Key Takeaways
- Recovery happens in phases — gentle activation in week 1, then strengthening, then function — and each exercise belongs to a stage
- Regaining full extension (straightening) is the top priority — a knee that won't straighten makes every step painful and can stiffen permanently
- Quad sets and straight-leg raises wake up the thigh muscle that "switches off" after surgery and is key to walking again
- Heel slides are the main exercise for restoring how far your new knee will bend
- Manage swelling with ice and elevation, never prop a pillow under the knee, and avoid deep kneeling, squatting, or pivoting in the early weeks
Table of Contents
What Knee Replacement Recovery Involves
A total knee replacement (TKR) removes the worn, arthritic surfaces of the knee joint and caps them with metal and plastic components. It is one of the most successful operations in modern medicine — but the new joint only works as well as the rehabilitation behind it. Recovery is an active process, and the exercises you do at home are every bit as important as the surgery itself.
It helps to think of recovery in phases. In the first week or two, the focus is gentle: reducing swelling, getting the thigh muscle firing again, and beginning to move the joint. In the middle weeks (roughly 2 to 6), you progress to strengthening and to actively regaining your range of motion — both the bend and the straightening. From around six weeks onward, the emphasis shifts to function: standing, walking further, and rebuilding the everyday strength you had lost long before surgery.
Two numbers matter throughout. The first is extension — being able to straighten the knee completely flat. The second is flexion — how far the knee will bend, with around 90 degrees needed for stairs and 110-120 degrees the usual goal. Of the two, full extension is often the harder to win back, which is why so many early exercises are designed to straighten the knee.
Why Exercise Drives Your Recovery
After a knee replacement, exercise does several specific jobs that nothing else can:
- It reactivates the quadriceps. Surgery and swelling cause the big thigh muscle on the front to "switch off" — a phenomenon called quadriceps inhibition. Quad sets and straight-leg raises wake it back up, and without that muscle your knee feels unstable and walking is exhausting.
- It restores range of motion before scar tissue sets. Healing tissue inside the knee wants to tighten. Moving the joint daily — bending with heel slides, straightening with extension stretches — keeps it supple during the critical window when stiffness can become permanent.
- It controls swelling and prevents clots. Ankle pumps and gentle movement pump fluid and blood out of the leg, easing the swelling that limits your bend and reducing the risk of a dangerous blood clot.
- It rebuilds the strength to live independently. Functional exercises like sit-to-stand restore the power to rise from a chair, climb stairs, and walk — the abilities that knee arthritis had quietly stolen for years.
Because so much of recovery is leg strength, many of these movements overlap with general leg strengthening exercises for seniors. If your other knee or your hips are also stiff, the gentle, supported approach in our exercises for seniors with limited mobility pairs well with this routine.
10 Knee Replacement Exercises by Phase
Work within comfort, never into sharp pain, and always follow the specific guidance of your own surgeon and physiotherapist — the phases below are a general guide, not a substitute for their plan. Move slowly and breathe normally. A little discomfort and a stretching feeling are expected; sharp or increasing pain is your signal to ease off.
Phase 1: The First Week or Two — Activate & Settle
1. Ankle Pumps
Lie or sit with your operated leg supported and straight out in front of you. Slowly point your toes away from you, then pull them back up toward your shin, as if pressing and releasing a car pedal. Repeat 15-20 times, and aim to do this every waking hour in the first days. Ankle pumps are your very first exercise: they pump blood and fluid through the leg, bringing down swelling and sharply reducing the risk of a blood clot while you are less mobile.
2. Quad Sets
Sit or lie with your operated leg straight. Tighten the muscle on top of your thigh by pressing the back of your knee down toward the bed or floor, working to straighten the knee as fully as you can. You should see your kneecap pull upward slightly. Hold for 5 seconds, then relax. Repeat 10 times, several times a day. This deceptively simple exercise reawakens the quadriceps and is one of the most important moves for regaining full extension.
