Influencing factors of flexion contracture among patients with knee osteoarthritis: a multi-center retrospective cross-sectional study

Knee osteoarthritis (KOA) is a chronic disease with a high prevalence and disability rate. Alterations in lower limb alignment and reduction in lower limb muscle strength are important factors in the progression of KOA. Although pain is the main reason for KOA patients to seek medical treatment, the presence or absence of joint deformity is one of the crucial factors influencing the prognosis and recurrence of the disease. Approximately half of KOA patients may become disabled due to the development of joint deformity. To investigate the prevalence, characteristics, and influencing factors of knee flexion contracture in patients with KOA, providing a basis for preventing and delaying the occurrence of knee joint deformities in such patients. From January 2022 to June 2022, a survey was conducted on 870 patients with KOA visiting 7 community hospitals. Patients whose knees could fully extend to 0° were categorized as the none flexion contracture (NFC) Group, while those whose knees could not fully extend to 0° were categorized as the flexion contracture (FC) Group. Data were collected on patients' demographic characteristics, work and lifestyle habits, dietary preferences, and clinical evaluations. Compare the results of the two groups, and perform a Logistic regression analysis on the influencing factors that show differences to identify the risk factors and protective factors for joint deformity. A total of 853 patients with KOA were included in the study, with a questionnaire recovery rate of 98.05%. Among them, 308 patients were in the FC Group, with a prevalence of knee flexion contracture at 36.11%, and 545 patients were in the NFC Group. The risk factors (OR > 1) included being female, older age, higher Body Mass Index (BMI), history of knee trauma, history of osteoporosis, physically demanding occupations, living in high-rise buildings without elevators, squatting posture during defecation, disease duration, and Kellgren-Lawrence (KL) III-IV grade. Protective factors (OR < 1) included commuting by cycling or driving, regular knee exercises, and calcium supplementation. Standing occupational posture, mountain climbing or hiking activities, and KL II grade were not associated with the occurrence of joint deformity (P > 0.05). Among patients with KOA, KL III-IV grade, living in high-rise buildings without elevators, history of knee injury, and squatting posture during defecation were identified as risk factors for knee joint deformity, which should be prevented early to delay joint deformity.