A partial knee replacement is surgery to replace only one part of a damaged knee. It can replace either the inside (medial) part, the outside (lateral) part, or the kneecap part of the knee.
Surgery to replace the whole knee joint is called total knee replacement.
Partial knee replacement surgery removes damaged tissue and bone in the knee joint. The areas are replaced with a man-made implant, called a prosthetic.
Before surgery, you will be given medicine that blocks pain (anesthesia). You will have one of two anesthesia types:
- General anesthesia. You will be asleep and pain-free during the procedure.
- Regional (spinal or epidural) anesthesia. You will be numb below your waist. You will also get medicines to make you relax or feel sleepy.
The surgeon will make a cut over your knee. This cut is about 3 to 5 inches long.
- Next, the doctor looks at the entire knee joint. If there is damage to more than one part of your knee, you may need a total knee replacement. Most of the time this is not needed, because tests done before the procedure would have shown this damage.
- The damaged bone and tissue are removed.
- A part made from plastic and metal is placed into the knee.
- Once the part is in the proper place, it is attached with bone cement.
- The wound is closed with stitches.
Why the Procedure is Performed
The most common reason to have a knee joint replaced is to ease severe arthritis pain.
Your doctor may suggest knee joint replacement if:
- You can't sleep through the night because of knee pain.
- Your knee pain prevents you from doing daily activities.
- Your knee pain has not gotten better with other treatments.
You will need to understand what surgery and recovery will be like.
Partial knee arthroplasty may be a good choice if you have arthritis in only one side or part of the knee and:
- You are older, thin, and not very active.
- You do not have very bad arthritis on the other side of the knee or under the kneecap.
- You have only minor deformity in the knee.
- You have good range of motion in your knee.
- The ligaments in your knee are stable.
However, most people with knee arthritis have a surgery called a total knee arthroplasty (TKA).
Knee replacement is most often done in people age 60 and older.
Before the Procedure
Always tell your health care provider what drugs you are taking, including herbs, supplements, and medicines bought without a prescription.
During the 2 weeks before your surgery:
- Prepare your home.
- Ask your doctor which medicines you can still take on the day of your surgery.
- You may be asked to stop taking medicine that makes it harder for your blood to clot. These include aspirin, ibuprofen (Advil, Motrin), naproxen (Naprosyn, Aleve), blood thinners such as warfarin (Coumadin), and other drugs.
- You may need to stop taking any medicines that weaken your immune system, including Enbrel and methotrexate.
- If you have diabetes, heart disease, or other medical conditions, your surgeon will ask you to see the doctor who treats you for these conditions.
- Tell your doctor if you have been drinking a lot of alcohol (more than one or two drinks a day).
- If you smoke, you need to stop. Ask your doctor or nurse for help. Smoking slows healing and recovery.
- Let your doctor know if you get a cold, flu, fever, herpes breakout, or other illness before your surgery.
- You may want to visit a physical therapist before surgery to learn exercises that can help you recover.
- Practice using a cane, walker, crutches, or a wheelchair.
On the day of your surgery:
- You may be told not to drink or eat anything for 6 to 12 hours before the procedure.
- Take the medicines your doctor told you to take with a sip of water.
- Your provider will tell you when to arrive at the hospital.
After the Procedure
You may need to stay in the hospital for 1 to 2 days. Most people are able to go home the day after surgery.
You can put your full weight on your knee right away.
After you return home, you should try to do as much as you can. This includes going to the bathroom or taking walks in the hallways with help. You will also need physical therapy to improve range of motion and strengthen the muscles around the knee.
Most people recover quickly and have much less pain than they did before surgery. People who have a partial knee replacement recover faster than those who have a total knee replacement.
Many people are able to walk without a cane or walker within 3 to 4 weeks after surgery. You will need physical therapy for 4 to 6 months.
Most forms of exercise are OK after surgery, including walking, swimming, tennis, golf, and biking. However, you should avoid high-impact activities such as jogging.
Unicompartmental knee arthroplasty; Knee replacement - partial; Unicondylar knee replacement; Arthroplasty - unicompartmental knee; UKA; Minimally invasive partial knee replacement
Mihalko WM. Arthroplasty of the knee. In: Canale ST, Beaty JH, eds. Campbell's Operative Orthopaedics. 12th ed. Philadelphia, PA: Elsevier Mosby; 2012:chap 7.
Update Date 9/8/2014
Updated by: C. Benjamin Ma, MD, Assistant Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.