Heel Prop for Knee Straightening
Talk to your doctor first. General education, not medical advice.This content is general education, not medical advice, diagnosis or treatment. Get approval from your physician or another qualified healthcare provider before starting any exercise program, especially if you have a medical condition, a recent injury or surgery, are pregnant, or take medication. Stop and seek medical advice if an exercise causes pain, dizziness, chest discomfort or shortness of breath. You choose to exercise at your own risk. Read the full medical disclaimer.
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ACL injury exercisesMCL sprain exercisesExercises after ACL reconstruction
Why it helps
Being able to straighten the knee fully matters for walking normally. A knee that stays slightly bent makes the thigh work harder and can cause a limp.
After knee surgery or injury, it is easy to keep a pillow under the knee for comfort, which can make it stiffen in a bent position. The heel prop does the opposite: a slow, gentle stretch into straightening.
Step-by-Step Instructions
- Lie on your back or sit with the leg out straight on a bed or sofa.
- Place a rolled towel or small pillow under the heel so the calf and the back of the knee are off the surface.
- Relax the thigh and let the knee sink toward straight.
- Every minute or so, gently tighten the thigh muscle to push the back of the knee down (a quad set), then relax again.
- Stay for 5 to 10 minutes, or as long as advised.
Key Form Cues
- Nothing under the knee: The knee must be unsupported.
- Toes up: Keep the foot pointing to the ceiling.
- Relax: Let the leg go heavy.
How much to do
5 to 10 minutes, 3 to 4 times a day, unless your surgeon or physical therapist gives a different plan.
Progression & Regression
Regression (Make It Easier)
- Use a lower towel roll
- Do it for 2 to 3 minutes at a time
- Add a pillow behind your back to sit more upright
Progression (Make It Harder)
- Stay longer, up to 15 minutes
- Add quad sets every minute
- Do it after heel slides to work both directions
Who it suits, and who should check first
Good fit for: people regaining knee straightening after knee replacement, ACL reconstruction or knee injury.
Check with your clinician first if: your surgeon has given restrictions on knee straightening, or you have a new or increasing swelling, redness or calf pain.
Precautions
Follow your surgical team’s plan.
- A stretching ache behind the knee is expected; it should ease when you stop.
- Ice afterward may help if your team allows it.
- Do not add heavy weights to the knee unless advised.
- Stop and consult your provider if: you get sharp pain, calf pain or swelling, fever, or the wound looks red or leaks.
Frequently asked questions
Why can’t I straighten my knee after surgery?
Swelling, pain and protective muscle tension keep the knee bent. Gentle, regular stretching like the heel prop helps restore it.
Should I put a pillow under my knee?
Most surgical teams advise against keeping a pillow under the knee for long periods after knee replacement, because it can make the knee stiffen in a bent position.
Heel prop or prone hang?
Both use gravity to straighten the knee. The heel prop is done lying on your back; the prone hang is lying face down with the lower leg off the bed.
Video: Concord Hospital Health System on YouTube. We link to it because it shows the movement clearly; the written instructions and dosing on this page are our own general guidance.
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