ORTHOPEDICS + SPORTS MEDICINE
Partial Knee Replacement
Resurfacing only the damaged compartment, preserving healthy bone, ligaments, and more natural knee motion.
Arthritis does not always affect the entire knee. For some patients, cartilage loss remains confined to one section while the remaining joint surfaces and ligaments continue to function well. Partial knee replacement treats only the damaged compartment, leaving more of the patient’s natural bone, cartilage, and knee structure in place.
Determining whether the damage is truly isolated is the most important part of planning this procedure. Dr. Charles Stewart evaluates the location of pain, leg alignment, ligament stability, knee motion, and imaging before recommending a partial replacement. When the knee meets the necessary criteria, the operation can provide an alternative to resurfacing the entire joint.
The Three Compartments of the Knee
The knee is commonly divided into three compartments:
- The medial compartment on the inner side of the knee
- The lateral compartment on the outer side
- The patellofemoral compartment between the kneecap and femur
Articular cartilage covers the ends of the bones within these compartments. The medial and lateral menisci provide cushioning between the femur and tibia, while ligaments guide and stabilize the joint.
Osteoarthritis may begin in one compartment and remain concentrated there for many years. The medial compartment is affected most often. When the other sections of the knee remain healthy, replacing all of the joint surfaces may not be necessary.
Who May Be a Candidate?
Partial knee replacement, also called unicompartmental knee replacement, is intended for a specific pattern of arthritis. It is not simply a smaller version of total knee replacement that can be chosen based on preference.
A possible candidate generally has:
- Arthritis limited to one knee compartment
- Pain that matches the location of the cartilage damage
- Stable knee ligaments
- Adequate knee motion
- A deformity that can be corrected
- Limited inflammation in the remaining compartments
Inflammatory arthritis or widespread cartilage loss may make total knee replacement more appropriate. Significant ligament damage, severe stiffness, or a fixed deformity can also affect candidacy.
Age alone does not determine whether a patient qualifies. The decision depends more heavily on the condition and mechanics of the knee.
Confirming Where the Arthritis Is Located
The orthopedic assessment includes a discussion of when and where the knee hurts. Pain isolated to the inner or outer side may suggest unicompartmental arthritis, but symptoms alone are not enough to select surgery.
During the examination, the specialist assesses motion, ligament stability, tenderness, and leg alignment. X-rays taken from multiple angles show which joint spaces have narrowed and whether arthritis is present elsewhere in the knee.
Stress X-rays or other imaging may occasionally be used to evaluate the preserved compartments and determine whether a deformity remains flexible. The final condition of the cartilage and ligaments is also confirmed during surgery. If damage is more extensive than expected, conversion to a total knee replacement may be necessary.
What Is Replaced During the Procedure?
During partial knee replacement, the surgeon removes damaged cartilage and a small amount of bone from the affected side of the joint. The healthy compartments are left intact.
A metal component covers the prepared surface of the femur, and another component is positioned on the tibia. A medical-grade plastic insert between them provides a smooth surface for movement. The major ligaments within the center of the knee are usually preserved.
Retaining healthy structures may allow the reconstructed knee to maintain more of its natural motion and sensation. The smaller area of surgical work can also mean less disruption to bone and soft tissue than occurs during a total knee replacement.
However, the quality of the result still depends on accurate alignment, ligament balance, and appropriate patient selection.
Partial Vs. Total Knee Replacement
A total knee replacement resurfaces the medial, lateral, and usually patellofemoral areas as needed. A partial replacement treats only one damaged compartment.
Potential advantages of a partial procedure may include:
- Preservation of more natural bone and cartilage
- A smaller incision
- Less blood loss
- Earlier return of knee motion
- A knee that may feel more natural during movement
These advantages must be weighed against the possibility that arthritis can later develop in the unreplaced areas. A partial replacement may eventually need to be converted to a total knee replacement if the remaining joint deteriorates or the components fail.
The best operation is the one that matches the actual extent of the disease. Preserving an arthritic compartment simply to perform a smaller procedure would not provide an appropriate reconstruction.
Early Recovery
Partial knee replacement may be completed on an outpatient basis or with a short hospital stay. Patients begin standing and walking with assistance soon after surgery.
A walker, crutches, or a cane may be used initially. Some patients progress away from an assistive device sooner than they would after total replacement, but this varies with strength, balance, pain, and overall health.
Swelling and soreness are expected during early healing. Patients receive instructions for incision care, medication, activity, and blood-clot prevention. Cold therapy and elevation may help manage swelling after walking or exercise.
Physical Therapy After Surgery
Physical therapy works to restore knee motion, leg strength, and a normal walking pattern. Because the central ligaments and healthy compartments remain, many patients can begin functional movement relatively early.
Rehabilitation may include:
- Straightening and bending the knee
- Activating the quadriceps
- Improving hip and leg strength
- Walking with decreasing support
- Practicing stairs
- Rebuilding balance and endurance
Patients can often return to basic daily activities within several weeks, although complete recovery takes longer. Driving and returning to work depend on which knee was treated, medication use, and the physical demands involved.
Walking, swimming, cycling, golf, and other low-impact activities are generally better suited to a knee replacement than repetitive running or jumping.
When to Ask About Partial Knee Replacement
An evaluation may be appropriate when pain remains concentrated on one side of the knee and no longer responds adequately to medication, injections, activity changes, or physical therapy.
Patients should not assume that localized pain automatically makes them candidates. Meniscus tears, ligament injuries, tendon problems, and kneecap disorders can also cause pain in one area. A complete assessment is needed to confirm that isolated arthritis is responsible.
Summary
Partial knee replacement offers a focused solution when arthritis is limited and the rest of the joint remains functional. Its success depends on selecting the right knee for the procedure rather than simply choosing the least extensive operation.
Dr. Charles Stewart assesses the entire joint before determining whether its healthy structures can be preserved. This careful distinction helps patients understand whether partial or total knee replacement better matches their condition and long-term needs.