Lying VMO strengthening is a knee exercise for the thigh muscle at the front of the knee (quadriceps), including its lowest inner part just above the kneecap (vastus medialis oblique, or VMO). You lie on your back with a foam roller under one knee, straighten that knee fully, then lift the straight leg and hold it before lowering. It links two early knee rehab moves, a short arc quad and a straight leg raise, into one.

How to do the lying vmo strengthening

Lie face up on a firm bed or mat and bend one knee, with that foot flat. Lay a foam roller lengthwise under the thigh of the leg you are working, as in the video, so the knee rests over its end slightly bent with the heel down. A firm rolled towel under the knee works too.
Pull your toes up toward you and tighten the front of that thigh. Press the back of the thigh down into the roller.
Keep the squeeze on and straighten the knee all the way. The heel lifts, but the thigh stays on the roller.
With the knee held straight, lift the whole leg off the roller until it lines up with the thigh of your bent leg, as the video shows. Hold, and keep breathing steadily.
Lower the straight leg back onto the roller, then let the knee bend and the heel settle on the bed. Relax fully before the next one.

What you should feel

Work in the front of the thigh, often easiest to notice just above and to the inside of the kneecap once the knee is fully straight. The front of the hip works too while the leg is up.

Common mistakes

Lifting the leg before the knee is fully straight, so it comes up with a bend in it.
Arching the lower back as the leg rises. The bent knee on the other side helps you avoid this.
Letting the leg drop back onto the roller instead of lowering it.
Holding your breath while you hold the leg up.

How often

Many programs start with 1 to 3 sets of 8 to 12 on the working leg, holding each lift for about 5 to 10 seconds, once or twice a day. After knee surgery, the plan from your surgeon and physio comes first. Your physio will adjust this.

Stop and check with your physio if

Knee pain climbs sharply during the set, or the knee is clearly more swollen afterward.
Your lower back starts to hurt as the leg lifts.
Sharp pain in the front of the hip or groin as the leg comes up.
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.
Your wound becomes more red, hot, swollen or painful, or starts to leak. Contact your medical team the same day.

From the clinic

The voice guide describes only the first part of this exercise: pressing the knee down into a towel roll and holding the squeeze. The video goes on from there, straightening the knee over the roller and then raising the straight leg, and the steps above follow the video. If the knee starts to bend as the leg comes up, leave out the lift for now and practice the straightening part on its own, which is the short arc quad. The simplest starting point of all is the quad set, and the full lift from a flat leg is the straight leg raise.

The VMO is the bulge you can feel just above and inside the kneecap when you tighten your thigh. Whether any exercise can work it separately from the rest of the quadriceps is debated, so treat this as work for the whole thigh muscle with the knee fully straight.

After a knee fracture or knee surgery, including a knee replacement, follow your surgeon's or physio's plan, and start this exercise only when they have cleared you. Take the roller away when you finish, and rest with the leg flat rather than propped bent over it, so a stiff knee does not settle into a bent position. If you have high blood pressure, breathe steadily through every hold and never hold your breath. If you are pregnant and past the first three months, check with your physio before exercising flat on your back.

Written and checked by the PocketPhysio editorial team. Last updated 2026-09-28.

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.

Lying VMO strengthening