This study takes its base in the augmenting number of primary total knee arthroplasty in the world whom quality and survey had permit to widen their indications to younger patients who are in the age of professional activity.

This work will focus on young patients under 55 who had had primary total knee arthroplasty, retrospectively, over the past 10 years, to determine the factors influencing early or late return to work, depending of socio economics factors.

This will optimize the information for the patient, and prepare him if necessary for a long work stop, and possibly obtain a better satisfaction for him.

The primary aim of this study is to determine the rate of young patients returning to work after a primary total knee arthroplasty and the mean delay, and to compare it to other studies.

The mean delay of return to work in the literature is between 8 to 12 weeks, with up to 98% of patients returning to work.

The investigators will next determine which category of patients could have a late return to work superior to 6 months, and also if the surgery could give back a professional activity to patients who were in a long work stoppage.

Inclusion Criteria:

• first intention total knee arthroplasty
• Age at the time of surgery under 55

Exclusion Criteria:

• Not in capacity of completing a questionnaire
• revision of total knee arthroplasty

Patients who underwent a total knee arthroplasty, under 55 at the time of surgery, with or without professional activity at the time of surgery