3. Gluteal Squeezes
Lie or sit comfortably with both legs supported. Squeeze your buttock muscles together firmly, as if holding a coin between them, hold for 5 seconds, then release. Repeat 10-15 times. While your operated leg does less in these early days, keeping the buttock and hip muscles strong matters — they help stabilise the leg and power you upright once you are standing and walking again.
4. Heel Slides (Knee Bends)
Lie on your back, or sit with your leg out straight on a smooth surface. Slowly slide your heel toward your buttock, letting the operated knee bend as far as is comfortable, then slide it back out until the leg is straight again. Repeat 10 times. Heel slides are the cornerstone exercise for regaining flexion — the bend in your knee. Go gently, respect the stretch, and expect a little more range each day.
Phase 2: Weeks 2 to 6 — Restore Motion & Strength
5. Heel-Prop Extension Stretch
Sit or lie with your heel propped up on a low stool or a rolled towel so your knee is unsupported and hangs in the air. Relax your thigh completely and let gravity slowly draw the knee down toward straight. Hold for 1-2 minutes — do not bounce or force it. Repeat 2-3 times a day. This patient stretch is how you recover those last stubborn degrees of full extension, which is essential for a smooth, pain-free walking stride.
6. Seated Knee Extensions
Sit tall in a sturdy chair with both feet flat on the floor. Slowly straighten your operated knee until your leg is extended out in front of you, hold for 3-5 seconds, then lower it back down under control. Repeat 10-12 times. This is a direct quadriceps builder that rebuilds the strength to straighten your knee against gravity — the exact action you use to walk and to stand from a chair.
7. Straight-Leg Raises
Lie on your back with your good knee bent, foot flat, and your operated leg straight out. First tighten your thigh to lock the knee fully straight, then lift the whole straight leg about 12 inches off the surface. Hold briefly, then lower slowly. Repeat 10 times. Because the knee stays straight throughout, this strengthens the quadriceps powerfully without bending or stressing the healing joint — only attempt it once you can do a strong quad set with no lag.
8. Seated Marching
Sit tall in a chair with your feet flat. Slowly lift your operated knee up toward your chest as far as is comfortable, then lower it back down, and alternate with the other leg as if marching in slow motion. Repeat 10 times per leg. This controlled movement gently improves your knee bend while rebuilding the hip-flexor and thigh strength you need to lift your leg when walking and climbing stairs.
Phase 3: From Six Weeks — Rebuild Function
9. Sit-to-Stand
Sit toward the front of a sturdy chair with your feet flat and drawn slightly back. Lean your chest forward over your knees, then stand up using both legs as evenly as you can, taking care not to let the operated leg do less work. Lower yourself slowly back down without dropping into the seat. Repeat 8-10 times, using the armrests for help at first and relying on them less as you get stronger. This rebuilds the practical leg strength you use dozens of times every day.
10. Supported Mini Knee Bends
Stand tall holding a kitchen counter or a sturdy chair with both hands for support. Keeping your back straight and your weight even, bend both knees a small way — no more than a quarter of the way down — then straighten back up. Repeat 10 times. These shallow, controlled bends build standing strength and confidence in your new knee. Keep them shallow on purpose: deep squatting is off-limits while you heal, so never bend past the point of comfort.
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Movements to Avoid After a Knee Replacement
Important: never prop a pillow under your knee
It is tempting to rest with a pillow tucked under the operated knee because the slight bend feels comfortable. Don't. Leaving the knee bent for long periods is the single most common reason people fail to regain full extension and end up with a permanently stiff, slightly bent knee. When resting, keep the leg out straight, and elevate it by propping under the heel — not the knee.
In the early weeks especially, avoid or carefully modify the following:
- Deep kneeling: Kneeling directly on the new joint is uncomfortable and best avoided until your surgeon clears it, which may be several months out, if at all.
- Squatting below 90 degrees: Deep squats place high load on the healing joint and surrounding tissue. Keep any bends shallow and supported in the early phases.
- Twisting or pivoting on the operated leg: Never plant the foot and swivel your body over it. To turn, take small steps and rotate your whole body, keeping your knee and foot pointing the same way.
