If your arthritis or injury is limited to only one side of the knee, partial knee replacement may be an option for you. During a partial knee replacement (also known as unicompartmental knee replacement), only the damaged side of the knee is replaced with prosthetics, and healthy bone remains.
The knee is made up of three compartments including the medial compartment (the inside part of the knee); the lateral compartment (the outside part of the knee); and the patellofemoral compartment (the front of the knee between the kneecap and the thigh bone). If you have advanced osteoarthritis or a knee injury that is limited to a single compartment of the knee, you may be a candidate for partial knee replacement.
During the procedure, the damaged compartment is replaced with metal and plastic, and the healthy cartilage, bone, and ligaments are preserved.
You would not be a candidate for partial knee replacement if you have any of the following characteristics:
- Inflammatory arthritis
- Significant knee stiffness
- Ligament damage
For patients undergoing a partial knee replacement, the advantages over a total knee replacement include:
- Quicker recovery
- Less pain after surgery
- Less blood loss
- More flexibility in the knee (may bend better)
- Feels more like a normal knee (as healthy cartilage, bone, and ligaments are preserved)
- Retains more natural function of the knee
Partial knee replacement allows for quicker recovery times and less pain in recovery when compared to a total knee replacement, as the partial knee replacement is done through a smaller incision. Because the procedure is less invasive, patients usually spend less time in the hospital and return to normal activities sooner than total knee replacement patients.
The disadvantages of partial knee replacement as compared to a total knee replacement include:
- Slightly less predictable pain relief
- Need for more surgery in the future (if arthritis develops in other compartments of the knee)
During your consultation, Dr. Mirza will determine whether or not you are a candidate for partial knee replacement.
Medical History
Dr. Mirza will ask you several questions about your medical history, including questions about your knee pain and where it is, and your ability to function.
The location of your pain is an important determining factor. If the pain is located entirely on the inside portion or outside portion of the knee, you may be a candidate for this procedure. If your pain radiates throughout your entire knee or in the front of your knee (under your kneecap), you may be a better candidate for total knee replacement.
Physical Examination
During your physical exam, Dr. Mirza will closely examine your knee to determine the location of your pain. He will also test your knee for range of motion and ligament quality. If your knee is too stiff or if your knee ligaments feel weak or torn, then he will not recommend partial knee replacement surgery for you and may recommend a total knee replacement surgery instead.
Imaging Tests
Dr. Mirza will order several x-rays of your knee to see the pattern of arthritis or knee injury. These images will determine the extent of damage and deformity in your knee. For some patients, he may order magnetic resonance imaging (MRI) scans for a better image of the cartilage.
After your consultation, Dr. Mirza will let you know whether or not you are a candidate for partial knee replacement. If you are a candidate, your surgery will be scheduled accordingly.
You will be scheduled for a preoperative clinic visit at least 1 month prior to your surgery date. This is time for you to review the procedure with Dr. Mirza and to have any of your questions answered.
During your preoperative visit, Dr. Mirza will discuss your options for anesthesia, as well as the need for a contingency plan. If at the time of your surgery, Dr. Mirza discovers that the extent of cartilage damage you have is more than what was expected, then the contingency plan will be to convert your procedure to a total joint replacement.
On the day of surgery, you will be admitted to the hospital.
A doctor from the anesthesia department will discuss anesthesia choices with you. You may choose to have either General Anesthesia where you are put to sleep or you can have a Spinal where you are awake but your body is numb from the waist down.
Before surgery, Dr. Mirza will come to see you and mark your surgical site with a marker.
Surgical Procedure
Dr. Mirza will inspect the joint and make an incision at the front of your knee and then explore the three compartments of your knee to verify that the cartilage damage is limited to one compartment and that your ligaments are intact.
Once verified, Dr. Mirza will proceed with the partial knee replacement, which involves three basic steps:
- Preparing the bone with special saws to remove the cartilage from the damaged compartment of your knee.
- Positioning the metal implants in the place of the removed cartilage and bone, recreating the surface of the joint. Cement may be used to hold the metal parts to the bone.
Inserting a spacer between the two metal components to create a smooth gliding surface.
Recovery Room
You will be taken to the recovery room after your procedure and closely monitored as you recover from the anesthesia. From there, you will be taken to your hospital room.
Typically, a partial knee replacement procedure takes between 1 to 2 hours.
After the operation, most patients are in the hospital for 1 to 3 days. Some patients, however, may be discharged the same day of surgery. The recovery period is shorter than for a total knee replacement, because patients experience less postoperative pain, less swelling, and have easier rehabilitation.
You should be able to return to your normal activities within 6 weeks after surgery.
Pain medication is prescribed for you to help you feel as comfortable as possible. Dr. Mirza may prescribe opioids (narcotics), non-steroidal anti-inflammatory drugs or local anesthetics to help control pain. It is important that you follow your doctor’s instructions regarding opioids. Narcotics can be addictive, so you should stop taking these medications as soon as your pain is tolerable without them.
Physical therapy is an important part of your rehabilitation. A physical therapist will give you exercises to help maintain your range of motion and restore your strength.
Follow up visits will be scheduled for you at regular intervals to assess your recovery and rehabilitation.
You can begin putting weight on your knee immediately after surgery, although you may need a walker, cane, or crutches for support for the first several days or weeks until you are comfortable enough to walk without assistance.
With the right patient selection, partial knee replacements have demonstrated excellent to medium long-term results in both younger and older patients.
Partial Knee Replacement Surgery in Portland, Oregon
Our knee replacement surgeon, Dr. Mirza, has training in adult arthritis and joint replacement surgery. His practice focuses on personalized care for patients of all ages seeking to reduce pain, improve function and return to active lifestyles. Dr. Mirza is board-certified by the American Academy of Orthopaedic Surgeons (AAOS) and is vice president of the Oregon Association of Orthopaedic Surgeons (OAOS).
If you think partial knee replacement surgery may be right for you, please call our office at 503-850-9940 to request an appointment.
