Lateral Meniscus Hypermobility Is Associated With Popliteomeniscal Fascicle Injuries in Patients With Varus Knee Osteoarthritis Undergoing Medial Opening-Wedge High Tibial Osteotomy.

Purpose: To evaluate the association between arthroscopically detected lateral meniscus (LM) hypermobility and popliteomeniscal fascicle (PMF) injuries in patients with varus knee osteoarthritis undergoing medial opening-wedge high tibial osteotomy (MOWHTO). Methods: Patients with varus knee osteoarthritis who underwent MOWHTO were retrospectively reviewed. During arthroscopic observation before osteotomy, the presence of LM hypermobility and PMF tears was assessed. Tom's test was performed under standardized negative pressure using an arthroscopic suction system. LM hypermobility was defined as complete posterior translation of the LM beyond the midpoint of the lateral tibial plateau without major tear. The association between LM hypermobility and PMF tear was analyzed using logistic regression. Results: LM hypermobility was detected in 72 of 136 knees. PMF tears were observed in 65 knees. LM hypermobility was significantly associated with PMF tears. Among the entire cohort, 33 knees had partial-type discoid lateral meniscus (DLM), and 3 knees had complete-type DLM. Among the hypermobile LM group, 21 knees presented with partial or complete DLM, whereas only 15 knees in the stable LM group had DLM. However, this difference was not statistically significant. Demographic characteristics including age, body mass index, preoperative mechanical axis, and Kellgren-Lawrence grade were comparable between the LM hypermobile and stable groups. No significant differences in clinical symptoms related to the lateral compartment were observed between groups. Conclusions: LM hypermobility is a frequent arthroscopic finding in patients undergoing MOWHTO and is significantly associated with PMF tears. Despite the absence of preoperative lateral symptoms, LM instability may represent a relevant intraoperative consideration. Level of Evidence: Level IV, retrospective case series.