Excessive frontal plane motion and valgus torques have been linked to knee injuries, particularly in women. Studies have investigated the role of lower extremity musculature, yet few have studied the activation of trunk or "core" musculature on hip and knee kinematics. Therefore, this study evaluated the influence of intentional core engagement on hip and knee kinematics during a single leg squat.
The knee is the most commonly injured joint. The ACL is routinely injured, with risk of injury per exposure 2 to 8 times greater in females than in males. Excessive medial-lateral motion and valgus forces have been shown to be a major contributor to knee injury. While many researchers have studied the influence of knee and hip musculature, less has been studied about the influence of the trunk or "core" musculature on knee kinematics. PURPOSE: To determine the influence of core musculature engagement of females on triplanar motion of the knee during a single leg squat. METHODS: All subjects were evaluated for core strength using Sahrmann's physical therapy evaluation model. Four reflective markers were positioned on the left and right ASIS, right lateral femoral condyle, and right lateral malleolus of 14 female subjects (mean age 22.13 ± 2.87 years). Each subject performed a single leg squat from a six inch step under 2 conditions: core engaged (CORE) and no core engaged (NOCORE). Knee motion was sampled using an APAS motion analysis system. All data were processed using MATLAB. After scaling and time-normalizing, correlation coefficients were determined for knee marker trajectories between individual subjects' CORE trials and the group's mean NOCORE trial. A correlation coefficient of 0.9 was used as a threshold to define similarity between conditions. RESULTS: Similarities were found between CORE and NOCORE conditions in subjects' vertical and anterior-posterior knee motion (CC = 0.952 and 0.941, respectively). In contrast, greater differences were found between CORE and NOCORE conditions in subjects' medial-lateral knee motion (CC = 0.700). Participants showed greater variability in medial-lateral motion during the NOCORE condition. CONCLUSIONS: Core engagement did influence the medial-lateral motion of the knee during single leg squats. This information may have implications for preventing, predicting, and/or rehabilitating knee injuries of females.
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