Both MacIntosh and McKeever reported positive results, but neither’s results could be replicated consistently enough to be deemed successful. In 1972, MacIntosh published his results and saw an 80% success rate for osteoarthritic knees and only a 69% success rate for rheumatoid knees (Table 1.1;I). Early historical reports of UKA survivorship exhibited varying degrees of success, resulting in many surgeons abandoning the procedure as a treatment for isolated compartmental joint arthritis.

Historically, selection criteria for UKA were nonexistent, and no official consensus was available to guide surgeons. Essentially, there were believers and nonbelievers in the procedure, with no definitive algorithms available for determining appropriate candidates. Kozin and Scott developed the first widely adopted set of indications and contraindications for UKA in the late 1980s. Such criteria were held steadfast until recently, when there has been a challenge to expand the indications for UKA. While some surgeons may now recommend UKA in patients with ACL-deficient knees or patellofemoral arthritis , there remains relatively strong opposition that ascribes to the stricter indications outlined by Kozin and Scott et al. (Table 1.2) [13]. Following these relatively stringent parameters, Ritter et al. found that 4.3% out of 4021 knee arthroplasties met the indications for UKA, while 6.1% were appropriate candidates for UKA based on surgical pathology assessments [25]. These numbers are relatively consistent with current rates of UKA in the United States; however, there are centers driving these numbers up with rates as high as 20–30%.