ObjectiveTest the hypothesis that greater baseline peak external knee adduction moment (KAM), KAM impulse, and peak external knee flexion moment (KFM) during the stance phase of gait are associated with baseline-to-2-year medial tibiofemoral cartilage damage and bone marrow lesion progression, and cartilage thickness loss.MethodsParticipants all had knee OA in at least one knee. Baseline peak KAM, KAM impulse, and peak KFM (normalized to body weight and height) were captured and computed using a motion analysis system and 6 force plates. Participants underwent MRI of both knees at baseline and two years later. To assess the association between baseline moments and baseline-to-2-year semiquantitative cartilage damage and bone marrow lesion progression and quantitative cartilage thickness loss, we used logistic regression with generalized estimating equations (GEE), adjusting for gait speed, age, gender, disease severity, knee pain severity, and medication use.ResultsThe sample consisted of 391 knees (204 persons): mean age 64.2 years (SD 10.0); BMI 28.4 kg/m2 (5.7); 156 (76.5%) women. Greater baseline peak KAM and KAM impulse were each associated with worsening of medial bone marrow lesions, but not cartilage damage. Higher baseline KAM impulse was associated with 2-year medial cartilage thickness loss assessed both as % loss and as a threshold of loss, whereas peak KAM was related only to % loss. There was no relationship between baseline peak KFM and any medial disease progression outcome measures.ConclusionFindings support targeting KAM parameters in an effort to delay medial OA disease progression.

Objective Varus and valgus alignment are associated with progression of knee osteoarthritis, but their role in incident disease is less certain. Radiographic measures of incident knee osteoarthritis may be capturing early progression rather than disease development. We tested the hypothesis: in knees with normal cartilage morphology by MRI, varus is associated with incident medial cartilage damage and valgus with incident lateral damage. Methods In MOST, a prospective study of persons at risk for or with knee osteoarthritis, baseline full-limb x-rays and baseline and 30-month MRIs were acquired. In knees with normal baseline cartilage morphology in all tibiofemoral subregions, we used logistic regression with GEE to examine the association between alignment and incident cartilage damage adjusting for age, gender, BMI, laxity, meniscal tear, and extrusion. Results Of 1881 knees, 293 from 256 persons met criteria. Varus vs. non-varus was associated with incident medial damage (adjusted OR 3.59, 95% CI: 1.59, 8.10), as was varus vs. neutral, with evidence of a dose effect (adjusted OR 1.38/1° varus, 95% CI: 1.19, 1.59). Findings held even excluding knees with medial meniscal damage. Valgus was not associated with incident lateral damage. Varus and valgus were associated with a reduced risk of incident lateral and medial damage, respectively. Conclusion In knees with normal cartilage morphology, varus was associated with incident cartilage damage in the medial compartment, and varus and valgus with a reduced risk of incident damage in the less loaded compartment. These results support that varus increases the risk for initial development of knee osteoarthritis.

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Objective Little is known about early knee osteoarthritis (OA). The significance of MRI lesions in older persons without radiographic OA is unclear. Our objectives were to determine extent of tissue pathology by MRI and evaluate its significance by testing the hypotheses: cartilage damage, bone marrow lesions (BMLs), and meniscal damage are associated with prevalent frequent knee symptoms and incident persistent symptoms; BMLs and meniscal damage are associated with incident tibiofemoral cartilage damage; BMLs are associated with incident patellofemoral cartilage damage. Methods In a cohort study of 849 OAI (Osteoarthritis Initiative) participants who had bilateral K/L 0, we assessed cartilage, BMLs, and meniscal damage using MOAKS, as well as prevalent frequent knee symptoms, incident persistent symptoms, and incident cartilage damage. Multiple logistic regression (one knee/person) was used to evaluate associations between MRI lesions and each of these outcomes. Results 76% had cartilage damage, 61% BMLs, 21% meniscal tears, and 14% meniscal extrusion. Cartilage damage (any; tibiofemoral and patellofemoral), BMLs (any; tibiofemoral and patellofemoral), meniscal extrusion, and BMI were associated with prevalent frequent symptoms. Cartilage damage (isolated patellofemoral; tibiofemoral and patellofemoral), BMLs (any; isolated patellofemoral; tibiofemoral and patellofemoral), meniscal tears, and BMI were associated with incident persistent symptoms. Hand OA but no individual lesion type was associated with incident tibiofemoral cartilage damage, and BMLs (any; any patellofemoral) with incident patellofemoral damage. Having more lesion types was associated with a greater risk of outcomes. Conclusions MRI-detected lesions are not incidental and may represent early disease in persons at higher risk for knee OA.

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