Partial Knee Replacements

Unicompartmental knee arthroplasty (UKA) is a reliable treatment modality for osteoarthritis of the knee that is mainly limited to one knee compartment. Isolated medial compartment arthritis is the most common manifestation, which is due to the mechanical axis alignment of the lower extremity that places 60% of weight-bearing forces through the medial compartment in a normally aligned limb. In combination with physical exam, radiographs are the standard imaging modality to aid in diagnosis of isolated knee compartment disease that would benefit from UKA compared to a total knee arthroplasty (TKA). Positioning of the implants in UKA is of the utmost importance. Implants that are too small or do not match the native knee anatomy may lead to instability, while implants that are too large or “over-stuffed” may place excess pressure on the contralateral knee compartment. This excess pressure can cause progressive osteoarthritis of the remaining native compartments and an overall painful knee. Robotic assistance may be utilized for UKA to improve implant positioning compared to conventional, jig-based UKA. Aseptic loosening and progression of arthritis in the previously unaffected knee compartments are the most common complications associated with UKA. Advantages of UKA over TKA include faster recovery and return to function, fewer complications, and maintenance of native unaffected bone and soft tissue anatomy, while presenting only potentially marginally inferior longevity.