What Is a Unicompartmental Replacement?
The knee has three compartments — medial (inner), lateral (outer), and patellofemoral (front). When arthritis is confined to a single compartment, it is possible to replace only that worn area rather than resurfacing the entire joint. The healthy cartilage, ligaments (including the cruciate ligaments), and bone of the other compartments are left completely intact.
The medial compartment is affected most commonly and accounts for the majority of unicompartmental replacements. Lateral and patellofemoral unicompartmental replacements are performed less frequently but remain effective options for appropriately selected patients.
Advantages over Total Knee Replacement
- Smaller incision and less soft tissue disruption
- Bone stock preserved — facilitates conversion to total knee replacement if required
- Retains the ACL and natural knee kinematics for a more normal feel
- Faster recovery and shorter hospital stay
- Lower rates of early complications
Important Considerations
- Strict patient selection is required — the remaining compartments and ligaments must be intact
- Long-term survival rates are slightly lower than total knee replacement in some studies
- Disease progression in other compartments may eventually necessitate conversion to total replacement
Patient Selection
Careful patient selection is the most important determinant of a successful outcome. Not all patients with medial compartment arthritis are suitable candidates.
- Arthritis confined to a single compartment on weight-bearing X-rays and MRI
- Intact anterior cruciate ligament (ACL) — this is essential to normal unicompartmental knee function
- Minimal varus or valgus deformity (usually less than 15 degrees) that is passively correctable
- Absence of significant inflammatory arthritis
- Body weight within acceptable limits — extreme obesity increases the risk of implant failure
The decision between unicompartmental and total knee replacement requires detailed discussion and careful review of your imaging. Dr. Pirpiris will advise which approach is most appropriate for your specific anatomy and disease pattern.
Recovery
Recovery from unicompartmental replacement is generally faster than after a total knee replacement. Many patients are discharged home within one to two days and are walking with minimal or no aids within two to three weeks. Most return to driving within four weeks and to recreational activities by two to three months.
The rehabilitation programme focuses on regaining knee flexion and strength. Because the other compartments and the cruciate ligaments are preserved, the knee often feels more natural than after a total replacement.
Discuss Partial Knee Replacement
For a personalised assessment and treatment plan, contact Dr. Pirpiris’s rooms at Cabrini Medical Centre, Malvern.
📞 Call 03 9508 9600