Relationship Between Anterior Cruciate Ligament Injury and Meniscus-Bone Angle

The meniscus-bone angle (MBA), defined as the angle formed by the lateral meniscus with respect to the lateral tibial slope, has recently been identified as an intrinsic factor associated with primary anterior cruciate ligament (ACL) injuries. However, no studies have investigated the influence of MBA and other intrinsic factors excluding the influence of extrinsic factors, especially the level of sports activity.

The purpose was to evaluate the intrinsic factors of primary ACL injury while controlling for the effect of sports activity level. It was hypothesized that the MBA would be a significant factor associated with ACL deficiency, irrespective of the sports activity level.

Cross-sectional study; Level of evidence, 3.

A total of 143 knees in 139 patients with ACL injuries (group A) and matched controls (matched by age, sex, and Tegner Activity Scale score), 143 knees in 143 patients without ACL injuries (group N), were evaluated. Patient height, body weight, body mass index, lateral posterior tibial slope angle (LPTSA), medial posterior tibial slope angle (MPTSA), MBA of the lateral meniscus, and relative posterior inclination angle (RPIA; MBA - LPTSA) were evaluated between the 2 groups.

The MBA (group A: 22.3°± 4.5°; group N: 29.1°± 3.7°) and RPIA (group A: 15.0°± 6.1°; group N: 24.1°± 4.1°) were significantly (P < .001) smaller in group A, whereas LPTSA (group A: 7.3°± 3.4°; group N: 5.0°± 2.7°) and MPTSA (group A: 7.1°± 3.0°; group N: 5.6°± 2.4°) were significantly (P < .001) larger. Logistic regression analysis with ACL injury as the dependent variable showed significant differences in MBA (OR, 0.645; 95% CI, 0.579-0.718; P < .01) and LPTSA (OR, 1.3; 95% CI, 1.14-1.48; P < .001) between the 2 groups. The receiver operating characteristic curves for the MBA showed a sensitivity of 76.2% and a specificity of 83.9% with the cutoff value of 25.2° (area under the curve, 0.88).

A low MBA with a cutoff value of 25.2° was the most significant independent factor associated with primary ACL injury when controlling for differences in sports activity level.