Tibiofemoral Contact Forces in the Anterior Cruciate Ligament-Reconstructed Knee.

PURPOSE: To investigate differences in ACL reconstructed (ACLR) and healthy individuals in terms of the magnitude of the tibiofemoral contact forces, as well as the relative muscle and external load contributions to those contact forces, during walking, running and sidestepping gait tasks. METHODS: A computational electromyography-driven neuromusculoskeletal model was used to estimate the muscle and tibiofemoral contact forces in those with combined semitendinosus and gracilis tendon autograft ACLR (n=104, 29.7±6.5 years, 78.1±14.4 kg) and healthy controls (n=60, 27.5±5.4 years, 67.8±14.0 kg) during walking (1.4±0.2 ms), running (4.5±0.5 ms) and sidestepping (3.7±0.6 ms). Within the computational model, the semitendinosus of ACLR participants was adjusted to account for literature reported strength deficits and morphological changes subsequent to autograft harvesting. RESULTS: ACLRs had smaller maximum total and medial tibiofemoral contact forces (~80% of control values, scaled to bodyweight) during the different gait tasks. Compared to controls, ACLRs were found to have a smaller maximum knee flexion moment, which explained the smaller tibiofemoral contact forces. Similarly, compared to controls, ACLRs had both a smaller maximum knee flexion angle and knee flexion excursion during running and sidestepping, which may have concentrated the articular contact forces to smaller areas within the tibiofemoral joint. Mean relative muscle and external load contributions to the tibiofemoral contact forces were not significantly different between ACLRs and controls. CONCLUSION: ACLRs had lower bodyweight-scaled tibiofemoral contact forces during walking, running and sidestepping, likely due to lower knee flexion moments and straighter knee during the different gait tasks. The relative contributions of muscles and external loads to the contact forces were equivalent between groups

A longitudinal study of impact and early stance loads during gait following arthroscopic partial meniscectomy

People following arthroscopic partial medial meniscectomy (APM) are at increased risk of developing knee osteoarthritis. High impact loading and peak loading early in the stance phase of gait may play a role in the pathogenesis of knee osteoarthritis. This was a secondary analysis of longitudinal data to investigate loading-related indices at baseline in an APM group (3 months post-surgery) and a healthy control group, and again 2 years later (follow-up). At baseline, 82 participants with medial APM and 38 healthy controls were assessed, with 66 and 23 re-assessed at follow-up, respectively. Outcome measures included: (i) heel strike transient (HST) presence and magnitude, (ii) maximum loading rate, (iii) peak vertical force (Fz) during early stance. At baseline, maximum loading rate was lower in the operated leg (APM) and non-operated leg (non-APM leg) compared to controls (p≤0.03) and peak Fz was lower in the APM leg compared to non-APM leg (p≤0.01). Over 2 years, peak Fz increased in the APM leg compared to the non-APM leg and controls (p≤0.01). Following recent APM, people may adapt their gait to protect the operated knee from excessive loads, as evidenced by a lower maximum loading rate in the APM leg compared to controls, and a reduced peak Fz in the APM leg compared to the non-APM leg. No differences at follow-up may suggest an eventual return to more typical gait. However, the increase in peak Fz in the APM leg may be of concern for long-term joint health given the compromised function of the meniscus

Mechanisms underpinning longitudinal increases in the knee adduction moment following arthroscopic partial meniscectomy

Background Knee osteoarthritis is common following arthroscopic partial meniscectomy and a higher external peak knee adduction moment is believed to be a contributor. The peak knee adduction moment has been shown to increase over 2 years (from 3-months post-arthroscopic partial meniscectomy). The aim of this study was to evaluate mechanisms underpinning the increase in peak knee adduction moment over 2 years observed in people 3-months following arthroscopic partial meniscectomy. Methods Sixty-six participants with medial arthroscopic partial meniscectomy were assessed at baseline and again 2 years later. Parameters were evaluated at time of peak knee adduction moment as participants walked barefoot at their self-selected normal and fast pace for both time points. Findings For normal pace walking, an increase in frontal plane ground reaction force-to-knee lever arm accounted for 30% of the increase in peak knee adduction moment (B = 0.806 [95% CI 0.501–1.110], P < 0.001). For fast pace walking, an increase in the frontal plane ground reaction force magnitude accounted for 21% of the increase in peak knee adduction moment (B = 2.343 [95% CI 1.219–3.468], P < 0.001); with an increase in tibia varus angle accounting for a further 15% (B = 0.310 [95% CI 0.145–0.474], P < 0.001). Interpretation Our data suggest that an increase in lever arm and increase in frontal plane ground reaction force magnitude are contributors to the increased knee adduction moment observed over time in people following arthroscopic partial meniscectomy

Altering foot progression angle in people with medial knee osteoarthritis: the effects of varying toe-in and toe-out angles are mediated by pain and malalignment

SummaryObjectivesTo evaluate if altering the foot progression angle (FPA) by varying magnitudes during gait alters the external knee adduction moment (KAM), knee flexion moment (KFM), knee extension moment (KEM) and/or symptoms in people with medial knee osteoarthritis (OA). Potential influence of pain and knee malalignment on load-modifying effects of FPA was investigated.DesignParticipants (n = 22) underwent 3-dimensional gait analysis to measure KAM peaks, KAM impulse, KFM and KEM peaks. Following natural gait, five altered FPA conditions were performed in random order (10° toe-in, 0° FPA, 10° toe-out, 20° toe-out and 30° toe-out). A projection screen displayed their real-time FPA. Pain/discomfort at knees and feet/ankles were evaluated for each condition. Linear mixed models were used for statistical analysis.ResultsToe-in reduced the early stance peak KAM and KEM but increased the KAM impulse, late stance peak and KFM. Toe-out reduced the KAM impulse, late stance peak and KFM (P < 0.001) but increased the early stance peak KAM and KEM. All effects were greater in participants with more varus knees. Pain significantly mediated the effect of altered FPA on the KAM impulse and late stance peak. In more painful individuals, toe-in was predicted to reduce the KAM impulse and late stance peak, and increase them for toe-out gait. There were no immediate symptomatic changes.ConclusionsEffects of altered FPA vary across all medial knee load parameters and it is difficult to determine an optimal direction of FPA change. Future studies should consider Western Ontario McMaster Universities OA Index (WOMAC) pain to judge the likely effects of altered FPA