Last updated: 11/24/2009

In most cases, increasing pain, stiffness, and loss of mobility in the knee joint are early indications that the patient may benefit from revision surgery. The location of the pain may point to the part of the prosthesis that has been affected by osteolysis....

Pain around or in the kneecap is not always significant by itself because many TKR patients have occasional discomfort in that area after their knee replacement. If the pain is diffuse (felt throughout the knee rather than in only one part of the knee), it may indicate either an infection or loosening of the prosthesis. Pain felt throughout the knee accompanied by tissue fluid accumulating in the joint points to a problem with the polyethylene part of the prosthesis. Pain in the lower thigh or in the part of the leg just below the knee suggests that the metal plate attached to the femur or the metal implant in the tibia may have come loose.

The doctor may take risk factors into account in assessing the likelihood of a failed knee prosthesis. Six factors have been identified as increasing a patient's risk of needing revision surgery within two years of knee replacement surgery:

• age (Younger patients tend to be more active and to wear out knee prostheses more rapidly than older ones.)
• a long hospital stay for the original knee surgery
• concurrent diseases or disorders
• any type of arthritis
• surgical complications during the first knee operation
• having the first knee operation performed at an urban hospital

The doctor will then usually order a series of imaging tests to determine the location of the problem and the extent of bone loss. X-ray studies can be used to check for complete dislocation of the prosthesis as well as loosening. Computed tomography appears to be more effective in detecting the early stages of osteolysis than x-ray studies. If the doctor suspects that the knee prosthesis has become infected, he or she will aspirate the joint. Aspiration is a procedure in which fluid is withdrawn from a joint through a needle and sent to a laboratory for analysis. The fluid will be cultured in order to identify the specific organism causing the infection.