Inclusion and exclusion criteria

We enrolled all the patients with a 5-year follow-up who met the classic mUKA selection criteria described by Kozinn and Scott in 1989 [37], i.e., a preoperative mechanical axis deformity of less than 10° in varus or 5° in valgus and a flexion contracture of less than 15°. Further criteria were an intact/competent anterior cruciate ligament, an intact lateral compartment, patellofemoral changes of no greater than grade II or III according to the Albach classification [38], and trochlear wear up to grade IV, provided it presented a central distribution [39].

Patients with primary lateral KOA, a history of complex knee surgery, significant trauma, inflammatory arthropathy, ataxia or neurological disease, psychiatric disorders (or who were in treatment), symptomatic KOA in the contralateral knee, and those who had required bilateral UKA or mUKA revision for aseptic loosening or infection during follow-up were excluded.

All patients provided their signed informed consent.