Septic Arthritis

Septic arthritis is a bacterial infection within a joint, causing rapid-onset pain, swelling, and reduced movement. It is a medical emergency because delayed treatment can permanently damage the joint.

• Sudden onset of severe pain in a single joint, most often the knee
• Significant swelling, warmth, and redness over the affected joint
• Marked reduction in range of motion, with pain on any attempted movement
• Fever and feeling generally unwell
• In infants and young children, refusal to move the affected limb or bear weight

• Bacteria reach the joint either through the bloodstream from an infection elsewhere in the body, through direct spread from a nearby bone infection, or through a penetrating injury or medical procedure involving the joint.
• Staphylococcus aureus is the most common cause.
• Risk is increased in young children, older adults, people with pre-existing joint disease, diabetes, or a weakened immune system, and those with a prosthetic joint.

• Suspected clinically based on the rapid onset of a hot, swollen, painful joint, especially with fever.
• Joint aspiration (removing fluid from the joint with a needle) for laboratory analysis, including cell count, Gram stain, and culture, is the key diagnostic step and should be done urgently wherever this can be performed safely.
• Blood tests (such as inflammatory markers and blood cultures) support the diagnosis and help identify the causative organism.

Septic arthritis is a medical emergency requiring hospital-level care. Prompt joint drainage — either by repeated needle aspiration or surgical washout — is essential to remove infected fluid and reduce joint damage.

Intravenous antibiotics are started as soon as joint fluid has been sampled, initially chosen empirically to cover the most likely organisms and later adjusted according to culture results.

Antibiotic treatment typically continues for several weeks, often starting intravenously and transitioning to oral medicine as the infection improves.

Physiotherapy is introduced once the acute infection is controlled to help restore joint movement and function.

• Seek prompt medical care for any joint that suddenly becomes hot, swollen, and severely painful, especially with fever.
• Ensure proper wound care and prompt treatment of skin infections, which can spread to a joint.
• Manage underlying conditions such as diabetes well, as they increase infection risk.
• Seek urgent assessment for any injury involving a joint, particularly if there is a wound near the joint.