The signs and symptoms of joint replacement failure can take range from the subtle to the obvious.  Sometimes, the symptoms may be evident soon after a failed surgery, but not all pain after surgery means that revision surgery is necessary.

Pain
When prosthetic components begin to fail, issues such as fracture of the plastic spacer located between the metallic implants can occur from abnormal wear patterns or improper surgical techniques.  While rare, 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 severe if the fracture of the plastic occurs suddenly.

Thigh or groin pain is the primary symptom of stem loosening in hip replacement, especially during walking. Sometimes, the pain can radiate to the knee.  Knee pain, often at the start of activities, can also be a sign of implant loosening.

Instability
Instability in the knee often feels like the knee wants to give out with standing or walking. This is frequently caused by excessive wear of the plastic spacer, causing it to be thinner than it was at the time of surgery. Ligaments become loosened, making your knee or hip joint less stable.  Hip instability can present as joint subluxation or dislocation.

Warmth
In addition to the swelling that can occur, another symptom of a failing prosthesis can include noticeable warmth of the joint. 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 caused by inflammation.

Swelling
Swelling occurs as a result of inflammation of the lining of the joint, which in turn stimulates production of fluid. This is the body's response to irritation, causing swelling in the hip or knee. This irritation is frequently caused by the presence of microscopic pieces of plastic in the knee fluid, as well as the instability caused by loosening of the joint.

While pain can sometimes persist immediately after joint replacement, in most cases it is expected to resolve on its own.  Most often, pain that persists beyond one year can be evaluated for possible revision surgery.  The most important sign to have evaluation of a joint replacement is new onset pain, in a previously well functioning joint.  This change is often an indication that xrays and examination are needed.