BASICS

DESCRIPTION

• Infectious inflammation of synovial space that can affect any joint.
• In children, more commonly progresses to osteomyelitis because of presence of intracapsular metaphyses.

RISK FACTORS

• Recent fractures or injuries can provide an entry point for infection.
• Consider gonococcal arthritis in sexually active patients.

PATHOPHYSIOLOGY

• Infectious agents enter joint space allowing for infection. Infection can easily spread to adjacent bone in children with intracapsular metaphyses.

ETIOLOGY

• A variety of of organisms are implicated, including Staph aureus, coagulase negative staphylocci (associated with implants and prostheses), enteric organisms (associated with gastrointestinal infections).

COMMONLY ASSOCIATED CONDITIONS

• Sickle cell disease associated with salmonella osteomyelitis as well as Strep pneumo arthritis

DIAGNOSIS

HISTORY

• Acute onset of fever and joint pain, swelling and limited range of motion.

PHYSICAL EXAM

• Fever and malaise
• Hip: No swelling palpable. May notice asymmetry of gluteal fold.
• Other joints: swelling, warmth, redness and tenderness at affected joint. Limited range of motion.
• Pain with compression of joint spaces.
• Usually only one joint involved. Involvement of multiple joints argues against septic arthritis.

DIAGNOSTIC TESTS & INTERPRETATION

Lab

Initial Lab Tests

• CBC demonstrates increased WBC
• ESR elevated
• CRP has high negative predictive value
• Blood culture

Imaging

• Xray to rule out occult fracture and to look for periosteal reaction.
• Ultrasound, especially of hip joint, to determine presence of effusion.
• MRI to look for surrounding osteomyelitis in joints with intracapsular metaphyses (elbow, hip, shoulder, ankle)

Diagnostic Procedures / Other

• Synovial fluid aspiration necessary, but not particularly sensitive or specific. Send for WBC and culture (requires special culture or PCR testing for Kingella)

Pathological Findings

DIFFERENTIAL DIAGNOSIS

• Occult fracture
• SCFE, avascular necrosis
• Autoimmune or viral Arthritis
• Cellulitis overlying a joint

TREATMENT

MEDICATION

First Line

• Antibiotics: tailored to specific organisms. If no risk factors identified, most likely Gram positive cocci.

SURGERY / OTHER PROCEDURES

• Surgical wash out

DISPOSITION

Admission Criteria

• Critical care admission criteria
• Requires admission for IV antibiotics and surgical wash out

Discharge Criteria

• Arrangements for prolonged IV antibiotic course

Issues For Referral

• Requires emergent orthopedic consultation secondary to risk for long term disability

FOLLOW UP

FOLLOW-UP RECOMMENDATIONS

• Discharge instructions and medications
• IV antibiotics until afebrile x 24 hours
• Activity
• Physical therapy for rehabilitation of joint

PROGNOSIS

• Early diagnosis and wash out may prevent long term disability in affected joint

COMPLICATIONS

• Osteoarthritis or mobility loss from joint erosion
• Sepsis

See Also (Topic, Algorithm, Electronic Media Element)

• Kocher criteria

CODES

ICD9

• PUBLISHER WILL ENTER

SNOMED

• PUBLISHER WILL ENTER

PEARLS AND PITFALLS

• In neonates may present with multiple joint involvement and systemic illness as is usually blood-borne.
• If high suspicion for septic arthritis, patient should be treated regardless of synovial fluid results.