Quad sets (towel under knee)
A quad set means tightening the thigh muscle while the knee barely moves. It is one of the first exercises after a knee injury or surgery, because it gets the thigh muscle (quadriceps) working again.
How to do the quad sets (towel under knee)
- Lie on your back with both legs straight. Put a small rolled towel under the knee of the leg you are exercising.
- Let your heel rest on the bed and keep your toes pointing up toward the ceiling.
- Tighten the muscle on the front of your thigh and press the back of your knee down into the towel. Keep the rest of your body still.
- Hold for about 5 seconds and breathe normally.
- Relax fully, then repeat.
What you should feel
The front of the thigh going firm. Put your fingers on the muscle just above the kneecap on the inside to feel it switch on.
Common mistakes
- Holding your breath.
- Squeezing the buttocks instead of the thigh.
- Not relaxing fully between reps.
How often
In early rehab, often 10 reps with a 5 to 10 second hold, several times a day. Your physio will adjust this, and after surgery you follow the plan from your surgeon and physio.
Stop and check with your physio if
- Your knee pain goes up sharply.
- Your calf or thigh is getting more swollen, or becomes warm, tender, red or darker than usual, or has a new throbbing or cramping pain. This can be a blood clot, especially after an operation, an injury, time in a cast, boot or brace, or a spell of being much less mobile than usual, and after an operation it can also be an infection. Stop and contact your medical team or get medical advice the same day. If you are also short of breath or have chest pain, call emergency services.
From the clinic
This one is small and a bit dull, and patients often skip it. Do it anyway. A quadriceps that will not switch on makes every later knee exercise harder.
Take the towel out when you finish. After knee surgery, do not rest for long with a pillow or roll under the knee, because the knee can stiffen in a bent position.
Written and checked by the PocketPhysio editorial team. Last updated 2026-09-26.
This page is general education, not a diagnosis or a personal treatment plan. If you have pain, an injury or a health condition, see a physiotherapist or doctor before starting new exercises.
