Gait Variability Structure Linked to Worse Cartilage Composition Post-ACL Reconstruction.

INTRODUCTION: Aberrant gait variability has been observed following anterior cruciate ligament reconstruction (ACLR), yet it remains unknown if gait variability associates with early changes in cartilage composition linked to osteoarthritis development. Our purpose was to determine the association between femoral articular cartilage T1ρ magnetic resonance imaging (MRI) relaxation times and gait variability.

METHODS: T1ρ MRI and gait kinematics were collected in 22 ACLR participants (13 Females; 21 ± 4 years old; 7.52 ± 1.43 months post-ACLR). Femoral articular cartilage from the ACLR and uninjured limbs were segmented into anterior, central, and posterior regions from the weightbearing portions of the medial and lateral condyles. Mean T1ρ relaxation times were extracted from each region and interlimb ratios (ILRs) were calculated (i.e., ACLR/uninjured limb). Greater T1ρ ILRs were interpreted as less proteoglycan density (worse cartilage composition) in the injured limb compared to the uninjured limb. Knee kinematics were collected at a self-selected comfortable walking speed on a treadmill with an 8-camera 3D motion capture system. Frontal and sagittal plane kinematics were extracted, and sample entropy was used to calculate kinematic variability structure (KVstructure). Pearson's product-moment correlations were conducted to determine the associations between T1ρ and KVstructure variables.

RESULTS: Lesser frontal plane KVstructure associated with greater mean T1ρ ILR in the anterior lateral (r = -0.44, p = .04) and anterior medial condyles (r = -0.47, p = .03). Lesser sagittal plane KVstructure associated with greater mean T1ρ ILR in the anterior lateral condyle (r = -0.47, p = .03).

CONCLUSIONS: The association between less KVstructure and worse femoral articular cartilage proteoglycan density suggests a link between less variable knee kinematics and deleterious changes joint tissue changes. The findings suggest less knee kinematic variability structure is a mechanism linking aberrant gait to early osteoarthritis development.