Unicompartment Knee Replacement (Uni Knee)

What is unicompartmental knee arthritis?

Unicompartmental osteoarthritis of the knee is a condition in which degenerative arthritis affects only one part of the knee joint, while the other regions (or “compartments”) of the knee remain healthy or not significantly damaged.

Knee joint anatomy

The knee joint is composed of three bones: The femur (thighbone), the patella (kneecap) and the tibia (shinbone). Two knob-like protuberances on the bottom of the femur known as the femoral condyles make up the top of the knee. The upper portion of the tibia known, as the tibial plateau, makes up the bottom. The kneecap rests in front of the femoral condyles.

Illustration and X-ray images of medial compartment osteoarthritis of the knee

There are three compartments of the knee, each named for its relationship to these portions of bone:

  • The medial (inner) compartment of the knee.
  • The lateral (outer) compartment of the knee
  • Kneecap joint also called patellofemoral joint where patella tracks in front of the femur bone

Arthritis of the knee may occur in any one of these compartments. However, the medial compartment is the most frequent site of knee osteoarthritis, followed by the lateral compartment. (Arthritis that is confined to the patellofemoral joint (kneecap joint) of the knee is uncommon and will require an AVON patellofemoral joint replacement.)

What is partial knee replacement surgery?

Partial knee replacement is where the bone surfaces of only one compartment of the knee joint are removed and replaced with implants, as compared to that of multiple compartments in the case of a total knee replacement. It is a common treatment for unicompartmental arthritis.. In fact, recent data suggests that anywhere from 10% to 25% of all patients with osteoarthritis of the knee needing replacement surgery may be eligible for the procedure.

It is important to note that partial knee replacement has been known by several names including partial knee resurfacing procedure, half knee replacement,”unicompartmental knee replacement,” “unicondylar knee arthroplasty” or “unicondylar knee replacement.”

If I have partial knee replacement, does that mean that I will no longer have arthritis of the knee?

Partial knee replacement will address the arthritis that is present in the compartment of the knee that is already affected. While rare, there is no guarantee that arthritis will not progress elsewhere in the knee. Should this occur, a surgical revision to a total knee replacement may be necessary.

Who can benefit from partial knee replacement?

Partial knee replacement is appropriate for patients with arthritis that is confined to a single compartment of the knee and is restricted to patients who are not morbidly obese (BMI- Body Mass Index greater than 40). There should not be any stiffness or angular deformity of the knee as partial knee replacement is not a deformity correcting surgery and is strictly a resurfacing procedure where the damaged surfaces are replaced. Further, candidates who suffer from inflammatory arthritis including rheumatoid arthritis or psoriatic arthritis benefit from total knee replacement rather than partial knee replacement. Selecting the right patient is considered one of the most important steps to ensuring a good functional outcome and longevity for a partial knee replacement.

Are there any age restrictions for getting partial knee replacement surgery?

There are no strict recommendations, but in general, partial knee replacements are appropriate for patients over 40 -50 years old who meet other eligibility criteria.

What happens during partial knee replacement?

During partial knee replacement, the surgeon makes a small incision to gain access to the affected compartment of the knee. He or she gently moves supporting structures of the knee out of the way and removes damaged cartilage and bone tissue from the surfaces of the tibia and the femur in the arthritic area. The prepared surfaces are then templated for the prosthetic knee implants when are then cemented into place.

What kind of anaesthesia is used during partial knee replacement surgery?

Regional anaesthesia, also called spinal anaesthesia, which numbs the lower half of the body and allows the patient to remain awake during the procedure. Nerve blocks are often added for postoperative pain relief in addition to the surgeon injecting a cocktail of drugs around the knee during surgery This cocktail may contain a local anaesthetic plus one or more pain medications, corticosteroids or other agents. Throughout partial knee replacement surgery, patients are carefully monitored to minimize the risk of complications.

Is partial knee replacement painful?

Knee replacement, either partial or total, will always result in some amount of pain after the surgery.. Immediate postoperative pain relief is provided by prolonged anaesthetic effects of spinal anaesthesia along with the effects from the cocktail mixture injected around the knee during surgery. Patients will also receive pain medications as standard in the first few days after surgery.

What is a partial knee replacement prosthesis made of?

All knee replacement prostheses or implants are made of metal and plastic. These surfaces are designed to glide smoothly against one another, just as cartilage does in a healthy knee. Depending on which compartment is affected and whether the patient’s anterior cruciate ligament (ACL) is intact, the surgeon will use either a unicondylar fixed-bearing knee replacement − the most used prosthesis − or a mobile-bearing unicondylar knee replacement.

What is the recovery time for partial knee replacement?

Most patients can expect to be back to their daily activities within three to six weeks. Many patients find that after undergoing physical rehabilitation, they can return to sports such as golf within 6 to 10 weeks. Patients can usually expect to go home the same day of surgery, unless they have a medical condition that requires an overnight stay. Most patients are also able to walk with assistance, or independently, on the same day as their surgery. Typically, the patient is given a cane within days of surgery to allow for increased independence and begins outpatient rehabilitation. Patients are often finished taking prescription pain medication within one to two weeks after surgery.

Will I be able to return to playing sports after my partial knee replacement?

By 3 months, most patients will be able to resume sporting activities including playing golf and badminton. It is generally not advisable to play impact sports like football or rugby.

What are the possible complications of partial knee?

As with any joint replacement surgery, complications may include instability of the knee, loosening of the implant, infection, nerve injury and deep vein thrombosis.. Be sure to discuss any concerns you have regarding these or other issues with your surgeon.
Patients who have been properly screened for the procedure can expect to experience a low level of complications and a rapid recovery. However, as with other types of knee surgery, in a small percentage of cases, revision surgeries are required. Results obtained with revision surgery may not be as good as those achieved with primary surgery.

How long does a partial knee replacement last?

A well-done partial knee replacement in an appropriately selected patient can have an implant survival rate that is comparable to that achieved with a total knee replacement in the first decade following surgery. (90% survival rate at 10 years)

Front View Of Uni Knee

Side View Of Uni