Knee replacement, also known as total knee arthroplasty (TKA), is a surgical procedure designed to replace a damaged knee joint with artificial components, or prostheses. This intervention aims to alleviate severe pain and improve function, commonly for those with advanced osteoarthritis. Many believe that once a knee is replaced, future arthritis-related pain is eliminated.
The Primary Goal of Knee Replacement
Knee replacement surgery addresses severe osteoarthritis within the knee joint. During surgery, damaged cartilage and bone are removed from the ends of the thighbone (femur) and shinbone (tibia), and sometimes the kneecap (patella). These damaged surfaces are replaced with smooth, artificial parts made of metal and plastic. This eliminates osteoarthritis pain in that joint, allowing for smoother movement and reduced discomfort. The surgery does not treat other forms of arthritis, such as rheumatoid arthritis or psoriatic arthritis, nor does it address osteoarthritis present in other joints.
Arthritis in Other Body Areas
Having a knee replacement does not prevent arthritis from developing or persisting in other joints. For individuals with systemic arthritis, such as rheumatoid arthritis, psoriatic arthritis, or lupus, the disease affects the body. While knee replacement addresses structural damage in one knee, the underlying systemic condition can continue to cause inflammation and pain in other joints. These conditions can impact areas like the hips, hands, spine, or even the other knee, as they are part of a widespread immune response. Gout, another inflammatory arthritis, can also affect other joints, and the risk of developing gout may be higher after total knee arthroplasty.
Many people develop multifocal osteoarthritis in multiple joints due to age, genetics, or cumulative wear and tear. A knee replacement only targets the affected knee; it does not stop the progression of osteoarthritis in other areas. Therefore, osteoarthritis can develop or worsen in the other knee, hips, spine, or other weight-bearing joints, leading to new pain.
Persistent or New Arthritis in the Replaced Knee
While a knee replacement removes the source of osteoarthritis in the operated joint, other conditions can cause pain or inflammation similar to arthritis symptoms. If a patient has systemic inflammatory arthritis, such as rheumatoid arthritis or gout, that was not controlled, it can affect tissues surrounding the prosthetic joint. This can lead to inflammation and pain in the replaced knee, even though the original osteoarthritis is gone.
Complications related to the surgery or implant can also cause symptoms resembling arthritis. An infection around the prosthetic joint (periprosthetic joint infection) can cause persistent pain, swelling, redness, warmth, and fever or chills. Loosening of prosthetic components from the bone, or a periprosthetic fracture (a broken bone around the implant), can also result in pain, instability, and reduced function. These issues are mechanical or biological problems related to the artificial joint or surgical site, distinct from a recurrence of the original osteoarthritis. If the kneecap (patella) component was not fully replaced or the original osteoarthritis was more extensive, patellofemoral arthritis can still cause pain in the front of the knee.
Identifying and Addressing Post-Replacement Arthritis
Recognizing symptoms that indicate new or persistent arthritis, or arthritis-like complications, after knee replacement is important. Common signs include persistent pain beyond typical recovery, swelling, stiffness, warmth, or redness around the replaced knee or in other joints. Instability or unusual drainage from the surgical site can also be concerning. These symptoms differ from the normal, expected pain and discomfort associated with initial healing, which subsides over several weeks to months.
If these symptoms are worsening, severe, or do not improve, consult an orthopedic surgeon or primary care physician. A doctor will perform a physical examination and may order diagnostic tests to determine the cause of the pain. These tests can include blood tests for inflammatory markers (C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR)), or imaging studies like X-rays, MRI, or CT scans to assess the implant and surrounding bone.
Management strategies depend on the specific diagnosis. For arthritis in other joints, treatment may involve medication (non-steroidal anti-inflammatory drugs (NSAIDs) or disease-modifying antirheumatic drugs (DMARDS)), physical therapy, and lifestyle modifications. If inflammatory arthritis affects the replaced knee, specific medications may be used to control the underlying condition. Mechanical issues with the implant, like loosening or fracture, may necessitate further surgical intervention, such as revision surgery. Infections require antibiotics and potentially surgical debridement or implant removal.