The High Variability in Sizing Knee Cartilage Defects

Background: Articular cartilage defects of the knee are commonly encountered during arthroscopic examination and are believed to be a precursor to osteoarthritis. While a variety of surgical treatments exist, the defect size, specifically the cross-sectional area, has historically been used as a critical element in choosing one procedure over another. The purpose of this study was to characterize the variability associated with arthroscopic techniques that are used to determine the cross-sectional area of distal femoral articular cartilage defects. Methods: Six orthopaedic surgeons used four measurement techniques to estimate the area of cartilage defects in ten cadaveric knees. The areas of the defects determined by the surgeons were compared against the known areas of the defects that were determined from plastic molds. Results: Averaged across all approaches, the four measurement techniques yielded highly variable results that underestimated the size of the defects (mean and standard deviation, −0.31 ± 1.22 cm2). There was no difference in the estimated sizes of the defects on the medial or lateral femoral condyles (p = 0.96), but defects on the trochlea (mean, −0.53 ± 1.00 cm2) were less accurately sized than defects on either of the condyles (p < 0.01). The areas of defects that were <2 cm2 were overestimated (mean, 0.21 ± 0.65 cm2) compared with other sizes of defects (p < 0.001), and the areas of defects that were >4 cm2 were underestimated (mean, −0.87 ± 1.83 cm2) compared with other defects (p < 0.001). Conclusions and Clinical Relevance: Our current treatment algorithms rely heavily on the size of a cartilage defect, but only 57% of the measurements in this study would have accurately led to the appropriate surgical procedure. There is a need to evaluate and quantify the size of a lesion more appropriately than current standards allow and potentially revise existing treatment algorithms.