The purpose of this study was to compare gait biomechanics between limbs and to matched uninjured controls (i.e., sex, age, and body mass index) preoperatively and at 2, 4, 6, and 12 months following primary unilateral anterior cruciate ligament reconstruction (ACLR). Functional mixed effects models were used to identify differences in gait biomechanics throughout the stance phase between the a) ACLR limb and uninvolved limb, b) ACLR limb and controls, and c) uninvolved limb and controls. Compared with the uninvolved limb, the ACLR limb demonstrated lesser knee extension moment (KEM; within 8–37% range of stance) during early stance as well as lesser knee flexion moment (KFM; 45–84%) and greater knee flexion angle (KFA; 43–90%) during mid‐ to late stance at all timepoints. Compared with controls, the ACLR limb demonstrated lesser vertical ground reaction force (vGRF; 5–26%), lesser KEM (7–47%), and lesser knee adduction moment (KAM; 12–35%) during early stance as well as greater vGRF (39–63%) and greater KFA (34–95%) during mid‐ to late stance at all timepoints. Compared with controls, the uninvolved limb demonstrated lesser KFA (1–56%) and lesser KEM (12–54%) during early to mid‐stance at all timepoints. While gait becomes more symmetrical over the first 12 months post‐ACLR, the ACLR and uninvolved limbs both demonstrate persistent aberrant gait biomechanics compared to controls. Biomechanical waveforms throughout stance can be generally described as less dynamic following ACL injury and ACLR compared with uninjured controls.

Continuous monitoring of knee motion can provide deep insights into patients’ rehabilitation status after knee injury and help to better identify their individual therapeutic needs. Potentiometers have been identified as one possible sensor type for continuous monitoring of knee motion. However, to verify their use in monitoring real-life environments, further research is needed. We aimed to validate a potentiometer-embedded knee brace to measure sagittal knee kinematics during various daily activities, as well as to assess its potential to continuously monitor knee motion. To this end, the sagittal knee motion of 32 healthy subjects was recorded simultaneously by an instrumented knee brace and an optoelectronic reference system during activities of daily living to assess the agreement between these two measurement systems. To evaluate the potentiometer’s behavior during continuous monitoring, knee motion was continuously recorded in a subgroup (n = 9) who wore the knee brace over the course of a day. Our results show a strong agreement between the instrumented knee brace and reference system across all investigated activities as well as stable sensor behavior during continuous tracking. The presented potentiometer-based sensor system demonstrates strong potential as a device for measuring sagittal knee motion during daily activities as well as for continuous knee motion monitoring.

Context: Gait biomechanics and daily steps are important aspects of knee-joint loading that change after anterior cruciate ligament reconstruction (ACLR). Understanding their relationship during the first 6 months post-ACLR could help clinicians develop comprehensive rehabilitation interventions that promote optimal joint loading after injury, thereby improving long-term knee-joint health. Objectives: To compare biomechanical gait waveforms throughout stance at early time points post-ACLR in individuals with different daily step behaviors at 6 months post-ACLR and to examine how these gait waveforms compare with those of uninjured controls. Design: Case-control study. Setting: Laboratory. Patients or Other Participants: A total of 32 individuals with primary ACLR assigned to the low-step group (LSG; n = 13) or the high-step group (HSG; n = 19) based on their average daily steps at 6 months post-ACLR and 32 uninjured matched controls. Main Outcome Measure(s): Gait biomechanics were collected at 2, 4, and 6 months post-ACLR for the ACLR groups and at a single session for the control group. Knee-adduction moment, knee-extension moment (KEM), and knee-flexion angle (KFA) waveforms were calculated during gait stance and then compared via functional waveform analyses. Mean differences and corresponding 95% CIs between groups were reported. Results: Primary results demonstrated less KFA (1%–45% versus 79%–92% of stance) and greater KEM (65%–93% of stance) at 2 months and greater knee-adduction moment (14%–20% versus 68%–92% of stance) at 4 months post-ACLR for the HSG compared with the LSG. Knee-adduction moment, KEM, and KFA waveforms differed across various proportions of stance at all time points between the step and control groups. Conclusions: Differences in gait biomechanics were present at 2 and 4 months post-ACLR between step groups, with the LSG demonstrating an overall more flexed knee and more profound stepwise underloading throughout stance than the HSG. The results indicate a relation between early gait biomechanics and later daily step behaviors post-ACLR.

Time spent in moderate-to-vigorous physical activity (MVPA) is linked to biomarkers associated with knee osteoarthritis development following anterior cruciate ligament reconstruction (ACLR). It remains unclear whether distinct MVPA trajectories exhibited during the first 12 months post-ACLR are linked to early markers of knee osteoarthritis. Purpose: To identify distinct MVPA trajectories between 2 and 12 months post-ACLR and compare tibiofemoral articular cartilage composition changes and patient-reported outcomes (PROs) between trajectory groups. Methods: Device-measured MVPA was collected at 2, 4, 6, and 12 months post-ACLR in individuals with ACLR. MVPA trajectories were identified using group-based trajectory modeling. Cartilage composition was measured preoperatively and at 12 months post-ACLR using change in T1ρ (ΔT1ρ) magnetic resonance imaging relaxation times in the lateral (lateral femoral condyle [LFC], lateral tibia) and medial (medial femoral condyle, medial tibia) femoral and tibial compartments. The Knee Injury and Osteoarthritis Outcomes Score (KOOS) was used to assess PROs preoperatively and at 2, 4, 6, and 12 months post-ACLR. Differences in KOOS subscale scores and ΔT1ρ were compared between MVPA trajectory groups. Results: We identified a consistent MVPA (74.5%) and a high-increasing MVPA trajectory (25.5%). The high-increasing trajectory group engaged in more MVPA at all time points compared with the consistent group. The high-increasing trajectory group demonstrated greater ΔT1ρ in the LFC (i.e., deleterious changes in cartilage composition, P = 0.006) and higher KOOS sport compared with the consistent MVPA group ( P = 0.037). Conclusions: Individuals between 2 and 12 months post-ACLR most commonly engage in the consistent MVPA trajectory. The high-increasing MVPA trajectory group demonstrated worsening LFC cartilage composition. These data indicate that high MVPA in the first 12 months post-ACLR may be linked to deleterious knee tissue changes but not worse PROs.