5 key exercises after total knee replacement, and how to do them

The surgery is over. Now the real work starts, mostly at home.

In the first weeks, your new knee needs to bend and to straighten fully. Your thigh muscle needs to get strong again. A handful of simple exercises does most of this work.

This guide covers the five exercises that appear again and again in hospital and surgeon guides. It also covers recovery phases, bend and straightening goals, and warning signs. Your own physiotherapist's plan always comes first.

Why early exercise matters

The NHS says that doing your exercises early on helps the long-term strength and movement in your knee.

A US clinical guideline for physiotherapists, published in 2020, recommends that physio should start within 24 hours of surgery. It also recommends ice for early pain, and strength training that starts within the first week.

The early exercises do three jobs, according to the American Academy of Orthopaedic Surgeons (AAOS). They keep blood moving in your legs to help prevent clots. They build muscle strength. They bring back knee movement.

You do not need a clinic for most of this. A 2023 review of 15 studies compared home-based rehab with outpatient rehab after knee replacement. It found home-based rehab to be an effective, safe and lower-cost option.

The five exercises

A common plan from one NHS hospital is 10 of each exercise, three times a day, in short sessions. Your physio may set different numbers. Follow theirs.

1. Ankle pumps

This one keeps blood flowing in your calf. You can start it in the recovery room.

1. Lie on your back or sit with your legs out straight.
2. Pull your toes up towards you.
3. Point your toes away from you.
4. Keep going at a steady pace.

How much: The West Hertfordshire NHS leaflet suggests 10 ankle pumps every hour. Keep going until the swelling in your ankle and lower leg has gone.

2. Quad sets (static quads)

This wakes up the big muscle on the front of your thigh. It also helps the knee straighten.

1. Lie on your back or sit with your operated leg straight.
2. Pull your ankle towards you.
3. Tighten your thigh muscle and push the back of your knee down into the bed.
4. Hold for 5 to 10 seconds.
5. Relax fully.

How much: The AAOS suggests about 10 in two minutes, a one-minute rest, then another round. Stop when your thigh feels tired.

3. Heel slides (knee bends in bed)

This is your main exercise for getting the knee to bend.

1. Lie on your back with both legs flat.
2. Slowly slide the heel of your operated leg towards your bottom. Keep the heel on the bed.
3. Bend as far as you can.
4. Hold the bend for 5 to 10 seconds.
5. Slide the heel back down until the leg is straight.

How much: 10 times, three times a day, or until your leg is tired.

Tip: Once you are sitting out in a chair, your physio may add seated knee bends. You sit with your thigh supported, bend the knee as far as you can, then hold for 5 to 10 seconds.

4. Straight leg raises

This builds strength in your thigh.

1. Lie on your back. Bend your good knee and keep that foot flat on the bed.
2. Keep your operated leg straight. Tighten your thigh, as in a quad set.
3. Lift the straight leg a few inches off the bed.
4. Hold for 5 to 10 seconds.
5. Lower it slowly.

How much: Repeat until your thigh feels tired. Keep the knee straight the whole time.

5. Short-arc quads (inner range quads)

This strengthens your thigh through the last part of straightening.

1. Lie on your back or sit with your operated leg straight.
2. Place a rolled towel under your operated knee.
3. Tighten your thigh and lift your heel off the bed until the knee is straight.
4. Keep the back of your knee resting on the towel.
5. Hold for 2 to 3 seconds, then lower slowly.

How much: 10 times, three times a day.

Important: Take the towel away when you finish. The West Hertfordshire leaflet warns that leaving your knee resting on a towel roll will stop you from getting a straight knee.

Pain rules while you exercise

Some pain, discomfort and stretching during and after your exercises is normal.

The West Hertfordshire NHS leaflet gives a simple test. If pain lasts more than about 30 minutes after an exercise, or keeps getting worse, ease off. Do the exercise less forcefully or less often. If that does not help, talk to your physiotherapist.

