Partial Knee Replacement

If you are considering knee surgery, the following partial knee replacement information may help you understand your alternatives.

Knee pain from arthritis can be particularly debilitating because we use our knees in almost all of our daily activities. If you are experiencing severe knee pain that interferes with your normal functioning, your doctor may recommend a partial knee replacement, also known as uni-compartmental knee replacement.

This procedure is much less invasive than total knee replacement and may give relief to people suffering from arthritis of the knee or a knee injury. Partial knee replacement surgery replaces only the damaged area of your knee joint, may require only one day of hospitalization, and results in dramatically less recovery time when compared with total knee replacement surgery.

The knee can be divided into three compartments: the medial compartment, the lateral compartment, and the patello-femoral compartment. The uni-compartmental implant is designed to replace either the medial or lateral compartment.

A pair of x-rays showing painful

bone-on-bone contact.

Uni-compartmental Osteoarthritis

The x-ray far left shows a right leg with a degenerated medial (inside) compartment and no space between the femur and the tibia. This bone on bone contact can be quite painful.

Post-operative View with Implant

The x-ray near left shows a right leg with a degenerated medial (inside) compartment and no space between the femur and the tibia. This bone on bone contact can be quite painful.

Available Treatment Options

Your doctor may try several conservative treatments before recommending partial knee replacement.

If the conservative treatments do not relieve your pain from arthritis of the knee, surgical procedures may be recommended. Arthroscopic surgery is a minimally invasive procedure to remove debris or repair torn cartilage. Total knee replacement surgery is major surgery that replaces all three compartments of the knee. Between those two alternatives is uni-compartmental surgery.

Minimally Invasive Partial Knee Replacement

The uni-compartmental knee replacement is a less invasive option for patients with knee arthritis that is isolated to either the medial or lateral compartment of the knee. This minimally invasive procedure provides several benefits to patients who have a moderately active lifestyle, are within normal weight ranges, and have arthritis that is confined to a single compartment.


There are many benefits to uni-compartmental knee replacement.

First of all, the procedure leaves a 3-4 inch incision, compared to an 8-12 inch incision for total knee replacement.

There is no disruption of the knee cap, which leads to more rapid rehabilitation.

There is minimal blood loss in a partial knee replacement. The procedure causes less post-operative pain and requires greatly reduced hospitalization compared to a total knee replacement.

There is also a reduced need for anesthesia and post-operative medication.

After the surgery, patients are able to walk within 3 to 4 hours and experience a much faster rehabilitation and recovery (2 to 5 weeks for many patients).

After achieving full recovery, most patients experience an increased range of motion when compared to total knee replacement.

Pre-operative Testing and Consultation

You and your orthopedic surgeon participate in an initial surgical consultation. This appointment may include preoperative X-rays, a complete medical and surgical history, physical examination, and comprehensive list of medications and allergies. During this visit, your orthopedic surgeon will review the procedure and answer any questions you may have.

Pre-operative Class

Taught by the multidisciplinary total joint team, this class provides detailed information regarding all phases of your joint replacement experience. Members of the orthopaedic surgical, nursing, physical therapy, and discharge planning staff answer any questions that you might have regarding your joint replacement plan of care. It is highly recommended that you make plans to attend a preoperative class. They are offered weekly and take place on the post operative orthopaedic surgical floor in the hospital so you will have a chance to become familiar with your post op surroundings. You are encouraged to bring someone with you who will be assisting you after your surgery on your return home.

Your orthopedic surgeon may ask you to consult a physical therapist to discuss the recovery period, rehabilitation program, and important precautions, as well as instruct you in exercises that you can begin prior to surgery that will make the recovery much easier.

Finally, maintaining good physical health prior to surgery will also improve the recovery period and overall post-operative outcome.

Preparation for the Hospital

You may want to bring the following items to the hospital for your knee replacement surgery:

Clothing: underwear, socks, t-shirts, exercise shorts for rehabilitation.

Footwear: walking or tennis shoes for rehab; slippers for hospital room.

Walking aids: walker, cane, wheelchair, or crutches if used prior to surgery.

Insurance information

You should follow your regular diet on the day before your surgery. Do not eat or drink after midnight. Follow your doctor’s instructions regarding use of medication in the days leading to surgery. Finally, try to get a long, restful night’s sleep.

Day of Surgery

On the morning of the surgery, you will be admitted to the hospital and taken to the appropriate pre-surgical area. The nurse will spend a few minutes preparing you for surgery by taking your vital signs, starting IV fluids, and administering medications as needed. You will be asked to empty your bladder just prior to surgery, and to remove all jewelry, contacts, dentures, etc. You will change into a hospital gown, be placed on a stretcher, and transported to the operating room. The anesthesiologist will meet you and review the medications and procedures used during the surgical case.

The Procedure

Anesthesia will be either general or spinal. With a general anesthetic you are asleep and with a spinal your legs and hips are numb allowing you to have the operation without pain. Patients who receive spinal anesthesia are given intravenous medication during the procedure to allow them to remain comfortable and relaxed.

The partial knee replacement procedure begins with the exposure of the joint through a 3 to 4 inch incision. The surgeon then properly balances the knee joint. Next the end of the femur and top of the tibia are shaped to accommodate the uni-compartmental knee replacement components. Trial components are placed on the bones to ensure proper alignment and are removed once this alignment is achieved. At this point the femoral and tibial components are implanted, the incision is closed and the procedure is complete.

Returning Home

You will be discharged when you can get out of bed on your own and walk with a walker or crutches, walk up and down three steps, bend your knee 90 degrees and straighten your knee.

You’ll continue your home exercise program and go to outpatient physical therapy, where you will work on an advanced strengthening program and such programs as stationary cycling, walking, and aquatic therapy.

Your long-term rehabilitation goals are a range of motion from 100-120 degrees of knee flexion, mild or no pain with walking or other functional activities, and independence in all activities of daily living.

Click here for information on risks of knee replacement surgery

Click here for information on rehabilitation after knee replacement surgery

Link to The American Academy of Orthopaedic Surgeons