Effects of Blood Flow Restriction Therapy in Individuals With Knee Osteoarthritis: Overview of Systematic Reviews

Knee osteoarthritis (KOA) is frequently accompanied by quadriceps weakness. Resistance training is recommended, but high-intensity resistance training (HIRT) may be poorly tolerated in some patients, whereas low-intensity resistance training (LIRT) may yield smaller strength gains. Low-intensity blood flow restriction training (LIBFR) has been proposed as a low-load strategy to stimulate muscle adaptations; however, the evidence base has been summarized in multiple systematic reviews with variable conclusions.

To synthesize and appraise the evidence on the efficacy and safety of LIBFR in individuals with KOA through an overview of systematic reviews.

We searched MEDLINE, EMBASE, Cochrane Database, Web of Science, CINAHL, SPORTDiscus, PEDro, Epistemonikos, and gray literature (ProQuest, Global ETD) for systematic reviews of randomized clinical trials comparing LIBFR with LIRT and/or HIRT. Reviews were eligible if they evaluated supervised exercise-based LIBFR delivered ⩾2 to 3 sessions/week for ⩾4 weeks. Two reviewers independently screened, extracted data, and assessed methodological quality (AMSTAR 2). Certainty of evidence was appraised using Grading of Recommendations Assessment, Development, and Evaluation (GRADE) based on KOA-specific quantitative syntheses, applying a hierarchical approach in the presence of overlap across reviews.

Eighteen systematic reviews (57 randomized trials; 5656 participants) were included. Compared with LIRT, LIBFR was associated with greater improvements in quadriceps strength (standardized mean difference [SMD] = 0.75; 95% confidence interval [CI] = [0.40 to 1.10]) and muscle hypertrophy (SMD = 0.81; 95% CI = [0.10 to 1.52]), although certainty of evidence was very low. Compared with HIRT, LIBFR was associated with fewer adverse events (risk ratio [RR] = 0.26; 95% CI = [0.09 to 0.72]).Across comparisons, effects on pain and functional outcomes were generally similar, and between-group differences were not consistently observed.

The LIBFR may improve quadriceps strength and hypertrophy relative to LIRT and may have a more favorable adverse-event profile than HIRT, but confidence in these estimates is limited by low-/very low-certainty evidence and variability in protocols and reporting. Well-designed, longer-term randomized trials with standardized LIBFR parameters and robust safety reporting are needed to clarify patient-important outcomes.