Association between knee stiffness and MRI-detected lesions: data from the osteoarthritis initiative (OAI).

objectiveTo explore the association between knee stiffness and MRI-detected lesions.

methodsA within-person knee-matched case-control study was performed. We included participants from the Osteoarthritis Initiative (OAI) whose stiffness score differed by ≥ 1 point between their knees, as assessed by the Western Ontario and McMasters Universities Osteoarthritis Index (WOMAC) stiffness subscales. We evaluated six different intra-knee structural lesions using the MRI Osteoarthritis Knee Score (MOAKS). A latent class analysis was used to identify distinct subgroups of MRI-detected lesions. Then, we conducted a conditional logistic regression model to explore the association between these subgroups and knee stiffness.

resultsOut of the 149 patients who were eligible, we categorized their knees into four subgroups based on the types of MRI-detected lesions: (I) minimal lesions, (II) mild lesions, (III) moderate lesions, and (IV) severe lesions. Compared with subgroup I, there were no significant differences in the likelihood of having greater knee stiffness at morning wake-up in subgroups II to III, while there was a significantly increased risk of greater knee stiffness in subgroup IV. Compared with subgroup I, there was no significant difference in the likelihood of having greater knee stiffness after sitting, lying, or resting in subgroup II, while there was a significantly increased risk of greater knee stiffness in subgroups III to IV.

conclusionWe found that meniscus lesions, synovitis, and effusion were associated with knee stiffness. However, neither cartilage lesions nor bone marrow lesions in the tibio-femoral or patella-femoral joints were significantly correlated with knee stiffness.