Knee Replacement Exercises: Pre-op and Post-op Physiotherapy

Knee replacement exercises start the day of or the day after surgery and continue for months, and bending the knee is the single most important early goal. Physiotherapy and daily exercises are the heart of recovery, because regaining range of movement early is far easier than recovering it later¹. Doing them little and often, fully straightening as well as bending the knee, is what separates a smooth recovery from a stiff one.

I will be honest: the bending exercises were the hardest and most uncomfortable part of my recovery, and also the part that mattered most. Nobody quite prepared me for how much they ask of you when the knee is swollen and sore. This guide, checked by a consultant orthopaedic surgeon, covers what to do before surgery and after, and pairs with the knee replacement recovery timeline and our main guide to knee replacement surgery.

Why exercises matter so much

Exercises matter because they restore movement, rebuild the muscles that surgery weakens, and prevent the stiffness that is the most common problem after a knee replacement. Physiotherapy and daily exercises begin the day of or the day after surgery and continue for months, with bending the knee as the key early goal².

There is a clear reason for the urgency. Scar tissue forms in the weeks after surgery, and a knee that is moved early and often stays supple, whereas a knee left to settle stiffens up. If the knee will not bend far enough despite consistent exercise, a manipulation under anaesthetic (MUA) is a recognised early treatment, which we explain in regaining knee bend and avoiding stiffness. The best way to avoid one is to do the work early.

Exercises before surgery (prehab)

Before surgery, prehab exercises strengthen the muscles around the knee and improve your general fitness, which speeds your recovery afterwards. Stronger quadriceps and better fitness going in tend to mean an easier early recovery³. Useful pre-op exercises, within the limits of your arthritis pain, include:

• Static quadriceps contractions: tighten the thigh to press the back of the knee down, hold, and release.
• Straight-leg raises: lift the straight leg a short way off the bed and lower it slowly.
• Seated knee bends: slide the foot back to bend the knee as far as is comfortable.
• Walking and gentle cardio: to keep your heart and lungs in good shape for surgery.

I did very little prehab before mine, and with hindsight I wish I had done more, because the stronger leg recovers faster. If pain limits you, ask your physiotherapist which exercises are safe.

The key post-op exercises

After surgery, the core exercises restore the knee’s ability to bend and fully straighten, and rebuild strength. The American Academy of Orthopaedic Surgeons publishes a standard exercise programme that physiotherapists draw on¹. The early staples are:

• Ankle pumps: move the foot up and down to keep blood flowing and lower clot risk.
• Heel slides: slide the heel towards you to bend the knee, the cornerstone bending exercise.
• Seated knee bends: let the foot drop back under the chair to deepen the bend.
• Quadriceps sets and straight-leg raises: rebuild the thigh muscle that controls the knee.
• Knee straightening (extension): sit with the heel propped to let the knee fully straighten, which is as important as bending.

Fully straightening the knee is easy to neglect and just as important as bending it; a knee that does not straighten makes walking harder for good.

How often and how hard to exercise

Do the exercises little and often: several short sessions a day rather than one long, punishing one. Most programmes suggest exercises a few times daily in the early weeks². Consistency beats intensity, and a swollen knee tolerates frequent short bursts far better than one marathon session.

Practical tips from my own recovery: take your pain relief about half an hour before a session so you can move further, and ice the knee afterwards to settle the swelling. The exercises are uncomfortable, and that is expected, but sharp or new pain is not, and should be reported to your physiotherapist. Pair your exercise routine with good pain management after knee replacement so the discomfort never stops you doing the work.

When to progress and when to ask for help

Progress your exercises only as your physiotherapist directs, and ask for help if your range of movement stalls. Your physiotherapist sets personal bending targets and progresses them at each visit, adding resistance, cycling, or balance work as you improve³.

Speak up early if the knee is not bending further week on week, because a stalling range of movement is exactly the situation where a manipulation under anaesthetic is considered. Honestly, the people I have spoken to who struggled most were the ones who quietly let the exercises slide; the ones who kept at the uncomfortable bending did best. For the wider recovery picture, follow the week-by-week recovery timeline.