Appropriate knee loading during walking is essential for optimal health of mechanosensitive joint tissues and is largely governed by quadriceps muscle forces. However, individuals with anterior cruciate ligament reconstruction (ACLr) often exhibit quadriceps muscle dysfunction conventionally measured via reduced peak knee extensor moments (pKEM). Recent advances in ultrasound imaging provide a unique opportunity to determine if quadriceps dysfunction also manifests as altered contractile behavior between those with ACLr and uninjured controls. PURPOSE: Determine differences in quadriceps contractile behavior during weight acceptance in walking between ACLr, contralateral, and control limbs. METHODS: Six individuals to date with unilateral ACLr (4 females, 20±2 yrs, BMI: 25.3±1.8, months post-surgery: 7.1±0.7) and 11 uninjured controls (6 females; 24±3 yrs, BMI: 22.0±2.0) walked for 2 min on an instrumented treadmill. We collected motion capture and ground reaction force data and recorded cine B-mode ultrasound images of the vastus lateralis (VL). We quantified pKEM, knee flexion excursion (KFE), and VL fascicle length change during weight acceptance (i.e., heel-strike to the instant of pKEM). We report effect sizes (ES) for all comparisons. RESULTS: pKEM was 25% lower in the ACLr limb (0.18±0.18 Nm/kg) than the contralateral limb (0.24±0.11 Nm/kg, ES=0.40) and 75% lower than for uninjured controls (0.74±0.19 Nm/kg, ES=3.03). Similarly, the ACLr limb exhibited 21% less KFE (11.4±3.4°) than the contralateral limb (14.5±2.2°, ES=1.08) and 32% less KFE than in uninjured controls (16.8±3.5°, ES=1.57). In uninjured controls, VL fascicles shortened by 0.13±0.23 cm during weight acceptance despite 1.21±0.26 cm of muscle-tendon-unit lengthening, alluding to a predominant role of tendon elongation. VL fascicles in the contralateral limb of ACLr subjects also exhibited shortening during weight acceptance (0.07±0.33 cm). Conversely, we observed fundamentally different behavior in the ACLr limb, for which VL fascicles lengthened by 0.10±0.14 cm (vs controls, ES=1.21). CONCLUSION: ACLr alters quadriceps contractile behavior during weight acceptance in walking. Fascicle lengthening unique to the ACLr limb may be a functional consequence of quadriceps dysfunction relevant to altered knee loading.
The objective of this study was to compare the vertical (vGRF), anterior-posterior (apGRF), and medial-lateral (mlGRF) ground reaction force (GRF) profiles throughout the stance phase of gait (1) between individuals 6 to 12 months post-anterior cruciate ligament reconstruction (ACLR) and uninjured matched controls and (2) between ACLR and individuals with differing radiographic severities of knee osteoarthritis (KOA), defined as Kellgren and Lawrence (KL) grades KL2, KL3, and KL4.
Individuals with anterior cruciate ligament reconstruction (ACLR) often walk with a less dynamic vertical ground reaction force (vGRF), exemplified by a reduced first peak vGRF and elevated midstance vGRF compared to uninjured controls. However, the mechanism by which altered limb loading affects actual tibial plateau contact forces during walking remains unclear. Our purpose was to use musculoskeletal simulation to evaluate the effects of first peak vertical ground reaction force (vGRF) biofeedback on bilateral tibiofemoral contact forces relevant to the development of post-traumatic osteoarthritis (OA) in 20 individuals with ACLR. We hypothesized that reduced first peak vGRF would produce less dynamic tibial plateau contact forces during walking in individuals with ACLR. As the pivotal outcome from this study, and in support of our hypothesis, we found that less dynamic vGRF profiles in individuals with ACLR - observations that have associated in prior studies with more cartilage breakdown serum biomarkers and reduced proteoglycan density - are accompanied by less dynamic tibiofemoral joint contact forces during walking. We conclude that more sustained limb-level loading, a phenotype that associates with worse knee joint health outcomes following ACLR and was prescribed herein using biofeedback, alters the loading profile and magnitude of force applied to tibiofemoral cartilage.
Individuals with knee joint pathologies exhibit quadriceps dysfunction that, during walking, manifests as smaller peak knee extensor moment (pKEM) and reduced knee flexion excursion. These changes persist despite muscle strengthening and may alter stance phase knee joint loading considered relevant to osteoarthritis risk. Novel rehabilitation strategies that more directly augment quadriceps mechanical output during functional movements are needed to reduce this risk. As an important first step, we tested the efficacy of real-time biofeedback during walking to prescribe changes of ±20% and ±40% of normal walking pKEM values in 11 uninjured young adults. We simultaneously recorded knee joint kinematics, ground reaction forces, and, via ultrasound, vastus lateralis (VL) fascicle length change behavior. Participants successfully responded to real-time biofeedback and averaged up to 55% larger and 51% smaller than normal pKEM values with concomitant and potentially favorable changes in knee flexion excursion. While the VL muscle-tendon unit (MTU) lengthened, VL fascicles accommodated weight acceptance during walking largely through isometric, or even slight concentric, rather than eccentric action as is commonly presumed. Targeted pKEM biofeedback may be a useful rehabilitative and/or scientific tool to elicit desirable changes in knee joint biomechanics considered relevant to the development of osteoarthritis.
