Introduction Blood flow restriction (BFR) with low-load resistance exercise (LLRE) can induce significant pain reduction in anterior knee pain (AKP). This study evaluated the BFR-LLRE effect on pain compared to sham-BFR, or LLRE alone in patients with AKP.

Materials and methods 36 patients were randomly allocated to BFR, sham-BFR, or control group in this single-blinded trial. Pain was assessed immediately after intervention, and after a sequential physiotherapy session (45 min). BFR pressure was set to 80% of complete occlusion. All groups performed four sets of knee extensions with individualized load (≤5 kg) as indicated by a pain monitoring approach (pain ≤4/10). Outcome measures were pain (0–10) during shallow and deep single-leg squat (SLSs-SLSd), and step-down test (SDT). Data were analyzed using factorial repeated measures ANOVA and were interpreted as clinically meaningful changes (d>0.80; 30% pain reduction) and numbers needed to treat (NNT).

Results Groups did not differ at baseline. No significant between-group differences were found.

Significant within-group immediate pain reductions found only in BFR group (p≤0.003; SLSs/d=1.44, SLSd/d=1.27, SDT/d=0.94), but not in sham-BFR and control group (all p>0.05).

Following physiotherapy session, pain was sustained significantly reduced only in BFR group (p≤0.003; SLSs/d=1.71, SLSd/d=0.97, SDT/d=0.84), but not in sham-BFR and control group (all p>0.05).

NNT ranged from 2 to 4 depending on the outcome measure used.

Conclusion BFR reduces pain independent of the effect of exercise. One BFR-exercise bout immediately reduced AKP with the effect sustained for at least 45 min, an effect not seen with sham-BFR and without BFR.