Persistent Knee Pain After Knee Replacement

Persistent Pain After Knee Arthroplasty or Prosthesis

Persistent pain after knee arthroplasty or prosthesis can have various causes, some of which are difficult to diagnose. However, it is possible to experience persistent pain even without obvious complications of the knee prosthesis.

Today, we can reasonably assert that modern knee prostheses should function for 10 to 20 years in 90% of patients. However, up to a quarter of patients undergoing knee replacement surgery report dissatisfaction with the procedure, experiencing knee pain due to the prosthesis.

Why Does Pain Persist After Knee Replacement Surgery?

Knee Prosthesis Infection

Infection can occur in the deep wound or around the prosthesis. This can happen during hospitalization or afterward, when you return home. It can also occur years after the surgery. Infections localized to the wound area are usually treated with antibiotics. Serious or deep infections may require further surgery, up to and including removal of the prosthesis. Any infection in your body, even far from your knee, can spread and affect your prosthesis.

Loosening of the Knee Prosthesis

In a complication called aseptic loosening, the prosthetic components gradually detach from the bone. The bonds holding the prosthesis to the bone are destroyed by the body's attempts to digest these particles. Furthermore, in this particle digestion process, the body also "digests" the bone. This phenomenon is called osteolysis. This can weaken or even fracture the bone and compromise the success of future revision surgery. Indeed, in this case, the surgical procedure will also have to deal with the problem derived from bone loss. There is a true rejection process of the knee prosthesis, accompanied by symptoms of varying severity.

When the prosthesis detaches from the bone, the patient may experience pain or instability, the intensity of which depends on how quickly the complication develops. Noises may be heard at the level of the knee prosthesis, there may be swelling of the knee with the prosthesis, or a clinical picture of tendinitis. Mobilization of the components usually requires surgical revision of the prosthesis.

Blood Clots (Thrombus)

Blood clots in the leg veins are the most frequent complication of knee arthroplasty. These clots can be life-threatening if they break loose and start moving towards the lungs, resulting in a pulmonary embolism. Your orthopedic surgeon will offer a prevention program, which may include periodically elevating your legs, early exercises to increase circulation, elastic stockings, and medication to facilitate blood flow (heparin).

Joint Stiffness with a Knee Prosthesis

In some cases, the knee with a prosthesis is not able to move in a way that allows normal daily activities. The prosthesis is then said to be stiff. This can be due to the formation of rigid scar tissue around the prosthesis, due to poorly performed rehabilitation, but also for reasons more properly related to the prosthesis itself. The choice of treatment to be performed depends above all on the time elapsed since the operation and the severity of the stiffness.

Non-Orthopedic Causes of Pain After Knee Replacement

Persistent knee pain with a prosthesis is not always due to implant complications. Pain can also have non-orthopedic causes, such as vascular problems, osteoarthritis of the hip or spine, neurological problems, or complex regional pain syndrome. Finally, complaints can be caused by psychological factors such as anxiety, depression, or unmet patient expectations. Patients who present at outpatient examinations with persistent pain after a knee prosthesis also need an individual clinical, psychological, and radiological diagnosis.

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Which Patients Have an Increased Risk of Prosthesis Failure?

Younger, more active patients are more likely to undergo revision surgery for complications related to a knee prosthesis. Obese patients have a higher incidence of wear and loosening of the prosthetic implant. Patients whose primary surgery was performed due to rheumatoid arthritis or avascular necrosis have a higher risk of loosening. Smoking or another immunocompromised state of the patient increases the risk of surgical site infection.

Are There Specific Tests for Painful Knee Prostheses?

In cases of prosthesis failure, there is an increase in pain, the appearance of noises in the knee prosthesis, or a decrease in knee articulation. Mechanical failure or infection of the prosthesis can also manifest as redness and warmth, or swelling of the knee after prosthetic surgery. A limp or obvious deformity may be present. In some cases, especially in people allergic to prosthesis components, X-rays, blood tests, and even scintigraphy may be normal. Symptoms, especially in case of rejection (or loosening) or infection of a knee prosthesis, can be very varied. Hence the need for a codified diagnostic strategy. In these cases, you should contact your referring surgeon who, in addition to an anamnestic and clinical examination, will request the first diagnostic tests (generally X-rays and some laboratory tests). Then, always depending on the clinical picture, aspiration of the intra-articular fluid, a CT scan, or scintigraphy may be performed.

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