What is Unicompartmental Knee Replacement?

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  • Written By: Marjorie McAtee
  • Edited By: W. Everett
  • Last Modified Date: 07 October 2019
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A unicompartmental knee replacement, or partial knee replacement, is a surgery used to replace damaged parts of the knee. It is different from a total knee replacement because it only replaces a part of the joint, rather than the entire joint. Surgeons use prosthetic implants to replace damaged medial or lateral parts of the injured knee joint. The procedure requires general anesthetic, and recovery may involve up to six months of physical therapy. Like any surgery, unicompartmental knee replacement carries risks, but most patients are able to walk without a cane soon after the procedure.

Patients who receive unicompartmental knee replacement surgery are typically placed under general anesthesia, so that they are unconscious during the surgery. The surgeon will generally need to make an incision about 3 inches long (7.6 cm) over the injured knee. This incision can allow the surgeon to evaluate the extent of the damage to the joint. The surgeon can then replace the damaged components of the joint with a metal or plastic prosthesis. Surgeons usually anchor the prosthesis in place with bone cement before closing up the incision.


The risks of unicompartmental knee replacement surgery can include bleeding and infection, just as with any other surgery. The risks of going under anesthesia can include breathing problems and allergic reactions to the drug. Risks specific to this procedure can include the accumulation of fluid in the knee joint, deep vein thrombosis, implant failure, damage to blood vessels and nerves, and pain in the knee while kneeling. Rarely, patients may develop complex regional pain syndrome, or CRPS. CRPS is a chronic pain disorder that causes a strong sensation of burning pain in the affected joint and limb.

Patients about to undergo unicompartmental knee replacement are usually advised to quit smoking and quit taking drugs that thin the blood, including aspirin. Patients are typically advised to discuss their medical history with their doctors before the surgery. A visit to the physical therapist before surgery can help patients prepare for recovery in advance.

Following the procedure, most patients are sent directly home. The repaired joint can usually support the patient's full weight right away. Most patients are able to walk without assistance one or two weeks after the procedure. Lengthy stays in physical therapy facilities are not generally considered necessary during recovery from unicompartmental knee surgery.



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