The medial knee gap measured on ultrasound images is wider during a valgus stress test compared to the anterior medial knee rotation test

Abstract

ObjectivesPatients with injuries to the deep fibers of the medial collateral ligament (dMCL) have a worse prognosis than patients with injuries to the superficial fibers (sMCL). The anterior medial (ANTMED) rotation test has been developed to differentiate between injuries to the dMCL and sMCL. The current study tested the hypothesis that the width of the medial knee gap would be greater during the valgus stress test than the ANTMED rotation test.MethodsFifty‐three participants were included in the study. Participants did not have a history of knee injury. Ultrasound images of the participants' medial knees were collected during the valgus stress test and the ANTMED rotation test. Repeated measures ANOVA was used to test differences in the medial knee gap between the tests, stress condition, and side.ResultsNo difference between the tests in the medial knee joint gap width in the no‐stress condition. The increase in the joint gap width was greater during the valgus stress test than the ANTMED rotation test. The medial knee gap increased during both the valgus stress (4.0 ± 0.12 mm) and the ANTMED rotation test (2.9 ± 0.12 mm).ConclusionsA greater increase in the medial knee gap was seen during the valgus stress test compared to the ANTMED rotation test. Knee external rotation increases the tension within the dMCL. Increased tension in the dMCL could explain the test differences in the increase in the joint gap found in the current study. The ANTMED rotation test may prove useful to identify injury to the dMCL.