Reliability in arthroscopic grading of cartilage lesions: results of a prospective blinded study for evaluation of inter-observer reliability

Arthroscopy is a well-established method for grading cartilage lesions. This study was undertaken to evaluate the inter-observer variance of grading cartilage lesions in a real life operation. Four experienced arthroscopic surgeons used diagnostic arthroscopy, one after the other, to grade cartilage lesions in a total of 16 patients who had undergone knee arthroscopy. In summary, a total of 14 cartilage areas in 16 patients were graded (n = 224). The Cohens (Fleiss) Kappa Index for multiple investigators was kappa = 0.052 in the medial, kappa = 0.300 in the central, and kappa = 0.107 in the lateral surface of the patella. The indices were kappa = 0.292 in the medial, kappa = 0.0.255 in the central, and kappa = 0.234 in the lateral surface of the trochlea. The inter-observer variance was kappa = 0.193 in the MFC mean bearing zone, kappa = 0.116 in the margin of the MFC, kappa = 0.168 in the mean bearing zone of the TM, and kappa = 0.164 in the TM margin. In the lateral compartment, the kappa-Index was 0.309 in the LFC mean bearing zone, 0.111 in the margin of the LFC, 0.020 in the mean bearing zone of the TL, and 0.085 in the TL margin. The inter-observer reliability of the arthroscopic grading of cartilage lesions is poor. The major problem is the relatively large variability in differentiating between intact cartilage and lesions that consist of the softening of the cartilage and the differentiation between superficial and deep cartilage lesions. In the future, objective measurements should be developed to solve this problem.