Physiotherapy after knee replacement: the first twelve weeks

A knee replacement is a good operation with a demanding recovery. The surgery fixes the joint surfaces; almost everything else — how far it bends, how well it straightens, how confident you are on stairs — comes from what happens in the twelve weeks afterwards.

Week 0 to 2: straighten it

The single most neglected target after a knee replacement is full extension. Getting the knee completely straight is less satisfying than bending it, it hurts, and it is easy to avoid by propping a pillow under the knee — which is exactly how people end up with a permanent bend they cannot lose. Nothing goes under the knee. Support goes under the heel.

Alongside that: ankle pumps for circulation, quadriceps activation, assisted bending, and getting up and moving little and often. Ice and elevation are not optional extras at this stage; controlling swelling is what makes the movement possible.

Week 2 to 6: earn the range

The working target is around 90 degrees of bend by week two to three, progressing from there. Ninety degrees is not arbitrary — it is roughly what you need to sit down on an ordinary chair and get up again, and to manage stairs one at a time.

This is the window that decides the outcome. A knee that is still stiff at six weeks is much harder to free than one that is stiff at three, because the scar tissue forming inside the joint matures. If range is not progressing in this period, that is the moment to say so, not something to hope resolves.

Walking practice moves from a frame to a stick. Strength work starts properly: straight leg raises, sit-to-stand, step work, static cycling if you have access to a bike.

Week 6 to 12: make it useful

By now the target is normal walking without support, comfortable stairs, and 110 to 120 degrees of bend. Enough to get in and out of a car without planning it, and to ride a bicycle.

The work shifts to strength and balance. The operated leg has usually lost considerable quadriceps and glute strength — often from long before the surgery, because the knee was painful for years first. Rebuilding that is what stops the limp, and the limp is what causes the back and hip complaints that show up six months later.

What to expect beyond twelve weeks

Continued gradual improvement for a year or more. Swelling at the end of active days for six to twelve months. Occasional clicking, which is normal. Kneeling is uncomfortable for many people permanently, and that is worth knowing in advance rather than discovering.

Things worth reporting straight away

Calf pain and swelling. A wound that is opening, weeping or increasingly red. Fever. Pain that is escalating rather than easing after the first fortnight. Range that is going backwards. These go to your surgeon, not to the next scheduled physiotherapy session.

Why the setting matters early

For the first few weeks, getting to a clinic is often the hardest part of the day. Home treatment in that window is not a lesser option — it lets the therapist work with your actual stairs, your bed height and your bathroom, and it removes a car journey that costs you more than the session gains. Moving to a clinic later, once you can travel comfortably, gives you access to equipment that is difficult to replicate at home.