As practices had changed by the time this trial was being set up, there was no inclusion in this study.

The urinary elimination kinetics of glucocorticoids after intra-articular injection is very poorly documented. It is estimated that glucocorticoids may be present in the urine up to 6 weeks after intra-articular injection. However, this is not supported by any scientific literature. Despite this lack of evidence, in doping control practice, any presence of glucocorticoids in urine is accepted when the athlete provides evidence of an intra-articular injection that took place less than 6 weeks prior to the doping control. Many doping cases are open to challenge because they are based solely on measurements of prednisolone concentrations and its blood esterase product, prednisone. In order to demonstrate the use of prednisolone for doping purposes (systemic and not intra-articular use), it is therefore necessary to know the urinary elimination kinetics of prednisolone and prednisone, as well as the evolution of the concentration ratio between these 2 molecules.

Inclusion Criteria:

• - Male or female
• 18-65 years old
• requiring intra-articular injection of prednisolone as part of routine care
• naive to any corticosteroid administration
• requiring a blood biology test as part of routine care and before the infiltration procedure
• For women of childbearing age, negative urine pregnancy test at inclusion
• Affiliated to a social health insurance plan
• Able to understand the protocol and give free, informed and written consent

Exclusion Criteria:

• NA

Patient consulting the rheumatology department of the university hospital of Strasbourg (France) for a knee pathology requiring a glucocorticoid infiltration.