Use of a New Arthrometer to Assess Knee Pathology

Purpose: The purpose of this study was to compare the results of Mobil-Aider testing on the involved and uninvolved knees of individuals with anterior cruciate ligament (ACL) injuries to MRI results.
Methods: Individuals with reported knee injuries (N=26) were tested for ACL laxity using the Mobil-Aider arthrometer. A foam bolster was used to position the knee in 20-30° flexion. The arthrometer was used to perform a Lachman test on the tibio-femoral joint. The maximal translation of 3 measurements on each knee was recorded. The clinical data and the MRI results were matched.
Result: For the test of between-subject differences, an interaction effect was found between side and MRI result (p = 0.008). A simple main effect was found in between involved versus uninvolved side (p = 0.001). There was no simple main effect size found for MRI result (p = 0.415).
Conclusion: Excessive anterior translation of the knee is part of the patient presentation of an ACL injury. The clinician should also be cognizant of the mechanism of injury, the report of a “pop,” presence of rapid swelling, loss of range of motion, and instability. This is the first study using the Mobil-Aider to assess ACL injuries. Although the device has been validated and determined to be reliable in prior studies of healthy individuals, testing individuals with injuries are important to demonstrate its clinical value. The sample size is limited but the study was adequately powered to be able to state the Mobil-Aider has the potential to provide valuable clinical information when assessing ACL injuries.

Keywords: Knee sprain; ACL injury; Lachman technique; Arthrometer