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

Traditional Indications

The primary indications for UKA are isolated anteromedial osteoarthritis or spontaneous osteonecrosis of the knee. When UKA was first introduced in the 1970s, it was associated with high rates of early failure.[6] In 1989, Kozinn and Scott[7] established indications for patient selection which included age lower than 60 years, weight under 180 pounds, avoidance of heavy labor, minimal baseline pain, preoperative arc of motion of 90° with less than a 5° flexion contracture, and angular deformity under 15°. Contraindications included osteoarthritis of the patellofemoral joint (PFJ) or contralateral condyle, inflammatory arthropathy, presence of chondrocalcinosis, and cruciate ligament insufficiency.[7]

Adherence to traditional indications limited the pool of eligible patients, with one study finding only 6% of patients meeting all parameters.[8] Others have argued that over 50% of patients undergoing TKA should be considered for UKA.[9] Hamilton et al[9] found that 68% of their 1,000 patients who underwent UKA had one or more of the previously cited contraindications. No differences were noted in pain or functional scores at 10 years between those with one or more contraindications and "ideal" candidates.[9] Interestingly, more patients in the "ideal" candidate group had poor functional scores at 10 years compared with those with contraindications (18% versus 7%). Implant survival at 15 years was 90.7% in the "contraindicated" group and 88.5% in the "ideal" group, with no difference in mechanism of failure or time to revision.[9]