ABSTRACT Introduction Aberrant gait variability has been observed after anterior cruciate ligament reconstruction (ACLR), yet it remains unknown if gait variability is associated 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 relaxation times and gait variability. Methods T1ρ magnetic resonance imaging and gait kinematics were collected in 22 ACLR participants (13 women; 21 ± 4 yr 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 weight-bearing portions of the medial and lateral condyles. Mean T1ρ relaxation times were extracted from each region and interlimb ratios (ILR) were calculated (i.e., ACLR/uninjured limb). Greater T1ρ ILR values were interpreted as less proteoglycan density (worse cartilage composition) in the injured limb compared with the uninjured limb. Knee kinematics were collected at a self-selected comfortable walking speed on a treadmill with an eight-camera three-dimensional 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 was associated with greater mean T1ρ ILR in the anterior lateral (r = −0.44, P = 0.04) and anterior medial condyles (r = −0.47, P = 0.03). Lesser sagittal plane KVstructure was associated with greater mean T1ρ ILR in the anterior lateral condyle (r = −0.47, P = 0.03). 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 that less knee kinematic variability structure is a mechanism linking aberrant gait to early osteoarthritis development.

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.