The incidence of indications for hip and knee arthroplasty is constantly increasing due to an increase in arthrogenic risk factors and life expectancy.

In younger patients, with a higher functional demand, resumption of physical activity and sport is a major objective after resumption of walking and pain management.

The repercussions of returning to sports after arthroplasty have been widely studied in the literature.

Few studies have looked specifically at high-impact activities, the possibility of resuming sport and its consequences. The recommendations are essentially based on expert opinion.

The incidence of indications for hip and knee arthroplasty is constantly increasing due to an increase in arthrogenic risk factors and life expectancy. Projections predict an increase in the number of prosthetic surgeries between 2020 and 2030 of 150% for total hip replacements (THR) and 230% for total knee replacements (TKR).

In younger patients, with a higher functional demand, resumption of physical activity and sport is a major objective after resumption of walking and pain management. They are also more likely to resume physical activities with high peak joint stresses, known as "high-impact sports", most often against the advice of their surgeon.

The repercussions of returning to sports after arthroplasty have been widely studied in the literature. These are essentially descriptive cross-sectional studies which show greater participation in low or medium impact sports activities in patients with prostheses.

Few studies have looked specifically at high-impact activities, the possibility of resuming sport and its consequences. The recommendations are essentially based on expert opinion.

Concerning trail running, a discipline in full expansion, particularly in the longest formats; a single study in 2019, involving 18 runners with a prosthesis, did not reveal any specific constraints compared to healthy runners during a 170 km ultratrail.

Inclusion Criteria:

• Trail runner (declarative)
• Having been operated for a hip or knee arthroplasty
• No limit to the length of time or volume of trail riding

Exclusion Criteria:

• Refusal to participate
• Trailer not understanding French

The recruitment process will involve a pre-recruitment informing runners that we are looking for trail runners of all levels who have undergone hip and knee replacement surgery. This information will be disseminated via social networks, trail clubs, and via the organisers of major trail races (Diagonale des Fous, UTMB). We will then send the questionnaires to all the runners who have replied to us and mentioned their willingness to participate in the study.