• Take your pain medicine before you exercise, as your doctor advised.
• Use an ice pack or frozen peas wrapped in a cloth for 10 to 15 minutes. Never put ice straight on your skin. Remove it at once if the skin turns white. If you have a circulation problem, ask your doctor first.
• Raise your leg to bring swelling down. Lying flat for an hour each morning and afternoon helps.

Goals for bending and straightening

The West Hertfordshire leaflet sets a clear goal before you leave hospital. You should be able to get a straight knee and about 90 degrees of bend. That is a right angle, like sitting on a chair.

Over the following months, your bend keeps improving. The AAOS says an average of about 115 degrees of movement is generally expected after surgery. Most people can almost fully straighten the new knee.

Straightening matters as much as bending. To protect your straight knee:

• Do not sleep with a pillow under your knee. The NHS gives this advice.
• Try the heel prop. The AAOS describes it. Place a small rolled towel just above your heel so the heel floats off the bed. Tighten your thigh and press the back of your knee towards the bed. Hold 5 to 10 seconds.

A note on floor sitting and squatting

Daily life in many Indian homes includes floor sitting, kneeling for prayer or an Indian-style toilet. These need far more knee bend than walking does.

In a study of 30 healthy Indian adults, squatting with the heels raised needed about 157 degrees of knee bend. That is well beyond the 115 degrees most new knees reach.

The NHS advises you not to kneel on the new knee until your doctor says it is safe. The AAOS says kneeling is sometimes uncomfortable but not harmful. Ask your surgeon what is right for your knee before you try any of these positions.

Early recovery phases

Everyone recovers at a different pace. These timings come from the NHS and the AAOS. Treat them as a rough guide.

In hospital (day 0 to about day 4)

• You start walking soon after surgery, with a walker or crutches.
• Most people go home 1 to 4 days after surgery.
• Goal: a straight knee, about 90 degrees of bend and safe walking with an aid.

Weeks 1 to 2 at home

• Keep up your exercises and walk a little, often. Land on your heel first, then roll through your foot.
• Stitches or clips usually come out after about 10 days.

Weeks 2 to 6

• Many people move from a walker to a single stick around 2 to 3 weeks. The AAOS says you are ready when you can stand and walk for more than 10 minutes without leaning on the walker.
• Hold the stick in the hand opposite your operated knee.
• On stairs, use the handrail. Go up with your good leg first. Come down with your operated leg first.
• From about 4 to 6 weeks, your physio may add light ankle weights or an exercise bike.

About 6 weeks onwards

• The NHS says you can try walking without an aid from about 6 weeks, if you feel ready.
• Wait at least 6 weeks before driving after a total knee replacement. Check with your doctor first.
• Most people return to work at around 6 to 12 weeks, depending on the job.
• Avoid heavy housework, such as carrying heavy shopping, for the first 3 months.

Full recovery can take several months or longer. Keep doing your exercises until your physio tells you to stop.

When to call your surgeon or physiotherapist

Most people recover without complications. Still, know these warning signs from the NHS and the AAOS.

Call your surgeon or doctor urgently if you notice signs of infection:

• A fever that does not go away (higher than 100°F, about 37.8°C)
• Chills, or feeling hot and shivery
• Fluid or pus coming from the wound
• Redness, swelling, tenderness or pain in the knee that is getting worse instead of better

Call your doctor urgently if you notice signs of a blood clot in your leg:

• New or increasing pain in your calf, or a throbbing or cramping pain
• New or increasing swelling in your calf, ankle or foot

Call an ambulance (112 in India) or go to the emergency department straight away if you have:

• Sudden shortness of breath
• Sudden chest pain

These can be signs of a clot in the lung. Do not drive yourself to hospital.

Talk to your physiotherapist if:

• Your knee is not bending or straightening as expected
• Pain and stiffness are not improving
• Your knee feels unstable when you stand or walk

Doing your exercises at home

Doing the same exercises every day, alone, it is hard to know if you are doing them right. FiixBE can help. Your physiotherapist writes your plan. Your phone camera counts your reps, measures your knee angle and flags form mistakes as you go. Each session goes back to your physio. You can try it on the web today.