['Valgus high tibial osteotomy (HTO) is an established procedure for the medial gonarthrosis. In several studies, many negative influencing factors were evaluated. However, until now, the factor "age" was examined only insufficiently. The aim of our study was to evaluate the factor age in predicting the functional outcome after HTO, and we hypothesized that valgus HTO leads to equal results in the treatment of varus osteoarthritis independent of the patient\'s age.', 'We could generate 13 pairs of patients with a median age at operation of 57 (55-63) years (group A) versus patients 15\xa0years younger with a median age of 42 (39-47) years (group B). The patients were matched according to the following criteria: age, gender, operation/osteosynthesis method, body mass index, same additional operations, and follow-up time. Evaluation of the patients was done by use of the Tegner and Lysholm score and visual analogue scale (VAS) as well as by subjective satisfaction of the patients.', 'The Lysholm score showed a significant improvement in group A from 41 (SD\xa0±\xa012.3) to 65 (SD\xa0±\xa023.8) points (p\xa0=\xa00.01) and in group B from 33 (SD\xa0±\xa016.7) to 70 (SD\xa0±\xa031.8) points (p\xa0=\xa00.007). Moreover, the VAS decreased significantly in group A from 77 (SD\xa0±\xa015.3) to 36 (SD\xa0±\xa021.3) points (p\xa0=\xa00.003) and in group B from 73 (SD\xa0±\xa022.7) to 41 (SD\xa0±\xa033.7) points (p\xa0=\xa00.02). However, there was no significant difference for both groups regarding the activity of the patients evaluated by the Tegner score (group A: preop.: 5 (1-9), follow-up: 3.5 (1-6); group B: preop.: 6 (3-9), follow-up: 4 (2-7)). Furthermore, there was no significant difference between both groups in view of the Lysholm, Tegner and VAS.'] Does age influence the clinical outcome after high tibial osteotomy?