Knee osteoarthritis (OA) is a multifactorial disease that is affected by mechanical factors. The aim of present study was to investigate the association between multiple mechanical factors and medial knee OA in a large epidemiological cohort.
Six hundred and ninety-nine subjects (323 males and 376 females), participating in the Matsudai Knee Osteoarthritis Survey 2010, were included. Twelve mechanical factors were selected and their association with the radiographic grade of knee OA, the Western Ontario and McMaster University Index (WOMAC) pain score, and the WOMAC function score was evaluated.
A logistic regression analysis identified varus thrust to be associated with the radiographic grade of knee OA in males (OR: 1.876, 95% CI: 1.332-2.663) and females (2.61, 1.922-3.542), the WOMAC pain score in males (1.997, 1.463-2.672), and the WOMAC function score in females (1.449, 1.12-1.874). Quadriceps muscle strength was associated with the radiographic OA grade in males (0.605, 0.399-0.917) and females (0.636, 0.469-0.863), the WOMAC pain score in females (0.537, 0.445-0.789), and the WOMAC function score in males (0.581, 0.44-0.766). The knee flexion angle was also associated with the radiographic OA grade in males (0.344, 0.19-0.621) and females (0.121, 0.022-0.653), and the WOMAC pain score in males (0.287, 0.156-0.53) and females (0.537, 0.336-0.859). Obesity was associated with the radiographic OA grade in males (1.543, 1.041-2.287) and females (1.589, 1.176-2.146), the WOMAC pain score in female (2.017, 1.517-2.68). Femolo-tibial angle had no significant association with the radiographic knee OA grade or with the WOMAC pain and function scores.
Among patients with medial knee OA, dynamic mechanical factors, such as varus thrust, quadriceps muscle strength, and range of motion were more likely to be associated with the radiographic grade of knee OA and to be the WOMAC pain and function scores, compared to static mechanical factors.