Abstract: OBJECTIVE: There is no consensus on which sit-up strategy to adopt in knee osteoarthritis patients of different ages. Therefore, this study evaluated the biomechanical characteristics of sit-ups in knee osteoarthritis patients of different ages compared with healthy individuals by meta-analysis system and analyzed the sit-up movement patterns of patients of different ages to provide a reference for improving the sit-up function of patients.
METHODS: By March 2023, observational studies of biomechanical characteristics of sitting up in patients with knee osteoarthritis and healthy population were retrieved on PubMed, Web of Science and CNKI. Subjects were required to be patients over 50 years of age with knee osteoarthritis who had Kellgren-Lawrence severity grading ≥I on knee imaging and who had regular knee pain. Subjects were analyzed by age (50-60 years vs. over 60 years) and severity (mild to moderate patients vs. severe patients) subgroups according to inclusion and exclusion criteria. Quality assessment was performed using the modified Down and black scale. Stata 16.0 software was used to perform subgroup analysis to determine the biomechanical characteristics of sitting up in patients with knee osteoarthritis of different ages and severities.
RESULTS: A total of 14 randomized controlled trials (824 subjects) were included in the meta-analysis. The mean quality score of all included literature was 76.2, with a range of 66.7 to 86.7, all of which were of medium to high quality and representative. The included studies were of moderate to high quality and representative. Meta-analysis results found that (1) compared to healthy individuals, patients with knee osteoarthritis had longer total sitting up time (SMD=0.92, 95%CI:0.76-1.09), P < 0.001) and longer extension phase time (SMD=0.46, 95%CI:0.18-0.74, P=0.001). Compared to mild to moderate patients, the total duration increased more significantly in severe patients (P < 0.001) and the duration of the extension phase increased more significantly in patients over 60 years of age than in patients 50-60 years of age (P=0.001). (2) Compared to healthy individuals, patients with knee osteoarthritis had greater sitting-up trunk flexion motion range (SMD=0.64, 95%CI:0.37-0.91, P < 0.001); knee flexion motion range (SMD=-0.47, 95%CI: -0.70 to -0.24, P < 0.001) and ankle dorsiflexion motion range (SMD=-0.32, 95%CI:-0.56 to -0.08, P=0.01) were smaller. And knee flexion motion range decreased more significantly in patients over 60 years of age than in patients 50-60 years of age (P < 0.001). (3) The peak hip flexion moment (SMD=-0.57, 95%CI:-0.83 to -0.31, P < 0.001) and peak knee extension moment (SMD=-0.83, 95%CI:-1.08 to -0.59, P < 0.001) were smaller in patients with knee osteoarthritis.
CONCLUSION: (1) Patients with knee osteoarthritis over the age of 60 years have a longer sit-up cushion and extension phase than patients aged 50 to 60 years. The increase in total sit-up duration was also more pronounced in patients with higher severity grades. The increased length of sitting up in patients with advanced age and knee osteoarthritis severity may increase the duration of cartilage loading, exacerbate knee pain symptoms, and increase the difficulty of sitting up in this population. (2) Patients with knee osteoarthritis exhibit limited knee and ankle flexion motion range. Knee mobility is more limited in patients over 60 years of age. (3) Patients with knee osteoarthritis have reduced peak hip flexion and knee extension moments, which may be a compensatory strategy for pain relief.

Key words: knee osteoarthritis, degeneration of knee soft tissue, age, severity, sit to stand, kinematics, kinetics, peak knee extension moment, peak knee inversion moment, meta-analysis