Associations between patellofemoral joint cartilage T1ρ and T2 and knee flexion moment and impulse during gait in individuals with and without patellofemoral joint osteoarthritis

Summary Objective This study aimed to investigate the associations between patellofemoral cartilage T 1ρ and T 2 relaxation times and knee flexion moment (KFM) and KFM impulse during gait. Method Knee magnetic resonance (MR) images were obtained from 99 subjects with and without patellofemoral joint (PFJ) osteoarthritis (OA), using fast spin-echo, T 1ρ and T 2 relaxation time sequences. Patellar and trochlear cartilage relaxation times were computed for the whole cartilage, and superficial and deep layers (laminar analysis). Subjects also underwent three-dimensional (3D) gait analysis. Peak KFM and KFM impulse were calculated during the stance phase. Linear regressions were used to examine whether cartilage relaxation times were associated with knee kinetics during walking while adjusting age, sex, body mass index (BMI) and walking speed. Results Higher peak KFM and KFM impulse were significantly related to higher T 1ρ and T 2 relaxation times of the trochlear and patellar cartilage, with standardized regression coefficients ranging from 0.21 to 0.28. Laminar analysis showed that overall the superficial layer of patellofemoral cartilage showed stronger associations with knee kinetics. Subgroup analysis revealed that in subjects with PFJ OA, every standard deviation change in knee kinetics was related to greater increases in PFJ cartilage T 1ρ and T 2 (standardized coefficients: 0.29 to 0.41). Conversely, in subjects without OA, weaker relationships were observed between knee kinetics and PFJ cartilage T 1ρ and T 2 . Conclusions Our findings suggest that increased peak KFM and KFM impulse were related to worse cartilage health at the PFJ. This association is more prominent in superficial layer cartilage and cartilage with morphological lesions.