The risk is 1-2%. May be doubled in diabetic patients and those that are obese. The risk of MRSA is much less than this. Antibiotics are given to prevent infection before and after surgery. Most infection respond to antibiotics.
Blood clots (deep vein thrombosis)
This risk is also 1-2%. This is prevented by keeping you well hydrated, giving you special stockings to wear and also medicine to thin your blood throughout your hospital stay. Getting out of bed as soon as possible after surgery also minimises this risk. Rarely the blood clot can dislodge from the leg veins and travel to the lung with serious consequences. (Pulmonary embolism).
Some force is required to attach the prosthesis to your bone. In doing so there is a risk of bone fracture. Any fracture occurring during surgery will be treated right away. This does not cause any long term problems but may prolong your requirement crutches post operatively.
Nerve and Artery Damage
Important nerves and arteries are in close proximity to the knee joint and hence are at risk of trauma during surgery. The risk to these structures is usually small.
Though most patients limp after surgery, this usually improves. The limp is due to weakness of the muscles around the knee as they have been cut during surgery. As they heal, the limp improves. In patients who were unable to exercise before surgery, the muscle becomes very weak. Following surgery a full recovery may not be possible.
Most prostheses should last 10- 15 years. Many last beyond that if you keep your weight under control and avoiding activities that put excessive strain on the knee.