The term startup stiffness describes the feeling of the knee needing a few steps to ‘loosen up’ when you stand from sitting. Sitting for as little as half an hour can create this sensation and usually 5 or 6 steps are enough for the knee to start moving properly again.
One of the theories as to why this happens is that, with rest, the joint fluid is not moved around to coat the joint. Normally when the joint is used the joint fluid bathes the joint and keeps it well lubricated. The more the joint is used, the more the joint fluid coats and lubricates the inner joint. In an arthritic joint, there is less cartilage and less joint fluid The joint fluid that is there is more watery and not as good at lubricating the joint and the cartilage that is there is of poorer quality.
As a result, in an arthritic joint, the process of lubricating the joint with the joint fluid that is being stored in the cartilage is less efficient and less effective. Unfortunately once an arthritic joint has “warmed up” it starts to feel better, if it is used for a long time, it often starts to become more and more painful until it is rested. Stretching and strengthening the muscles surrounding arthritic joints helps take the pressure off the joint so that they are less painful and less stiff when they first start moving, and also less painful and stiff while they are being used.
The pain is often worse at the end of the day or after a long time spent standing or walking on the bad leg. The most common cause of startup stiffness is osteoarthritis of the knee. It is usually associated with joint swelling, loss of motion and pain. Initially it will respond to physiotherapy, weight loss, anti-inflammatory tablets and cortisone injections but eventually the only option is to perform a total knee replacement.