Acute septic arthritis, infectious arthritis, suppurative arthritis, osteomyelitis, or joint infection is the invasion of a joint by an infectious agent resulting in joint inflammation. Generally speaking, symptoms typically include redness, heat and pain in a single joint associated with a decreased ability to move the joint. Onset is usually rapid. Other symptoms may include fever, weakness and headache. Occasionally, more than one joint may be involved, especially in neonates, younger children and immunocompromised individuals. In neonates, infants during the first year of life, and toddlers, the signs and symptoms of septic arthritis can be deceptive and mimic other infectious and non-infectious disorders.

In children, septic arthritis is usually caused by non-specific bacterial infection and commonly hematogenous, i.e., spread through the bloodstream. Septic arthritis and/or acute hematogenous osteomyelitis usually occurs in children with no co-occurring health problems. Other routes of infection include direct trauma and spread from a nearby abscess. Other less common cause include specific bacteria as mycobacterium tuberculosis, viruses, fungi and parasites. In children, however, there are certain groups that are specifically vulnerable to such infections namely preterm infants, neonates in general, children and adolescence with hematologic disorders, renal osteodystrophy and immune-compromised status. In adults vulnerable groups include an artificial joint, prior arthritis, diabetes and poor immune function. Diagnosis is generally based on accurate correlation between history-taking and clinical examination findings and basic laboratory and imaging findings like joint ultrasound.

In children septic arthritis can have serious consequences if not treated appropriately and timely. Initial treatment typically includes antibiotics such as vancomycin, ceftriaxone or ceftazidime. Surgery in the form of joint drainage is the gold standard management in large joints like the hip and shoulder. Without early treatment, long-term joint problems may occur, such as irreversible joint destruction and dislocation.