Knee osteoarthritis: moderate lifting built more quad strength than passive BFR

Blood flow restriction (BFR) is often pitched to people whose knees hurt too much to lift. On strength alone, though, moderate-intensity resistance training still came out ahead for those who could tolerate it. That was the result of a single-blind randomized trial that split 75 adults aged 45–60 with knee osteoarthritis into three groups for 16 sessions over 8 weeks.

What did each group do?

• Passive BFR at 50% — thigh cuffs set to 50% of limb occlusion pressure (LOP). Passive BFR relies on the cuff stimulus rather than heavy resistance work.
• Passive BFR at 70% — the same approach at 70% of LOP.
• Moderate-intensity resistance training — ordinary resistance exercise, no cuffs.

Which approach built more quadriceps strength?

After 8 weeks, moderate training increased quadriceps torque by 18.57 N·m more than BFR at 50% and 13.81 N·m more than BFR at 70%. The trade-off was effort: perceived exertion rose in the moderate group and did not change in either BFR group. Real load still did the most for muscle strength.

So when is BFR worth using?

On lower-extremity function, BFR at 70% was best — 6.8 points better than moderate training and 15.9 points better than BFR at 50%. Every group improved on every outcome over time, and there were no between-group differences in pain intensity, osteoarthritis impact, functional mobility or self-rated improvement. Dropping the pressure to 50% clearly shrank the benefit.

How should a lifter with sore knees log this?

If knee pain has forced your squat down, keeping moderate loads you can tolerate is still the best option for quad strength. On weeks when even that is too much, 70% BFR can protect function, and once you can load up again, retest your 1RM so your big-three total reflects where you really are. Knee-friendly squat positions are covered in knee-friendly leg training, and the BFR basics in our BFR guide.