Knee replacement physiotherapy is a delicate job, because the joint itself is highly sophisticated. What may seem at first glance 'just a forwards-and-backwards hinge' bending and straightening the leg so you can walk and sit comfortably, is really much more complicated than that. The knee joint has a delicate swivel mechanism that locks the knee home - so you can brace the leg back straight and it will stay there with minimal muscle effort. In other words, the leg won't buckle under as you take weight on it.
Good alignment is the most important requirement for success
By contrast, total hip joint (yes, I know this article is about knees) has none of these invisible inner tricks. The hip is a dumb old joint; a load-bearing workhorse for the body, at the junction where the legs join the torso. In engineering terms it’s a universal joint with a wide range of movement in many directions. And because it’s such a relatively uncomplicated joint, it’s easy for man to replicate. In fact, the surgical procedure called ‘total hip replacement’ is the most successful orthopaedic procedure.
But back to knees. With re-education after knee surgery, knee replacement physiotherapy must mentally prepare patients that the locking must be worked at actively in the rehabilitation period. Usually, in the lead-up to surgery (most commonly for osteoarthritic knees) the quadriceps muscles on the inner side of the thigh (vastus medialis) has become weak, simply because it is often too painful to brace the leg back straight.
Indeed, in the journey of degeneration, when knees get to the point of not straightening completely, their deterioration accelerates because bent knees are much more wobbly, read unstable, in the lateral direction. For these reasons knee replacement physiotherapy must concentrate on strengthening the muscles that control the knee joint in its last few degrees of straightening - so the artificial device is not challenged.
If the leg remains at all bent after surgery - either inwards with a knock-kneed alignment, or outwards as in bow-legged - the device will break down much more rapidly and require what is termed euphemistically ‘revision’.
Knee replacement physiotherapy must do its best to make good what it inherits after surgery and this may include using small wedges under the inside of the heel, for knock, or the outside for bowed legs. The purpose of this is to minutely alter the angle of the forces passing through the joint. I ask patients to wear these inside the shoe to give the knee replacement a longer life. Incidentally, I also use heel wedges pre-operatively to make the knees more comfortable and delay surgery.
Oh! And the final point to make in the journey of post-operative knee rehabilitation is about the walking.
That is, not walking like daffy duck with the toes pointing out, nor pidgeon toed. Ideal forward and back foot alignment does not introduce extraneous movement to the artificial hinge and this too gives it a longer life. Even a few degrees makes a difference.
And finally, finally if you want to avoid surgery in the first place, have a look at 'Knees' in my Body in Action.
While you are thinking about that, you can click below here to listen to a most interesting radio program broadcast several years ago in Australia about knees, especially if you’re thinking about knee surgery It is essential listening, broadcast as a two part program called 'The Knee Files'. Apart from other things it goes into the work of Professor Graeme Jones, Head of the Musculo Skeletal Unit of the Menzies Institute and his refreshingly good news that knee cartilage does indeed regenerate.
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