A semimembranosus-related band directed toward the posterior horn of the lateral meniscus: MRI prevalence and relationship to posterior knee stabilizing structures.

OBJECTIVE

To determine the MRI prevalence of the semimembranosus-lateral meniscus (SM-LM) attachment and the imaging plane on which it is most conspicuous, and to evaluate its relationships with the meniscofemoral ligaments and the oblique popliteal ligament (OPL).

MATERIALS AND

METHODS

In this retrospective single-center study, 205 1.5-T knee MRI examinations in patients ≥ 18 years (134 women, 71 men; median age, 38 years) were evaluated by a musculoskeletal radiologist, with a random subset of 100 independently evaluated by a second reader; those with prior ipsilateral knee trauma or surgery or Kellgren-Lawrence grade 3-4 osteoarthritis were excluded. Interobserver agreement was evaluated with Cohen κ; logistic regression and chi-square analyses were performed.

RESULTS

The SM-LM attachment was identified in 32 of 205 knees (15.6%), exclusively thin and most conspicuous on axial images. The ligament of Wrisberg was present in 139 knees (67.8%), the OPL in 129 (62.9%), and the ligament of Humphrey in 113 (55.1%); the meniscofemoral ligaments co-occurred inversely (χ2 = 46.2, p < 0.001). The OPL was inversely associated with the SM-LM attachment on univariable analysis, and this inverse association persisted on multivariable analysis (adjusted OR, 0.42; 95% CI, 0.19-0.91; p = 0.029). Interobserver agreement was substantial to almost perfect (κ range, 0.69-0.94).

CONCLUSION

The SM-LM attachment is an identifiable, thin semimembranosus-related band on knee MRI whose definitive anatomical nature requires cadaveric or surgical correlation. Its inverse association with the OPL suggests that these semimembranosus-related structures may represent alternative patterns within the posterior stabilizing network.