Bone marrow lesion is associated with disability for activities of daily living in patients with early stage knee osteoarthritis.

Osteoarthritis of the knee (knee OA) induces pain, loss of mobility and diminished activities of daily living (ADL). Although an understanding of the pathophysiology of early stage knee OA has been developed, the structural changes associated with disability for ADL in early stage knee OA are still unclear. The aim of the present study was to examine magnetic resonance imaging (MRI)-detected changes associated with disability for ADL in patients with early stage knee OA. One hundred and thirty-two patients with early stage medial knee OA (Kellgren-Lawrence grade ≤ 2) who first visited the outpatient clinic at our university hospital were included. They were also examined by 3.0-Tesla knee MRI. The OA-associated structural changes were scored using the Whole-Organ Magnetic Resonance Imaging Score (WORMS), and clinical manifestations were evaluated by the Japanese Knee Osteoarthritis Measure (JKOM). Median quartile regression was used for the analysis. Cartilage lesion, subchondral bone attrition and osteophytes were observed in all patients. Bone marrow lesions (BMLs) and synovitis were observed in 60% and 55% of the patients, respectively. Subchondral cysts and ligament changes were observed in 6% and 17% of the patients, respectively. Pain severity of the patients was associated with medial cartilage lesions (coefficient 2.50, 95% confidence interval 0.61-4.40, p < 0.01). Disability for ADL of the patients was associated with BMLs in the medial side of the knee joint (0.82, 0.21-1.02, p = 0.04). BMLs in the medial side of the knee joint were associated with disability for ADL of patients with early stage medial knee OA.