Bilateral changes in gait are exhibited following unilateral anterior cruciate ligament reconstruction (ACLR), suggesting that intervention strategies are needed to simultaneously elicit changes in both limbs. Cueing a change in vertical ground reaction force impact peak (vGRF-IP) with real-time gait biofeedback (RTGBF) can alter peak knee flexion angle (pKFA) and knee extension moment (pKEM) in the ACLR limb; yet, the capacity to elicit bilateral changes to pKFA and pKEM using RTGBF is unknown. PURPOSE: Compare bilateral changes in pKFA and pKEM during three force-modifying RTGBF conditions in individuals 6-12 mo. post-ACLR. METHODS: 20 participants (11 F, 25 ± 3 kg/m2, 8 ± 3 mo. post-ACLR) completed 4 randomized RTGBF walking conditions (High, Low, Symmetrical, and Control). High and Low Conditions cued a 5% increase or decrease in each limb's baseline vGRF-IP, respectively, and the Symmetrical Condition cued symmetric vGRF-IP between limbs. pKFA and pKEM change scores from the first 50% of stance were calculated with respect to the Control Condition and compared using 2 (limb) x 3 (condition) repeated measures ANOVAs and Bonferroni corrected planned comparisons. RESULTS: There were no significant condition x limb nor limb effects on ΔpKFA or ΔpKEM; yet, there were significant condition effects for ΔpKFA and ΔpKEM. The ΔpKFA and ΔpKEM were larger in magnitude in High and Low Conditions compared to Symmetrical Condition, but there were no differences in ΔpKFA and ΔpKEM between High and Low Conditions (Table 1). CONCLUSION: Cueing changes in vGRF-IP with RTGBF can bilaterally modify ΔpKFA and ΔpKEM. Although ΔpKEM is not different between the High and Low Conditions, the larger vGRF-IP and 3° average increase in pKFA from the High Condition may be more appropriate for cueing normal knee biomechanics compared to the Low Condition which cues a lower vGRF and a 7° average increase in pKFA. FUNDING SOURCE: National Institutes of Health, NIAMS (1R21AR074094-01)
Serum cartilage oligomeric matrix protein (sCOMP) is used to measure acute biochemical joint tissue response to loading. Greater delayed sCOMP post-loading is linked to femoral cartilage thinning over 5 years. It remains unclear if sCOMP response to loading is associated with early femoral cartilage compositional changes linked to osteoarthritis development. PURPOSE: The purpose of this cross-sectional study was to estimate the associations between changes in sCOMP after a standardized walking protocol and femoral cartilage composition in individuals with anterior cruciate ligament reconstruction (ACLR). METHODS: Serum was collected before, immediately after, and 3.5 hours after a standardized 3,000 step walking protocol conducted at each participant's self-selected speed (speed = 1.2 ± 0.1 m/s). sCOMP changes were calculated as the difference in concentrations from before to immediately and 3.5 hours after walking. Enzyme-linked immunosorbent assays were used to assess sCOMP (mean intra-assay variability = 15%). T1ρ relaxations times were collected bilaterally using magnetic resonance imaging and weightbearing portions of the cartilage were segmented into medial (MFC) and lateral (LFC) femoral condylar regions. Regional interlimb ratios were calculated by dividing mean T1ρ relaxation times in the ACLR limb by the non-injured limb. Greater T1ρ interlimb ratios were interpreted as lower proteoglycan density (worse cartilage composition) in the ACLR relative to the non-injured limb. Linear regressions were used to determine the association between change in sCOMP and T1ρ relaxation times after controlling for sex and months since surgery. RESULTS: 19 participants (9 male/10 female, 20.5 ± 4.1 years old, 24.8 ± 3.1 kg/m2 BMI, 7.3 ± 1.5 months since surgery) completed the study. Greater LFC T1ρ interlimb ratios were associated with greater increases in COMP at 3.5 hours (∆R2 = 0.28, p = 0.03), but not immediately (∆R2 = 0.08, p = 0.32) after walking. Associations between MFC T1ρ interlimb ratios and changes in sCOMP after walking were not statistically significant (p = 0.57-0.82). CONCLUSIONS: Delayed increases in sCOMP concentrations after walking may be more closely linked to deleterious cartilage metabolism and may be a better marker of early degenerative changes in knee joint health than acute changes.
Insufficient quadriceps force production and altered knee joint biomechanics after anterior cruciate ligament reconstruction (ACLR) may contribute to a heightened risk of osteoarthritis. Quadriceps muscle lengthening dynamics affect force production and knee joint loading; however, no study to our knowledge has quantified in vivo quadriceps dynamics during walking in individuals with ACLR or examined correlations with joint biomechanics. Our purpose was to quantify bilateral vastus lateralis (VL) fascicle length change and the association thereof with gait biomechanics during weight acceptance in individuals with ACLR. The authors hypothesized that ACLR limbs would exhibit more fascicle lengthening than contralateral limbs. The authors also hypothesized that ACLR limbs would exhibit positive correlations between VL fascicle lengthening and knee joint biomechanics during weight acceptance in walking. The authors quantified VL contractile dynamics via cine B-mode ultrasound imaging in 18 individuals with ACLR walking on an instrumented treadmill. In partial support of our hypothesis, ACLR limb VL fascicles activated without length change on average during weight acceptance while fascicle length on the contralateral limb decreased on average. The authors found a positive association between fascicle lengthening and increase in knee extensor moments in both limbs. Our results suggest that examining quadriceps muscle dynamics may elucidate underlying mechanisms relevant to osteoarthritis.