Late recurrence of varus deformity after proximal tibial osteotomy. One hundred thirteen knees with medial gonarthrosis in 95 patients were treated by valgus-producing proximal tibial osteotomy and followed clinically and roentgenographically for a minimum of five years (mean, 6.3 years). Sixty-four knees (57%) were pain free or had only mild discomfort when walking. The standing femorotibial angle decreased from a postoperative average of 9.3 degrees valgus to 7.8 degrees valgus at the final follow-up examination. The tendency for varus recurrence greater than 5 degrees and for medial- or lateral-compartment arthritic progression was evaluated using the Kaplan-Meier survival method. Varus recurred in 18%, lateral-compartment arthritic progression in 60%, and medial-compartment arthritic progression in 83% by nine years after surgery. The probability of arthritic progression is much higher than the probability of significant varus recurrence in long-term roentgenographic follow-up studies of patients with valgus-producing proximal tibial osteotomies. 