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.
Matrix metalloproteinase-3 (MMP-3) is a degenerative enzyme associated with joint tissue breakdown and has been shown to be a potential biomarker of osteoarthritis. It remains unknown if synovial fluid (SF) MMP-3 concentrations following ACL injury influence gait mechanics. PURPOSE: To compare knee flexion angle (KFA) and internal knee extension moment (KEM) during gait 6 months post-ACLR in individuals with the highest concentrations of SF MMP-3 compared to those with the lowest concentrations of SF MMP-3 collected within the first 14 days of injury. METHODS: Thirty-seven individuals with ACL injury scheduled for primary patellar tendon autograft ACLR (57% females, 21±4 yrs, 23.7±2.8 BMI) participated. Individuals were grouped into highest (HQ; n=9) and lowest (LQ; n=10) quartiles based on MMP-3 knee joint SF concentrations sampled 6+4 days after ACL injury. At 6 months post-ACLR, biomechanics were collected using 3-dimensional motion capture during gait performed at a self-selected speed. Functional analyses of variance were conducted to compare KFA and KEM between HQ and LQ groups throughout stance. Groups were considered different at any percentage of stance where the 95% confidence intervals of the mean differences did not cross zero. Peak differences (PD) and corresponding effect sizes (Cohen’s d) within portions of stance demonstrating differences were also calculated. RESULTS: HQ exhibited lesser knee flexion excursion; KFA was lower during 17-24% of stance (PD: 2.1°, d=0.44) and greater during 48-100% of stance (PD: 4.5°, d=0.93). HQ also exhibited lower KEM during 14-30% and 91-100% of stance (PD: 0.72 BW, d=0.67; PD: 0.33 BW, d=1.42) and greater KEM during 45-72% of stance (PD: 0.44, d=0.76) CONCLUSION: Compared to individuals in the lowest quartile of SF MMP-3, those in the highest exhibited a stiffened knee gait strategy. Pre-surgery levels of MMP-3 following ACL injury may serve as a biomarker predicting worse gait mechanics 6 months post-ACLR.
Individuals with anterior cruciate ligament reconstruction (ACLR) exhibit more regular gait patterns, resulting in more rigid movements compared to controls. Aberrant joint loading post-ACLR is linked to worse T1ρ magnetic resonance imaging (MRI) relaxation times, an outcome associated with osteoarthritis development. Yet, it remains unknown if knee movement regularity during gait associates with knee cartilage composition in individuals with ACLR. PURPOSE: Determine the association between femoral articular cartilage T1ρ MRI relaxation times and knee joint movement regularity during gait. METHODS: T1ρ MRI and gait kinematics were collected in 20 participants with ACLR (13 Females; 21 ± 4 years old; 8 ± 1 months post-ACLR). Femoral articular cartilage from the ACLR and uninjured limbs was segmented into anterior, central, and posterior regions from the weightbearing portions of the medial and lateral condyles. Mean T1ρ relaxation times were extracted from the cartilage in each region and interlimb ratios were calculated (i.e., ACLR / uninjured limb). Greater interlimb T1ρ ratios were interpreted as lesser proteoglycan density (worse cartilage composition) in the injured limb compared to the uninjured limb. Knee kinematics were collected at a self-selected gait speed on a treadmill with an 8-camera 3D motion capture system. Frontal and sagittal plane knee kinematics were extracted, and sample entropy was used to calculate the degree of movement regularity (i.e., lower values reflect more regularity). Pearson's product-moment correlations were conducted to determine the association between T1ρ and movement regularity variables. RESULTS: Greater frontal plane knee movement regularity associated with greater mean T1ρ interlimb ratios in the anterior portions of the lateral (r = -0.44, p = .04) and medial condyles (r = -0.47, p = .03). Greater sagittal plane kinematic regularity associated with greater mean T1ρ interlimb ratios in the anterior portion of the lateral condyle (r = -0.47, p = .03). CONCLUSION: Greater movement regularity was associated with less femoral articular cartilage proteoglycan density which is linked to early osteoarthritis development. We hypothesize that greater movement regularity contributes to less adaptable gait and more concentrated cartilage 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.
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.