Influence of individual characteristics on static rotational knee laxity using the Rotameter

Purpose: The purpose of this study was to evaluate the influence of individual characteristics on rotational knee laxity in healthy participants. Our second aim was to verify whether the contralateral knee of patients with a non-contact ACL injury presents greater rotational knee laxity than a healthy control group. Methods: Sixty healthy participants and 23 patients having sustained a non-contact ACL injury were tested with a new Rotameter prototype applying torques up to 10 Nm. Multiple linear regressions were performed to investigate the influence of gender, age, height and body mass on rotational knee laxity and to establish normative references for a set of variables related to rotational knee laxity. Multiple analyses of covariance were performed to compare the contralateral knee of ACL-injured patients and healthy participants. Results: Being a women was associated with a significantly (P < 0.05) higher rotational knee laxity, and increased body mass was related to lower laxity results. In the multiple analyses of covariance, gender and body mass were also frequently associated with rotational knee laxity. When controlling for these variables, there were no differences in measurements between the contralateral leg of patients and healthy participants. Conclusion: In the present setting, gender and body mass significantly influenced rotational knee laxity. Furthermore, based on these preliminary results, patients with non-contact ACL injuries do not seem to have excessive rotational knee laxity. Level of evidence: Retrospective comparative study, Level III.