Total knee replacement (TKR) surgery relieves chronic pain and restores mobility. While most artificial joints function well for many years, a total knee replacement can fail over time due to various complications. Recognizing the warning signs of a failing implant is important for timely diagnosis and intervention.
Persistent Pain and Swelling
Pain that persists or returns long after the initial surgical recovery period often signals a problem with the knee replacement itself. The first three to six months typically involve some discomfort, but pain that returns months or even years later, particularly with activity, is a common symptom of implant failure. This type of chronic pain is frequently associated with aseptic loosening, where the bond between the implant and the bone weakens without the presence of infection.
Pain related to mechanical failure, such as component wear, often presents as a deep, throbbing ache that intensifies with weight-bearing activities. This discomfort may also become noticeable at rest or worsen significantly at night, potentially disrupting sleep. Wear particles from the plastic spacer can trigger an immune response, leading to bone loss (osteolysis), which compromises the implant’s fixation.
Chronic, unexplained swelling that does not resolve with typical measures like rest and elevation can also be a sign of underlying irritation or inflammation. The presence of warmth around the joint, without systemic fever, suggests an ongoing inflammatory process within the knee capsule. This localized swelling and warmth is often a reaction to the debris created by the friction of the implant components. The joint may feel full or “boggy” to the touch due to an excessive buildup of joint fluid, known as effusion.
Mechanical Issues and Joint Instability
Functional problems that limit daily activities are significant indicators that the mechanical integrity of the implant system is compromised. A feeling that the knee is unstable, sometimes described as the joint “giving way” or buckling during walking, is a primary sign of soft tissue imbalance or implant loosening. This instability can result from laxity in the surrounding ligaments or from subtle shifts in the implant components themselves.
Another common mechanical issue is a progressive loss of range of motion or an increase in joint stiffness. While some stiffness is common after surgery, a loss of the ability to bend or straighten the knee that was previously achieved is concerning. This functional limitation can make simple tasks, such as climbing stairs, getting out of a chair, or operating a vehicle, increasingly difficult.
Patients may also notice new, audible, or palpable sounds emanating from the knee during movement. Noises such as clicking, clunking, or grinding suggest that the metal or plastic surfaces of the implant are not articulating smoothly. These sounds can be caused by excessive wear of the plastic liner, misalignment of the components, or the presence of debris within the joint space.
Signs Suggesting Acute Infection
Periprosthetic joint infection (PJI) is a distinct and serious complication requiring immediate attention, as it can rapidly compromise the implant and surrounding tissue. Systemic symptoms often accompany an acute infection, including fever, chills, and generalized fatigue. These signs indicate that the body’s immune system is actively fighting bacteria that have colonized the artificial joint.
Localized signs of infection are usually present around the surgical incision site. Excessive redness, warmth, and increased tenderness are strong localized indicators of a problem. Of particular concern is any persistent drainage from the surgical wound or the development of a fistula, which is an abnormal tract connecting the joint space to the skin surface.
Persistent drainage from the wound is a definitive sign of infection. An acute infection can occur shortly after surgery or, in some cases, years later, often due to bacteria traveling from a separate infection site elsewhere in the body. Recognizing these specific signs and acting quickly is paramount to preventing significant bone and soft tissue destruction.
Consulting Your Healthcare Provider
If any suspicious symptoms arise, promptly contact the orthopedic surgeon or healthcare provider. Delaying evaluation can complicate the eventual treatment and potentially lead to more extensive damage to the joint.
The initial diagnostic process typically involves a combination of tests to pinpoint the cause of the problem. Standard X-rays evaluate component position and look for signs of loosening, such as a gap between the bone and the implant. Blood tests, specifically checking inflammatory markers like C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), help determine if an infection is present.
In cases where infection is suspected, a joint aspiration may be performed to draw fluid from the knee for laboratory analysis. This procedure allows for the definitive identification of bacteria and guides the choice of appropriate treatment. Other advanced imaging, such as a CT scan or MRI, may be ordered to assess soft tissues and better visualize the bone-implant interface.