Blood Flow Restriction induces hypoalgesia in recreationally active adult male anterior knee pain patients allowing therapeutic exercise loading

Objective: To evaluate if a single blood flow restriction (BFR)-exercise bout would induce hypoalgaesia in patients with anterior knee pain (AKP) and allow painless application of therapeutic exercise.

Design: Cross-sectional repeated measures design.

Setting: Institutional out-patients physiotherapy clinic.

Patients: Convenience sample of 30 AKP patients.

Intervention: BFR was applied at 80% of complete vascular occlusion. Four sets of low-load open kinetic chain knee extensions were implemented using a pain monitoring model.

Main outcome measurements: Pain (0-10) was assessed immediately after BFR application and after a physiotherapy session (45 min) during shallow and deep single-leg squat (SSLS, DSLS), and step-down test (SDT). To estimate the patient rating of clinical effectiveness, previously described thresholds for pain change (≥40%) were used, with appropriate adjustments for baseline pain levels.

Results: Significant effects were found with greater pain relief immediate after BFR in SSLS (d = 0.61, p < 0.001), DSLS (d = 0.61, p < 0.001), and SDT (d = 0.60, p < 0.001). Time analysis revealed that pain reduction was sustained after the physiotherapy session for all tests (d_(SSLS) = 0.60, d_(DSLS) = 0.60, d_(SDT) = 0.58, all p < 0.001). The reduction in pain effect size was found to be clinically significant in both post-BFR assessments.

Conclusion: A single BFR-exercise bout immediately reduced AKP with the effect sustained for at least 45 min.