Bodybuilders’ Trick Helps Knee OA Patients in Trial

A technique now widely used in sports medicine to speed recovery from leg injuries helped reduce symptoms and improve function in people with osteoarthritis (OA) of the knee, a randomized trial showed.

Among 87 patients completing the 24-week study, adding blood flow restriction (BFR) to a low-intensity exercise regimen provided patients with an average of 9.44 more Knee OA Outcome Score (KOOS) points for pain, and similar improvements for other symptoms, activities of daily living, and quality of life, compared with an exercise-only control group, according to Erik Witvrouw, PhD, of Ghent University in Belgium, and colleagues.

Patients in the BFR group also gained 56.9 extra meters in the 6-minute walk test relative to controls, the group reported in Annals of the Rheumatic Diseases.

“Given the limited tolerance for high-intensity exercise therapy and the suboptimal results from low-intensity exercise, BFR training serves as a viable alternative to high-intensity exercise mitigating excessive loading on degenerated knee joints,” Witvrouw and colleagues concluded.

Strength training has long been recommended for knee OA patients as a means of reducing symptoms in the short term and delaying the need for joint replacement. But, as Witvrouw and colleagues observed, the degree of benefit is usually not great and many patients either refuse entirely or give it up after a short while.

BFR involves applying a restricting cuff around the upper leg to reduce blood flow. It originated in bodybuilding on the theory that it increases muscle swelling and buildup of lactic acid and other metabolites, all of which are supposed to increase muscle mass when used regularly. It then expanded to other areas of sports medicine to help athletes recover from injuries and procedures such as anterior cruciate ligament reconstruction, at a time when their load tolerance is limited.

“By significantly increasing the metabolic stimulus, BFR allows for much lower mechanical loads compared with the 70% of one repetition maximum recommended by the American College of Sports Medicine for strength increments,” Witvrouw and colleagues wrote. “Consequently, BFR might offer a suitable and more effective strength training method for patients with [knee] OA whose degenerated joints do not tolerate high-intensity exercises well.”

For their trial, the researchers randomized 120 people with symptomatic and radiographically confirmed knee OA to BFR or control in equal numbers. Their disease could not be so severe that arthroplasty was imminently necessary, and participants had to be in relatively good overall health and non-obese. There was significant attrition as the trial progressed, with 17 participants dropping out by week 12 and another 16 in the final 12 weeks.

The training regimen consisted of twice-weekly sessions focusing primarily on quadriceps strengthening through leg press and extension exercises. BFR involved applying a pressurized tourniquet around the thigh to achieve 60% vascular occlusion during exercises; it was deflated between exercises. BFR was not begun in earnest until week 3, except for having the tourniquet applied during the leg press “for familiarization,” the researchers explained. The program for both groups lasted 12 weeks, after which patients could do as they wished; they were asked to return at week 24 for a follow-up assessment.

For the initial 120, mean age was about 58 and roughly three-quarters were women. About 40% had knee OA at severity grade 2; most of the rest were at grade 3. KOOS scores at baseline averaged approximately 60 for pain, 55 for other symptoms, and 37 for quality of life, all out of a possible 100 points (lower scores mean greater severity).

Separation between the groups was apparent at week 6 and increased as the study went on. Patients in the control group generally showed some improvement initially but plateaued after week 12. On the other hand, improvement in the three major domains (pain, other symptoms, and quality of life) continued for the BFR group through the study’s end at week 24.

Mean differences between the two groups at week 24, all favoring BFR, were as follows:

• KOOS pain: 9.44 points (P=0.0008)
• KOOS other symptoms: 9.03 points (P=0.0004)
• KOOS activities of daily living: 6.95 points (P=0.0144)
• KOOS sport: 7.49 points (P=0.1296)
• KOOS quality of life: 13.23 points (P=0.0001)

Significant improvements with BFR relative to control were seen in other outcome measures as well, including 30-second knee bend and chair-to-stand tests, fast-pace walking, and stair climbs. For most outcomes, the researchers indicated, effect sizes were “moderate to large” after the 12-week program and these “persisted and [were] even enhanced” after the additional 12 weeks of follow-up.

Limitations to the study included its open-label design (although participants weren’t told what hypothesis was being tested); its exclusion of patients with common comorbidities such as obesity, severe hypertension, and type 2 diabetes; and the substantial dropout rate.

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