Functional Outcomes After Bilateral Versus Unilateral Total Knee Arthroplasty: A Retrospective Cohort Study in Saudi Arabia

Background: Osteoarthritis (OA) is a chronic degenerative joint disease that often leads to pain, stiffness, and functional disability. Total Knee Arthroplasty (TKA) remains the most effective surgical treatment for end-stage OA. This study aimed to compare the clinical and functional outcomes of patients undergoing unilateral and bilateral TKA in a tertiary rehabilitation setting in Saudi Arabia. Methods: This retrospective cohort study included 265 patients (≥35 years; both sexes) who underwent primary TKA at Sultan Bin Abdualziz Humanitartian City (SBAHC) Between 2016 and 2020. Clinical and functional data—including pain intensity (Visual Analog Scale), range of motion (goniometric assessment), muscle strength (Manual Muscle Testing), and functional independence (Functional Independence Measure, FIM)—were extracted from medical records at three time points: preoperatively, before discharge, and 3–6 months post-discharge. Results: The mean age of the patients was 67.1 ± 8.0 years, with females comprising 66.8%. Postoperatively, there was a significant reduction in pain scores (p < 0.001) and improvement in knee flexion and extension (p < 0.001). Muscle strength and FIM scores improved significantly across all patients, irrespective of age, gender, or postoperative complications. The percentage improvement in total FIM was greater in unilateral TKA patients (63.9%) compared with bilateral TKA patients (48.7%). Conclusions: Both unilateral and bilateral TKA patients demonstrated significant improvements in pain, joint mobility, muscle strength, and functional independence following a high-intensity rehabilitation program, with greater functional gains observed among unilateral TKA patients.