Background: Lower limb malalignment increases the risk of unicompartmental knee osteoarthritis (KOA). This study investigates the association between knee cartilage quality, assessed via MRI-based T2 mapping, and lower limb malalignment. It also examines whether cartilage quality is more influenced by bony or intra-articular malalignment. Methods: In this cross-sectional analysis of 156 knees from the IMI-APPROACH cohort, tibiofemoral cartilage T2 values were measured using high-resolution MRI, distinguishing superficial and deep layers. Malalignment was categorized into entire leg, bony, and intra-articular malalignment (via the Joint Line Convergence Angle). Correlations between T2 values and alignment were assessed using Spearman's rho. A subgroup analysis evaluated cartilage quality in constitutional malalignment (malalignment without intra-articular deviation). Results: Cartilage T2 values were significantly associated with alignment. Varus knees showed significantly longer T2 in the superficial medial cartilage (ρ = –0.2, p = 0.04), and valgus knees in the lateral compartment (ρ = 0.1, p = 0.35). Associations were strongest for intra-articular malalignment (ρ = 0.3, p < 0.01). In constitutional varus, a non-significant medial T2 prolongation was observed (ρ = –0.2, p = 0.28); no changes were found in constitutional valgus. Conclusion: Lower limb malalignment, particularly intra-articular malalignment, is associated with compartment-specific lower cartilage quality, as reflected by longer T2 values. Distinguishing between bony and intra-articular malalignment, rather than overall limb alignment, should be a focus of future studies on malalignment. Future research should explore whether constitutional malalignment and early cartilage alterations may trigger cartilage degeneration and KOA progression.

Background and purpose — It is unknown whether different trajectories of pain or function are associated with timing of total hip or knee arthroplasty (THA/TKA) in osteoarthritis (OA) patients. We investigated this association in early symptomatic OA patients. Patients and methods — Data from the prospective Dutch CHECK cohort (patients with early hip/knee OA complaints) covering 9 years of follow-up were used. Pain and function were measured annually using the WOMAC questionnaires. Changes in pain/function over time were estimated using a linear mixed model adjusted for baseline age, sex, BMI, maximal Kellgren and Lawrence score, number of painful joints, and comorbidities. The same covariates were included in a Cox regression model, with time to first arthroplasty as event. Both were combined in a joint model to assess the association between changes in pain/function and time to arthroplasty. Results — Of the 868 eligible patients, 84 received a TKA/THA during follow-up. Patients receiving arthroplasty were somewhat older, had a higher Kellgren and Lawrence score and worse WOMAC scores at baseline. Irrespective of receiving arthroplasty, about two-thirds of the patients showed at least 1 period of deterioration of pain/function (≥ 10 points WOMAC subscale). In approximately two fifths this deterioration was followed by another deterioration in the following year. Worse pain and function levels increased the hazard of receiving THA/TKA (1.08 [95% CI 1.06–1.10] for pain and 1.07 [CI 1.05–1.08] for function). Changes in pain or function over time were not associated with timing of THA/TKA Interpretation — Worse pain and function levels rather than long-term changes are associated with timing of THA/TKA.