Function and sport participation was analyzed via a self-administered questionnaire in 347 patients with unilateral noncomplicated TKA. It was 227 women and 120 men with a mean age of 75 (range, 28 to 94) and a mean follow-up of 44 months (range 13-71). Two hundred and thirty-seven patients (68%) reported that their knee was "normal", 56% that their activities were limited by their knee, and 66% that they were as active as they expected to be before the intervention. Of them, 98% were satisfied. Of the patients who were insufficiently active, 52% were not satisfied with their outcome (P < 0.0001). Neither the duration of preoperative pain, the age at evaluation or the number of previous surgeries influenced the subjective result or the degree of patient satisfaction. Among patients under 75 years, 10% regularly participated in strenuous sports but only 13% felt that this ability was important. When participation was analyzed in the motivated patients subgroup, 63% regularly took part in at least one impact sport.