Dynamic Restraints of the Medial Side of the Knee: The Semimembranosus Corner Revisited

Abstract

Background: Little is known about the dynamic restraints of the semimembranosus muscle (SM). Purpose and Hypothesis: The goal of the present study was to elucidate the role of (1) passive and (2) active restraints to medial-side instability and to analyze (3) the corresponding tightening of the posteromedial structures by loading the SM. It was hypothesized that points 1 to 3 will significantly restrain medial knee instability. This will aid in understanding the synergistic effect of the semimembranosus corner. Study Design: Controlled laboratory study. Methods: Nine knees were tested in a 6 degrees of freedom robotic setup and an optical tracking system. External rotation (ER; 4 N·m), internal rotation (4 N·m), anteromedial rotation (4-N·m ER and 89-N anterior tibial translation), and valgus rotation (8 N·m) were applied at 0°, 30°, 60°, and 90°, with and without an SM load of 75 N. Sequential cutting of the medial collateral ligament and posterior oblique ligament was then performed. At the intact state of the knee and after each cut, the aforementioned simulated laxity tests were performed. Results: The medial collateral ligament was found to be the main passive stabilizer to ER and anteromedial rotation, resulting in 9.3° ± 6.8° (P < .05), 8.1° ± 3.6° (P < .05), and 7.6° ± 4.2° (P < .05) at 30°, 60°, and 90°, respectively. Conversely, after the posterior oblique ligament was cut, internal rotation instability increased significantly at early flexion angles (9.3° ± 3.2° at 0° and 5.2° ± 1.1 at 30°). Loading the SM had an overall effect on restraining ER (P < .001) and anteromedial rotation (P < .001). This increased with flexion angle and sectioning of the medial structures and resulted in a pooled 2.8° ± 1.7° (not significant), 5.4° ± 2° (P < .01), 7.5° ± 2.8° (P < .001), and 8.3° ± 4.4° (P < .001) at 0°, 30°, 60°, and 90° when compared with the unloaded state. Conclusion: The SM was found to be a main active restraint to ER and anteromedial rotation, especially at higher flexion angles and in absence of the main passive medial restraints. The calculated tensioning effect was small in all flexion angles for all simulated laxity tests. Clinical Relevance: A complete semimembranosus avulsion may indicate severe medial knee injury, and refixation should be considered in multiligament injury.

Posterior Oblique Ligament Repair Concomitant to Anterior Cruciate Ligament Reconstruction

“…4 Biomechanically, the POL is a main stabilizer against internal rotation in early flexion angles (0 -30 ) and is responsible for restraining valgus rotation in extension, whereas the MCL is the major restraint in higher flexion angles. 10,11 Nevertheless, clinical examination remains challenging. Most authors agree that finding of valgus laxity at 0 in an ACL deficient knee indicates a concomitant injury of the posteromedial structures including the POL.…”

Semimembranosus Tendon Advancement for the Anteromedial Knee Rotatory Instability Treatment

“…e5 through a technique of easy reproducibility, based on an easy-to-use anatomical structure that already has a stabilized function in the knee joint (Table 1) (25). The risks of this technique are related to the risk of limiting knee extension and arthrofibrosis due to excessive tension in the tenodesis of the SM tendon and the impossibility of using the SM tendon due to extensive injuries to the medial compartment.…”

“…17,18 Yet, it is not clear in literature when the technique of reconstructing medial structures should or should not contain the reconstruction of posteromedial structures. 4,5,[19][20][21][22][23][24][25] The reinsertion and retensioning of posteromedial structures could establish stability in this region of the knee preserving the dynamic function of the SM muscle tendon. This study aims to describe a technique for the treatment of AMRI associated with MCL reconstruction through the tenodesis of the SM tendon in a more anterior and distal position.…”

O Complexo Medial do Joelho: o Lado que Caiu em Esquecimento

“…2,4,6,9 O SM, ao promover a RI da tíbia e ao tensionar estruturas do CPM com a flexão do joelho, torna-se num estabilizador dinâmico face a forças de RE e de translação anterior da tíbia. 16 De salientar ainda que o LCMp e o SM são estabilizadores do menisco medial, contribuindo para o controlo da translação da tíbia sobre o fémur nos maiores graus de flexão. 10, 16 Assim, compreende-se a importância e complexidade das lesões CMJ.…”

“…16 De salientar ainda que o LCMp e o SM são estabilizadores do menisco medial, contribuindo para o controlo da translação da tíbia sobre o fémur nos maiores graus de flexão. 10, 16 Assim, compreende-se a importância e complexidade das lesões CMJ. Estas podem gerar instabilidade coronal em valgo isolada ou associada a movimentos de rotação e translação da tíbia, a denominada instabilidade rotacional ântero--medial (IRAM).…”