The type of osteoarthritis and the degree of severity which causes restriction of knee range of motion (ROM) is still largely unknown. The objective of this study was to analyse the location and the degree of cartilage degeneration that affect knee range of motion and the connection, if any, between femorotibial angle (FTA) and knee ROM restriction.
Four hundreds and fifty-six knees in 230 subjects with knee osteoarthritis undergoing knee arthroplasty were included. Articular surface was divided into eight sections, and cartilage degeneration was evaluated macroscopically during the operation. Cartilage degeneration was classified into four grades based on the degree of exposure of subchondral bone. A Pearson correlation was conducted between FTA and knee flexion angle to determine whether high a degree of FTA caused knee flexion restriction. A logistic regression analysis was also conducted to detect the locations and levels of cartilage degeneration causing knee flexion restriction.
No correlation was found between FTA and flexion angle (r = -0.08). Flexion angle was not restricted with increasing FTA. Logistic regression analysis showed significant correlation between restricted knee ROM and levels of knee cartilage degeneration in the patella (odds ratio (OR) = 1.77; P = 0.01), the lateral femoral condyle (OR = 1.62; P = 0.03) and the posterior medial femoral condyle (OR = 1.80; P = 0.03).
For clinical relevance, soft tissue release and osteophyte resection around the patella, lateral femoral condyle and posterior medial femoral condyle might be indicated to obtain a higher degree of knee flexion angle.