The optimal duration of systemic antibiotic administration for native joint septic arthritis is unknown. The investigators perform a randomized study allowing up to 3 surgical lavages and allocating patients into a two-week's and a four week's randomization arm

The optimal duration of systemic antibiotic administration for native joint septic arthritis is unknown. The investigators perform a randomized study allocating patients into a two-week's and a four week's randomization arm.

The adult patients are hospitalized for septic arthritis. A computer program randomizes 1:1 between a two week's and a four week's arm of targeted antibiotic treatment of which at least the first week is intravenously. The randomization may occur until Day 5 of admission. Up to three surgical interventions are allowed. The investigators allow the inclusion of all bacterial arthritis and all joints.

Inclusion Criteria:

1. Age >17 years
2. Microbiologically-confirmed septic arthritis
3. At least one surgical drainage/lavage

Exclusion Criteria:

1. Presence of osteosynthesis material in the vicinity of the articulation
2. Presence of a concomitant infection needing more than 2 week's of antibiotic therapy
3. More than 3 surgical drainages
4. Life expectancy less than 6 months
5. Chronic osteomyelitis in vicinity of the arthritis