PURPOSE: This study was undertaken to report clinical outcomes after high tibial osteotomy (HTO) in patients with a discoid lateral meniscus and to determine (1) whether discoid lateral meniscus degeneration by magnetic resonance imaging (MRI) progresses after HTO and (2) whether this progression adversely affects clinical results. METHODS: The records of 292 patients (292 knees) who underwent medial opening HTO were retrospectively reviewed, and discoid types and grades of lateral meniscus degeneration as determined by MRI were recorded preoperatively. Of the 292 patients, 17 (5.8%) had a discoid lateral meniscus, and postoperative MR images were obtained at least 2 years after HTO for 15 of these 17 patients. RESULTS: American Knee Society (AKS) pain, knee and function scores significantly improved in the 15 patients after surgery (p < 0.001). Eight (53%) had an incomplete and 7 (47%) had a complete discoid lateral meniscus. By preoperative MRI, the distribution of meniscal degeneration was as follows: grade 1, 4 patients; grade 2, 7 patients; and grade 3, 4 patients. At the final follow-up, the distribution of degeneration was as follows: grade 1, 2 patients; grade 2, 5 patients; and grade 3, 8 patients. Two patients with grade 3 degeneration who did not undergo partial meniscectomy showed tear progression. Thus, 8 of the 15 patients (53%) experienced progressive discoid meniscal degeneration after HTO. Median AKS pain score was significantly lower in the progression group than in the non-progression group (40 vs 45, respectively). CONCLUSION: The results of this study suggest that increased load on the lateral compartment after HTO can accelerate discoid lateral meniscus degeneration by MRI and caution that when a discoid lateral meniscus is found by preoperative MRI, progressive degeneration may occur after HTO and clinical outcome may be adversely affected. LEVEL OF EVIDENCE: Therapeutic study, Level IV.
PURPOSE: This study was undertaken to report clinical outcomes after high tibial osteotomy (HTO) in patients with a discoid lateral meniscus and to determine (1) whether discoid lateral meniscus degeneration by magnetic resonance imaging (MRI) progresses after HTO and (2) whether this progression adversely affects clinical results. METHODS: The records of 292 patients (292 knees) who underwent medial opening HTO were retrospectively reviewed, and discoid types and grades of lateral meniscus degeneration as determined by MRI were recorded preoperatively. Of the 292 patients, 17 (5.8%) had a discoid lateral meniscus, and postoperative MR images were obtained at least 2 years after HTO for 15 of these 17 patients. RESULTS: American Knee Society (AKS) pain, knee and function scores significantly improved in the 15 patients after surgery (p < 0.001). Eight (53%) had an incomplete and 7 (47%) had a complete discoid lateral meniscus. By preoperative MRI, the distribution of meniscal degeneration was as follows: grade 1, 4 patients; grade 2, 7 patients; and grade 3, 4 patients. At the final follow-up, the distribution of degeneration was as follows: grade 1, 2 patients; grade 2, 5 patients; and grade 3, 8 patients. Two patients with grade 3 degeneration who did not undergo partial meniscectomy showed tear progression. Thus, 8 of the 15 patients (53%) experienced progressive discoid meniscal degeneration after HTO. Median AKS pain score was significantly lower in the progression group than in the non-progression group (40 vs 45, respectively). CONCLUSION: The results of this study suggest that increased load on the lateral compartment after HTO can accelerate discoid lateral meniscus degeneration by MRI and caution that when a discoid lateral meniscus is found by preoperative MRI, progressive degeneration may occur after HTO and clinical outcome may be adversely affected. LEVEL OF EVIDENCE: Therapeutic study, Level IV.