Abstract
Background:
Medial meniscal extrusion (MME) is a potential risk factor for early osteoarthritis (OA) following ACL reconstruction (ACLR), as it may reflect impaired meniscal function and altered joint loading. These deficits are particularly relevant during high-impact tasks, like jump-landing, where compensatory strategies may increase post-operative joint stress. Vertical ground reaction force (vGRF) metrics, including peak force and impulse, are sensitive indicators of limb loading asymmetry, but the relationship between MME and vGRF remains underexplored early post-ACLR.
Hypothesis:
We hypothesized that greater MME would be associated with higher peak vGRF and impulse during bilateral countermovement jumping and that MME would be greater in the involved limb four- to six-months post-ACLR.
Methods:
Twenty participants (8 females; Age:19.3±3.6 years; Height:173.7±8.5cm; Weight:82.9±21.9kg; Time Since Surgery:4.4±0.5mo) who had undergone ACLR within the previous four to six-months completed bilateral CMJ trials. Ground reaction forces were collected using a force platform during CMJ trials, capturing peak vGRF and impulse normalized to body mass in both limbs. Each participant completed five trials per limb, and the mean value across trials was used for analysis. MME was assessed via musculoskeletal ultrasound in a standardized supine position and their knee in 20-30° of flexion. Extrusion was defined as the distance from the medial meniscus edge to the tibial plateau border, with values beyond the cortical line indicating displacement outside the joint space. Two images per limb were acquired, and the average was used as MME for analysis. Separate Pearson product-moment correlations were conducted to assess associations between MME and both peak vGRF and impulse in the involved and uninvolved limbs, and a paired t-test was used to compare MME between limbs.
Results:
No significant associations were found between MME and vGRF, however MME was significantly greater in the involved limb compared to the uninvolved limb (p=004;t=3.322). In the involved limb, MME (2.24±1.24mm) was not correlated with peak vGRF (1.46±0.50BW; r=0.229, p=0.332) or impulse (0.20±0.04BW⋅s; r=−0.236, p=0.317). In the uninvolved limb, MME (1.47±0.62 mm) was not correlated with peak vGRF (2.28±0.71BW; r=0.108, p=0.650) or impulse (0.30±0.04BW⋅s; r=0.079, p=0.740).
Conclusion:
Despite the presence of greater MME in the involved limb, MME was not associated with differences in vertical ground reaction force during bilateral CMJ early after ACLR. This may reflect the symmetrical and moderate demands of the task, which could mask compensatory strategies linked to meniscal pathology. Future studies should explore whether MME impacts loading during higher-demand or unilateral tasks, where asymmetries are more likely to emerge.