- High-impact activity: Running, jumping, and jarring sports stress the implant and should be avoided permanently — choose walking, cycling, and swimming instead.
- Pushing through sharp pain: A gentle stretch is fine, but sharp or escalating pain, especially with a sudden increase in swelling, means stop and rest.
If long-standing arthritis in your other joints also flares as you become more active, the joint-friendly movements in our chair exercises for arthritis can keep you moving comfortably between rehab sessions.
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Little and often beats long, occasional sessions. Most physiotherapists recommend working through your prescribed exercises two or three times a day rather than all at once — short sets keep the joint moving without overloading it. Between sessions, manage swelling with the RICE approach: rest, ice the knee for 15-20 minutes, gentle compression, and elevate the leg above heart level. Mild swelling can persist for months and is normal; it is the sudden, sharp increases that warrant caution.
Pace your progress by your own week-on-week gains, not by comparison with anyone else — recovery timelines vary widely. As your operated knee grows stronger and steadier, you can begin folding in gentle whole-body movement and balance work to rebuild overall fitness; our chair exercises for seniors are an easy, low-pressure way to do that. Above all, keep your follow-up physiotherapy appointments, as a professional can measure your range of motion and adjust your exercises to exactly where you are.
When to See a Doctor
Some swelling, bruising, warmth, and discomfort are a normal part of healing. However, certain warning signs after a knee replacement need prompt medical attention. Contact your surgeon, physiotherapist, or doctor — or seek urgent care — if you notice:
- Calf pain, tenderness, or swelling, especially in one leg, which can signal a blood clot (deep vein thrombosis)
- Sudden shortness of breath or chest pain — treat this as an emergency, as it may indicate a clot has travelled to the lungs
- Fever, chills, or increasing redness, warmth, or fluid draining from the incision, which can mean infection
- A sudden, sharp increase in pain or swelling, or the knee giving way or feeling unstable
- Stalled progress — if your knee is not getting easier to bend or straighten over the weeks, tell your physiotherapist, as you may need extra help before stiffness sets in
Your surgeon and physiotherapist know the details of your operation and should always have the final say on your exercises and timeline. When in doubt, ask them before progressing.
Frequently Asked Questions
How soon after a knee replacement can I start exercising?
Gentle exercises such as ankle pumps, quad sets, and heel slides usually begin the same day or the day after surgery, while you are still in hospital. Your surgical team and physiotherapist will guide the timing. Early, gentle movement reduces swelling, prevents blood clots, and is one of the most important parts of a successful recovery.
Why is it so important to fully straighten the knee after a knee replacement?
Regaining full extension — the ability to straighten the knee completely — is critical because a knee that stays slightly bent makes walking painful and exhausting and can become permanently stiff if scar tissue sets. Exercises like quad sets, straight-leg raises, and heel-prop stretches all work to recover that last few degrees of straightening, which is often harder to regain than bending.
Which movements should I avoid after a knee replacement?
In the early weeks avoid deep kneeling, squatting below 90 degrees, and any twisting or pivoting on the operated leg, as these stress the healing joint. Do not place a pillow under the knee while resting, because it encourages the knee to stiffen in a bent position. Avoid high-impact activities such as running and jumping permanently to protect the implant.
How do I manage swelling so I can keep exercising?
Use the RICE approach between exercise sessions: rest, ice the knee for 15-20 minutes, gentle compression, and elevate the leg above heart level. Ankle pumps also help pump fluid away from the joint. Some swelling is normal for months, but it should ease with elevation and ice — exercise through mild swelling, but stop if it worsens sharply.
When will I be able to bend my new knee normally again?
Most people regain enough bend (around 90 degrees) to climb stairs and sit comfortably within 4 to 6 weeks, and continue improving toward 110-120 degrees over three months. Heel slides and seated knee bends are the key exercises for restoring flexion. Progress varies, so compare yourself to your own week-by-week gains rather than to anyone else.
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