Partial knee replacement surgery only replaces the damaged cartilage in an arthritic knee instead of all of the knee cartilage. It has a number of benefits over total knee replacement surgery, including a smaller incision and quicker recovery. However, not all arthritis patients are qualified candidates for surgery, and unfortunately, most patients who would be qualified wait too long to consider surgery and then total knee replacement becomes the only option.
In partial knee replacement surgery, or unicompartmental knee arthroplasty, orthopedic surgeons replace either the inner or outer part of the damaged knee joint with a metal implant, and leave the rest of the healthy knee intact. So unlike full knee replacements, which removes all of the knee's cartilage whether it is damaged or not, the partial knee surgery only removes the damaged cartilage. The surgery may be considered for patients with osteoarthritis of the knee, whereas these patients would traditionally undergo full knee replacements.
Typical partial knee replacement surgery lasts about 1 1/2 hours. The surgeon will make an incision over the knee to expose the damaged cartilage. She will then cut flat and clean the rough edges of the femur (the long bone from the hip to the knee) and the tibia (the lower bone that runs from the knee to the ankle). Then the unicompartmental device is fitted and cemented into its place.
Candidates for Surgery
Patients are considered for partial knee replacement if they have severe arthritis of the knee and conservative treatments have failed. Some of these conservative treatments may include prescription medications, cortisone injections, physical therapy and weight loss. Partial knee surgery may only be possible if the arthritis is limited to a small area of the knee. If the arthritis is widespread beyond just the inner or just the outer regions of the knee, then partial knee replacement surgery is not an option. The best patients for this surgery are older than 55, not obese, and have their knee ligaments intact, especially the ACL. It's too risky to perform the partial surgery on a poor candidate, since the failure rates are high for these patients, and it may not be possible to convert a partial procedure to a total knee replacement. Unfortunately, most patients who require surgery have arthritis that is too advanced for the partial knee replacement procedure, as either they or their orthopedic surgeons wait too long before considering surgery.
Patients usually remain in the hospital for at least one night after surgery, and they are encouraged to put weight on their knees as soon as possible. Upon discharge, patients will have to start physical therapy and rehabilitation immediately, which will be customized for each patient. Surgeons will also require several follow-up appointments to track the recovery progress and to give better estimates as to when to expect a full recovery. The length of time differs for every patient, as it mostly depends on regaining muscle strength.
Partial knee replacement surgery has significant benefits over total knee replacements. For instance, the incision is much smaller. Full knee replacements require an 8-inch incision over the front of the knee, because surgeons have to dissect a considerable amount from the joint. Partial knee replacements only need a 3-inch incision due to the minimal amount of dissection and cartilage removal. Also due to the smaller amount of material removed, the partial knee replacement has far less loss of blood than a total knee replacement. Patients also have a shorter recovery time, both in and out of the hospital. Most patients with a partial knee replacement surgery are discharged from the hospital within 24 hours of the procedure, while patients with total knee replacement surgery rarely leave sooner than three days post-procedure. These patients also usually need to stay in a rehabilitation unit during their recovery.