Patient and alignment factors associated with the occurrence and subtype differentiation of degenerative medial meniscus tears: a weighted comparative analysis

Horizontal and posterior root tears are the two most common degenerative medial meniscal (MM) tear subtypes, yet the patient-related factors predisposing individuals to either pattern remain unclear. Therefore, this study aimed to (1) identify patient-related factors associated with degenerative MM tears and to (2) assess these factors across degenerative tear subtypes, including medial meniscus horizontal tears (MMHTs) and posterior root tears (MMPRTs). Patients who underwent surgical treatment for degenerative MM tears between 2018 and 2024 were retrospectively reviewed. Among them, patients with isolated MMHTs or MMPRTs without radiographic osteoarthritis beyond minimal change were included as the degenerative tear group (Group 1). Additionally, individuals who presented during the same period with knee contusion and demonstrated no definite intra-articular pathology on magnetic resonance imaging were designated as the control group (Group 2). After inverse probability of treatment weighting (IPTW) using age, sex, and Kellgren-Lawrence grade as confounders, between-group comparisons were conducted for demographic and radiologic parameters. In addition, Group 1 was subdivided into patients with MMHTs (Group H) and MMPRTs (Group R), and subgroup comparative analyses were subsequently performed. A total of 84 patients were included (Group 1: n = 56; Group 2: n = 28). After IPTW, body mass index (BMI) and hip–knee–ankle (HKA) angle were significantly higher in Group 1 than in Group 2 (P = 0.009 and 0.048, respectively). In subgroup analyses, no significant differences were found between Group 2 and Group H, whereas Group R showed higher BMI and more varus-aligned parameters compared with Group 2. Subsequent logistic regression analyses demonstrated that BMI was independently associated with the presence of degenerative MM tears (Group 1 vs. 2: P = 0.034), whereas both BMI and HKA were independently associated with MMPRTs (Group 2 vs. R: P = 0.001 and P = 0.004, respectively; Group H vs. R: P = 0.001 and P = 0.005, respectively). Higher BMI was independently associated with the occurrence of degenerative MM tears. In particular, both elevated BMI and HKA angle were independent predictors of MMPRTs, whereas no independent predictors were identified for MMHTs.