Ultrasonography Assessment of Septic Arthritis on Native Joint

"All patients will be seen at day 0, day 4, day 15 and at 3 months. These visits are usually programmed. Only monitoring ultrasonography, a non invasive exam, and self-administered questionnaires will be made, additional to standard exams for all patients included (no control group).~Day 0 :~* Information of patient and no opposition getting~* Clinical exam~* Laboratory tests~* Radiography of the targeted joint~* Ultrasonography of the targeted joint and controlateral joint (about 20 minutes)~Day 4 :~* Clinical exam~* Laboratory tests~* Ultrasonography of the targeted joint and controlateral joint (about 20 minutes)~Day15 :~* Clinical exam~* Laboratory tests~* Ultrasonography of the targeted joint and controlateral joint (about 20 minutes)~M3 :~* Clinical exam~* Laboratory tests~* Radiography of the targeted joint~* Ultrasonography of the targeted joint and controlateral joint (about 20 minutes)~* Functional outcome"