Efficacy of Active Exercises to Improve Range of Motion in Knee Joint After Total Knee Arthroplasty. A Randomized Controlled Trial

Background and Purpose
After total knee arthroplasty (TKA), not everybody gains a sufficient joint mobility. The objective of this study was to investigate the effects of high-frequency (HF) versus low-frequency (LF) self-managed knee flexion exercises in individuals with reduced flexion after a TKA.

Methods
The study was a randomized controlled trial in adults with a TKA within 6 to 26 weeks and knee flexion ≤ 105° who participated in an 18-day inpatient rehabilitation program. Patients were randomized to additional self-managed HF (eight flexion and extension exercises per day) versus LF (two flexion and extension exercises per day). The primary outcome was knee flexion change. Secondary outcomes were changes of knee extension, Six-Minute Walk Test, 30 Second Chair-Stand Test, pain using Numeric Rating Scale, and Knee Injury and Osteoarthritis Outcome Score.

Results
The participants (n = 83) were 65 (SD 8.8) years old and 70% were women. The HF (n = 44) and LF (n = 39) groups performed knee flexions 5.3 (1.4) and 1.7 (0.3) times/day, respectively. The flexion increased 14.2 [11.6; 16.7]° with HF versus 10.1 [8.6; 11.6]° with LF, with 4.1° difference between groups (p = 0.007). Secondary outcomes increased in the two groups without differences between the groups.

Discussion
In individuals with reduced joint mobility after TKA, HF self-managed knee flexion exercises were associated with a positive change in flexion compared with LF, though the between-group difference was smaller than expected.

Trail Registration
The study was registered on ClinicalTrials.gov (NCT06188091)