Master of Engineering Science
The medial collateral ligament (MCL) is composed of two major components: the deep MCL (dMCL) and superficial MCL (sMCL). Recent indications have raised questions as to the validity of previous descriptions of the MCL’s role in knee stability. Despite the relative likelihood of partial injuries to the sMCL, as opposed to complete tears, the impact of these injuries remains largely misunderstood. This thesis set out to (1) interpret the roles of the sMCL and dMCL; and (2) investigate the effect of partial sMCL injuries on knee stability.
A joint motion simulator was used to determine the role of the dMCL and sMCL, and the effect of partial sMCL injuries. The dMCL governed external rotation limits and transection of the sMCL led to heightened instability in valgus and external rotation. Partial sMCL injuries led to load transfer to co-stabilizing ligaments. This testing methodology will be an important tool in understanding complex knee injuries.
Summary for Lay Audience
Injury of the medial collateral ligament (MCL) is a prominent sports injury which is frequently combined with anterior cruciate ligament (ACL) injury, given the similar role both ligaments play in knee stability. The MCL is comprised of two major parts, the deep MCL (dMCL) and superficial MCL (sMCL). The sMCL resides over-top of the dMCL and is greater in fibre length. Injuries to the MCL have a greater impact on the dMCL, making partial sMCL tears more common than complete sMCL tears.
Previous studies have shown that complete tears of the dMCL and sMCL cause rotational instability of the knee, regardless of the status of the ACL. However, recently, there has been conflicting research regarding the exact role of the dMCL and sMCL in knee stability. In a study of professional soccer teams, only 5 of the 130 sMCL injuries were complete tears , with the remaining 125 of 130 partial tears. Yet only one known in vitro study has investigated partial MCL tears.
As a result, this study intends to:
- Assess the role of the dMCL and sMCL in knee stability, in both ACL intact and deficient knees.
- Create a standardized technique for simulating partial sMCL tears in cadaver knees.
- Determine the effect of partial sMCL injury on knee stability.
Using a joint motion simulator, ligaments’ roles were assessed through knee stability tests on cadavers, identifying the ligaments’ reduced ability to withstand loads, and the knee’s increased instability. The results of the fully intact knee were used as the baseline for comparison to the injured states.
The sMCL was the major medial stabilizer of the knee, with the dMCL being secondary, governing the range of motion limits. Partial tears of the sMCL had a more significant reduction in knee stability than its ability to withstand force. The results provide a better understanding of the role of the dMCL and sMCL in knee stability and the effect of partial injuries. This knowledge can help to improve surgical reconstruction techniques, motivate the development of new clinical tests for partial sMCL injuries, optimize patient recovery, and reduce injury time.
Doughty, Callahan, "Biomechanical Investigation of Complete and Partial Medial Collateral Ligament Injuries" (2022). Electronic Thesis and Dissertation Repository. 8585.
Available for download on Friday, September 01, 2023