Background: Recent studies have demonstrated that trunk control likely plays a role in anterior cruciate ligament (ACL) injury. Yet, the majority of ACL research remains focused on the lower limb, with limited information on the trunk position at the time of injury.
Hypotheses: Athletes experiencing a noncontact ACL injury after a 1-legged landing position their center of mass (COM) more posterior from the base of support (BOS) at initial ground contact in comparison with uninjured athletes. The distance from the COM to the BOS (COM_BOS) is larger in female, as compared with male, athletes during 1-legged landing.
Study Design: Case control study; Level of evidence, 3.
Methods: Movie captures of 20 athletes performing a 1-legged landing maneuver resulting in a torn ACL were compared with matched (for gender, sport, and activity just before landing) movie captures of 20 athletes performing a similar maneuver that did not result in an ACL disruption (controls). The COM_BOS, trunkG angle, and limbG angle (both relative to the gravity vector) were measured in the sagittal plane at initial ground-foot contact. A 2-way ANOVA (injury status x gender) was used to examine the hypotheses.
Results: There was a significant difference in all 3 measures based on injury status but not on gender. The COM_BOS, normalized by femur length, and limbG angle were greater ( = 0.9, P < .001 and = 16°, P = .004, respectively), and the trunkG angle was smaller ( = 12°, P = .016) in the participants who sustained an ACL injury as compared with controls. The average COM was calculated as 38 cm more posterior relative to the BOS in the participants who sustained an ACL injury as compared with controls.
Conclusion: Landing with the COM far posterior to the BOS may be a risk factor for noncontact ACL injury and potentially can be addressed in prevention programs.
Background: The pivot shift is a dynamic test of knee stability that involves a pathologic, multiplanar motion path elicited by a combination of axial load and valgus force during a knee flexion from an extended position.
Purpose: To assess the stabilizing effect of the medial and lateral meniscus on anterior cruciate ligament-deficient (ACL-D) knees during the pivot shift examination.
Study Design: Controlled laboratory study.
Methods: A Lachman and a mechanized pivot shift test were performed on 16 fresh-frozen cadaveric hip-to-toe lower extremity specimens. The knee was tested intact, ACL-D, and after sectioning the medial meniscus (ACL/MM-D; n = 8), lateral meniscus (ACL/LM-D; n = 8), and both (ACL/LM/MM-D; n = 16). A navigation system recorded the resultant anterior tibial translations (ATTs). For statistical analysis an analysis of variance was used; significance was set at P < .05.
Results: The ATT significantly increased in the ACL-D knee after lateral meniscectomy (ACL/LM-D; P < .05) during the pivot shift maneuver. In the lateral compartment of the knee, ATT in the ACL-D knee increased by 6 mm after lateral meniscectomy during the pivot shift (16.6 ± 6.0 vs 10.5 ± 3.5 mm, P < .01 for ACL/LM out vs ACL out). Medial meniscectomy, conversely, had no significant effect on ATT in the ACL-D knee during pivot shift examination (P > .05). With standardized Lachman examination, however, ATT significantly increased after medial but not lateral meniscectomy compared with the ACL-D knee (P < .001).
Conclusion: Although the medial meniscus functions as a critical secondary stabilizer to anteriorly directed forces on the tibia during a Lachman examination, the lateral meniscus appears to be a more important restraint to anterior tibial translation during combined valgus and rotatory loads applied during a pivoting maneuver.
Clinical Relevance: This model may have implications in the evaluation of surgical reconstruction procedures in complex knee injuries.
