A partial knee replacement is an alternative to total knee replacement for some patients with osteoarthritis of the knee when the damage is confined to a particular compartment of the knee. In the past, partial knee replacement was reserved for older patients who were involved in few activities. Now, with better implants and improved surgical techniques, more patients are being considered for partial knee replacement compared with a few years ago. About 5% to 6% of patients with arthritic knees are estimated to be eligible for partial knee replacement.
How common is knee osteoarthritis?
Up to 30% of the population is believed to have knee osteoarthritis. Until age 50, knee osteoarthritis is equally common in men and women. After age 50, more women are affected.
What is osteoarthritis?
Osteoarthritis is the wearing away of the connective tissue called articular cartilage within the joint. Articular cartilage prevents one bone from scraping against another. The cartilage acts as a shock absorber in the joint and allows for smooth and stable movement within the joint. When the cartilage thins, the joint can inflame and you may feel pain and stiffness in the joint and your range of motion may be limited.
What is a partial knee replacement?
In a partial knee replacement, only the damaged part of the knee cartilage is replaced with a prosthesis.
What are the advantages of partial knee replacement over total knee replacement?
Compared to total knee replacement, partial knee replacement better preserves range of motion and knee function because it preserves healthy tissue and bone in the knee. For these reasons, patients tend to be more satisfied with partial knee replacement compared with total knee replacement, and they are still candidates for total knee replacement should they ever need it in the future. There is also less blood loss during surgery, and knee motion recovers faster with partial knee replacement.
Who is a candidate for partial knee replacement?
Patients with medial, lateral, or patellofemoral knee osteoarthritis can be considered for partial knee replacement. "Medial" refers to the inside compartment of the joint, which is the compartment nearest the opposite knee, while "lateral" refers to the outside compartment farthest from the opposite knee. Medial knee osteoarthritis is commonly caused by damage to knee cartilages, known as the menisci.
Patellofemoral osteoarthritis is osteoarthritis of the joint between the kneecap (patella) and the lower leg bone (tibia). This type of knee osteoarthritis is more common than lateral compartment knee osteoarthritis.
If your knee pain persists despite anti-inflammatory medications and maintaining a healthy weight, you may want to consider a knee replacement.
Your doctor will ask you to identify the area of pain in your knee, then check your range of motion and the knee's stability. An X-ray of the knee will determine your eligibility for partial knee replacement but your surgeon may not know for certain if you are a good candidate until the surgery has begun. To be a candidate, you must have an intact anterior cruciate ligament, a sufficient range of knee motion, limited inflammation, minimal pain at rest, damage to only one compartment, and no calcification of cartilage or knee dislocation.
In the past, a partial knee replacement was considered only in patients older than 60 years who were sedentary but younger, more active patients are increasingly being considered.
What is recovery like?
You can start moving the knee the day after surgery. Your knee function should return rapidly and with less pain than with total knee replacement. You will work with a physical therapist to mobilize the knee while in the hospital and for 2 to 4 weeks after discharge, which usually occurs no later than 1 or 2 days after surgery.
You will need medication to guard against formation of a blood clot while in the hospital and perhaps for a period of time after you are discharged.
If all goes well, you should be back to full activity in about 1 month. Impact exercises or jogging/running may not be recommended because the replacement includes a bearing surface that can wear.
What are the risks?
An infection at the surgical site is possible. Blood clots are a risk as are injuries to a blood vessel or a nerve. These complications are quite rare. You may experience some knee joint stiffness.
Late complications may include infection and a failure, loosening, or dislocation of the prosthesis as well as continued pain.
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