Knee replacement surgery can be a life-enhancing procedure for those who suffer from chronic, disabling end-stage arthritis. Quality of life can be improved immensely, and return to near-normal function and to activities of daily living are major goals of this type of surgery.
For all the benefits, however, knee replacement surgery does not come without its own set of risks and potential hazards. Failure of the components of a knee replacement can be a serious risk and, other than cases of acute traumatic injury, failure can often occur gradually. There are several symptoms associated with prosthetic failure. One must understand the differences between risks and symptoms.
Infection, implant loosening, knee cap dislocation and failure are but a few of the known risks or hazards. When failure does occur, how it is displayed in both objective physical signs as well as subjective complaints helps to separate physical complications from subjective symptoms.
Complications are situations that occur after surgery that create problems for the patient, such as infections, bone breakage and blood clots in the legs. Symptoms, however, are the clinical manifestations of these complications: subjective complaints if you will; like pain, swelling, stiffness, warmth to the joint and a feeling of instability, according to Total Joints.
Pain
When prosthetic components begin to fail, issues such as fracture of the plastic spacer located between the metallic femoral, or thigh bone, and tibial, or shin bone, implants can occur from abnormal wear patterns or improper implantation techniques. Plastic fracture fragments can dislodge and become stuck between these surfaces, causing pain and mobility problems. Pain can begin as a mild soreness, or it can be acute and severe if the fracture of the plastic occurs suddenly.
Swelling
When knee replacement implants fail, several different things can occur, such as plastic breakage and loosening of the individual implants. Loosening usually occurs from the microscopic migration of tiny particles of plastic, called polyethylene, between the interfaces of either the metal and plastic or the metal and bone. As this microscopic migration progresses, the tiny particles begin to cause the host bone to dissolve at these interfaces. This is called osteolysis.
Swelling occurs as a result of inflammation of the lining of the knee, called the synovium, which in turn stimulates the accelerated production of knee fluid. This is the body's response to irritation, and when fluid production exceeds resorption, there is a net accumulation called effusion. Synovial irritation is frequently caused by the presence of microscopic fragments of plastic in the knee fluid. as well as by instability caused by loosening.
Instability
Instability in the knee frequently manifests itself in subjective complaints of feeling that the knee wants to give out with ambulation or weight-bearing. This is frequently caused by excessive wear of the plastic spacer, causing it to be thinner than it was at the time of implantation. Ligaments become loosened, the joint capsule becomes redundant and the knee demonstrates a level of hyper-mobility from the loss of tension in the supportive tissues. This state of hyper-mobility and instability can magnify the subjective symptoms, and a vicious circle can ensue.
Warmth
In addition to the swelling that can occur, another symptom of a failing prosthesis can include noticeable warmth of the joint. It is a known fact that replaced knees can exhibit warmth in the joint for months after surgery, but this effect steadily decreases over time. The warmth associated with prosthetic failure can often be significant and associated with a level of redness of the skin secondary to inflammation.
