Cartilage lesions are not the main factor influencing pain and functional impairment in early knee osteoarthritis : a multivariate analysis on intra- and extra-articular factors affecting symptoms in over 200 knees.

Abstract

Aims: To investigate the correlation between symptoms, in terms of pain and functional scores, and the extent of cartilage damage as well as other intra- and extra-articular factors in patients suffering from early knee osteoarthritis (OA).

Methods: The subjects were selected from the Osteoarthritis Initiative database according to the following inclusion criteria: Kellgren-Lawrence (KL) grade 0-1-2, MRI at baseline, and availability of cartilage-denuded subchondral bone values. For each patient the following data were analyzed: demographic data, KL grade, percentage of subchondral bone denuded from cartilage, patellar quadriceps tendinitis, effusion, anserine bursa tenderness, meniscal extrusion, Hoffa body synovitis, bone marrow lesions (BML), visual analogue scale (VAS) for pain, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) total score, and WOMAC pain subscale.

Results: A total of 204 knees were included in the analysis. The multivariate analysis showed that VAS was influenced by patellar quadriceps tendinitis (p < 0.001/η2 = 0.113), anserine bursa tenderness (p = 0.009/η2 = 0.033), and percentage of cartilage-denuded subchondral bone (p = 0.032/η2 = 0.023). WOMAC was influenced by patellar quadriceps tendinitis (p < 0.001/η2 = 0.118), anserine bursa tenderness (p < 0.001/η2 = 0.060), medial meniscus extrusion (p < 0.001/η2 = 0.066), BML of the lateral compartment (p = 0.015/η2 = 0.029), patellofemoral BML (p = 0.096/η2 = 0.014), and percentage of cartilage-denuded subchondral bone (p = 0.083/η2 = 0.015). The WOMAC pain subscale was influenced by patellar quadriceps tendinitis (p < 0.001/η2 = 0.095), anserine bursa tenderness (p = 0.001/η2 = 0.055), medial meniscal extrusion (p < 0.001/η2 = 0.071), age (p = 0.032/η2 = 0.023), total BML (p = 0.001/η2 = 0.057), and percentage cartilage-denuded subchondral bone of the tibial plateau (p = 0.044/η2 = 0.020).

Conclusion: The extent of cartilage damage is not the main factor influencing pain and functional impairment in early knee OA. Other intra- and extra-articular joint OA features, including extensor mechanism tendinitis, anserine bursa tenderness, meniscal extrusion, and BMLs have greater impact in driving patient symptoms.