: To determine the interrater reliability of a knee joint effusion grading scale in an outpatient orthopaedic physical therapy clinic. BACKGROUND: Knee joint effusion may indicate joint inflammation or irritation. Therefore, objective monitoring of effusion is important to decision making regarding patient prognosis and program progression. The clinicians in the authors' clinic use a modified stroke test to assess for knee joint effusion, which is operationally based on a 5-point grading scale. METHODS: Seventy-five patients (44 male, 31 female) receiving outpatient physical therapy for a unilateral knee problem, for whom effusion assessment was indicated, were tested. The subjects ranged from 16 to 65 years of age. Pairs of therapists graded the knee joint effusion using the clinical grading scale. A contingency table was constructed and analyzed using Cohen kappa values to establish interrater reliability. Percent agreement was also calculated. RESULTS: The kappa value was 0.75, observed as a proportion of the maximum possible kappa, and the percent agreement was 73%. Fifty-four of 75 pairs of tests had perfect agreement. Only 5 had disagreement of 2 grades, and there were no disagreements of greater than 2 grades. CONCLUSION: These findings provide evidence to support the proposed clinical effusion grading scale as a reliable method to assess knee joint effusion between therapists in an outpatient orthopaedic physical therapy clinic in patients with unilateral knee dysfunction. Only 5 of 75 ratings resulted in disagreement that could result in different clinical decisions being made by the therapists.