History and exam

Key diagnostic factors

common

hot, swollen, tender, restricted joint

Almost always present as an indicator of infection.[3][4]

Other diagnostic factors

common

low socioeconomic status

Lower socioeconomic status is associated with a higher frequency of septic arthritis.[24]

history of intravenous drug abuse

Intravenous drug abusers are at risk of introducing staphylococcal organisms.

history of diabetes

Septic arthritis is more common in people with diabetes mellitus.[7]

history of cutaneous ulcers

Cutaneous ulceration provides a portal of entry for pathogenic organisms.

prosthetic joint

Always suspect joint sepsis if a joint prosthesis is present and symptomatic.

Referral to an orthopedic surgeon for further investigation and management is necessary.

Aspirating outside of a sterile operating room is not advised.

history of rheumatoid arthritis or osteoarthritis

An affected joint will have symptoms/signs out of proportion to the disease activity detected in other joints.

The presence of underlying joint disease, such as rheumatoid arthritis or osteoarthritis, is a risk factor for the development of septic arthritis. Up to 35% of cases of septic arthritis will be in abnormal joints.[2]

short history of symptoms

Symptoms have usually been present for <2 weeks at presentation.

Delays in presentation may occur with low-virulence organisms, tuberculosis, or prosthetic infections.[4][5]

fever

Not a reliable indicator of infection.

Present in approximately 60% of cases.[3][4][5][6]

uncommon

history of alcohol use disorder

Septic arthritis is more common in people with alcohol use disorder.[7]

history of previous corticosteroid injection

Very rarely a corticosteroid injection can introduce infection.

Risk factors

strong

underlying joint disease

The presence of underlying joint disease, such as rheumatoid arthritis, osteoarthritis, or crystal arthritides, predisposes the affected joint to the development of infection if pathogens are introduced.[2][3][6][11]

joint prostheses

The presence of prosthetic material increases the likelihood of the development of joint sepsis.[2][11]

immunosuppression

Includes intravenous drug misuse (recurrent needle puncture of the skin to achieve intravenous access increases the likelihood of transfer of pathogenic skin organisms into the bloodstream and subsequent seeding of infection into the joint); diabetes; alcohol misuse; immunosuppressive medication.[3][4][7][11]

contiguous spread (presence of cutaneous ulcers or skin infection)

Can lead to bacteremia and subsequent seeding of infection in a joint.[2][11] The incidence of MRSA is increased in this population.

weak

previous intra-articular corticosteroid injection

Intra-articular corticosteroid injection may be a route through which infection could be introduced into a joint, leading to joint sepsis.[8]

recent joint surgery

Surgery may predispose to local infection.[2][11]

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