The results of 73 total knee arthroplasties in 67 patients after a high tibial osteotomy (HTO) were carefully reviewed at an average follow-up period of 73 months (range, 24-132 months). An extensive clinical as well as radiographic review was performed in an attempt to evaluate parameters that might portend more favorable or worse outcomes. Additional comparisons were made with two groups of 73 primary TKAs matched according to age, gender, diagnosis, prosthetic fixation, and length of follow-up period. The two comparison groups differed in that one (Group A) was additionally matched to deformity before TKA with a second comparison group (B) matched to pre-HTO deformity. On the basis of a 100-point knee rating scale, 36% of the study group patients had either a fair or poor result or required additional surgery. This was significantly greater than either comparison group (p < 0.01). Factors that prognosticated a worse outcome in the HTO patients (p < 0.01) included (1) workmen's compensation patient, (2) history of reflex sympathetic dystrophy after HTO, (3) early onset (less than one year) or no period of relief of pain after HTO, (4) multiple surgeries before HTO, and (5) an occupation as a laborer.