Gait Characteristics Associated With a Greater Increase in Medial Knee Cartilage T 1ρ and T 2 Relaxation Times in Patients Undergoing Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Osteoarthritis of the medial tibiofemoral joint (MTFJ) is prevalent among patients undergoing anterior cruciate ligament reconstruction (ACLR). Magnetic resonance T1ρ and T2 relaxation times provide noninvasive methods to quantify early cartilage degeneration. Altered sagittal-plane gait biomechanics have been observed after ACLR, but their associations with longitudinal changes in MTFJ cartilage T1ρ and T2 remain unclear. Hypothesis/Purpose: To examine whether the peak knee flexion moment (KFM), knee flexion angle (KFA), and vertical ground-reaction force (vGRF) during gait are associated with prospective changes in medial tibiofemoral cartilage T1ρ and T2 in ACL-reconstructed knees and to compare these gait characteristics between patients undergoing ACLR and healthy control participants. We hypothesized that a higher KFM, KFA, and vGRF would be associated with greater increases in cartilage relaxation times and that patients undergoing ACLR would demonstrate altered gait characteristics compared with healthy controls.

STUDY DESIGN: Controlled laboratory study.

METHODS: Thirty-three patients undergoing ACLR underwent gait analysis before and 6 months and 1 year after ACLR and knee magnetic resonance imaging (MRI) before and 6 months, 1 year, and 2 years after ACLR. Twelve healthy controls underwent knee MRI and gait analysis at baseline and 1 year. Cartilage T1ρ and T2 were calculated for the medial tibia and medial femoral condyle. Linear regressions were used to evaluate associations between gait characteristics and changes in cartilage relaxation times from before ACLR to follow-up time points. Independent t tests were used to compare differences in gait between patients undergoing ACLR and control participants.

RESULTS: A higher KFM and KFA before ACLR were related to greater increases in medial femoral condyle T1ρ and T2 at 6 months after ACLR. Similarly, a higher KFM, KFA, and vGRF at 6 months were associated with greater increases in medial tibia and medial femoral condyle T1ρ and T2 at 1 and 2 years after ACLR. Gait characteristics at 1 year were not associated with changes in cartilage relaxation times at 2 years after ACLR. Compared with healthy controls, patients undergoing ACLR demonstrated a lower KFM at 6 months after ACLR.

CONCLUSION/CLINICAL RELEVANCE: The findings of this study revealed that a higher KFM, KFA, and vGRF during gait, especially at 6 months after ACLR, were associated with greater deterioration of MTFJ cartilage health at later time points.