Medial Unicompartmental Arthroplasty of the Knee

Jason M. Jennings, MD, DPT; Lindsay T. Kleeman-Forsthuber, MD; Michael P. Bolognesi, MD


J Am Acad Orthop Surg. 2019;27(5):166-176. 

In This Article

Surgical Technique

Surgical exposure of the knee for UKA should be large enough to allow adequate visualization of the knee joint while minimizing medial soft-tissue release. The horizontal tibial bone resection should be minimal, just enough to remove the arthritic surface and be in line with native slope of the tibia. The sagittal tibial cut should be as close as possible to the tibial spine to maximize tibial surface area for the tibial implant without destabilizing the ACL. Penetration of the posterior cortex and making too deep of a tibial cut should be avoided because these errors can result in fracture of the medial tibial plateau. The patient's varus deformity should not be overcorrected because this approach will place excess stress on medial soft-tissue structures resulting in pain and increase contact forces in the contralateral compartment predisposing to increased wear. The tibial component should be sized to maximize the tibial surface area because undersizing can place excess load on the tibial component predisposing to tibial fracture or implant subsidence. Excessive force should be avoided with tibial implant impaction to avoid iatrogenic fracture. Femoral component placement should be in the center (or slightly lateral) on the medial femoral condyle to optimize tracking with the tibial component. Special care should be taken during cementation to optimize interdigitation of the cement in the bone and allow adequate drying time with the knee immobilized. Once cement has hardened, the joint should be thoroughly inspected for presence of retained debris or cement in the posterior aspect of the knee.