Osteomyelitis and septic arthritis

Also called Bone infection, Joint infection, Septic arthritis

Infection in a bone or a joint. A hot, swollen, exquisitely painful joint is an emergency, and every hour of delay destroys cartilage.

What it is

Infection of bone, called osteomyelitis, or of a joint, called septic arthritis.

**Septic arthritis is the emergency.** Bacteria inside a joint destroy cartilage within hours to days, and the damage is permanent. A hot, swollen, extremely painful joint that the person will not move needs the joint aspirated and antibiotics started urgently, usually the same day. Delay causes lifelong disability and, in the frail, death.

The trap is that it looks like gout or a flare of rheumatoid arthritis. Both are common, both cause hot swollen joints, and the only way to tell is to aspirate the joint and look. A person with rheumatoid arthritis on immunosuppressive treatment is at higher risk of septic arthritis, not lower, and their flare may be an infection.

Osteomyelitis develops more slowly. In adults it usually follows a wound, surgery, or a diabetic foot ulcer that has reached bone. In children it is usually bloodborne and presents with limp, pain and fever.

A foot ulcer that probes to bone in someone with diabetes is osteomyelitis until proven otherwise, and it is a leading route to amputation.

Treatment is long: weeks of antibiotics, often intravenous, and frequently surgery.

Signs you might notice

Septic arthritis: a single joint that is hot, swollen, red and severely painful; refusal or inability to move it; fever; feeling unwell. In children, a limp or refusal to weight bear, or a baby who will not move a limb.

Osteomyelitis: persistent deep bone pain, tenderness, swelling and warmth over the area; fever; and in chronic cases, a discharging sinus.

In a diabetic foot: an ulcer that has not healed, that is deep, or that you can touch bone through with a sterile probe.

999 or A and E now: a hot, swollen, very painful joint, especially with fever, and especially in a child, an older person, or anyone immunosuppressed or with a joint replacement.

An infected joint replacement is a specific emergency and needs the original surgical team involved.

How it can affect day-to-day life

The most common failure is attributing a hot joint to gout without aspirating it, particularly in someone who has had gout before. Having gout does not protect against infection.

Immunosuppressed people, on steroids, biologics or chemotherapy, may have far less fever and less dramatic findings while having a serious infection.

In children a limp with fever is an emergency, and irritable hip, a common self-limiting condition, cannot be distinguished from septic arthritis without assessment.

Treatment involves weeks of intravenous antibiotics, often at home through an outpatient service, with a line that needs care and carries its own risks.

For diabetic foot osteomyelitis, the decision between prolonged antibiotics and surgery is specialist, and getting to a multidisciplinary diabetic foot service quickly changes outcomes.

Recovery of joint function afterwards needs physiotherapy and is often prolonged.

Supporting someone well

Treat a hot, swollen, painful joint as septic arthritis until proven otherwise. Same day, A and E.

Insist on aspiration before assuming gout, particularly with fever.

For children, take a limp with fever seriously and go the same day.

For anyone with a joint replacement and a painful joint, contact the surgical team.

For a diabetic foot ulcer, ask whether it probes to bone and ask for the multidisciplinary foot service urgently.

Do not accept a course of oral antibiotics as sufficient for bone or joint infection without specialist assessment.

Complete the full course, which will be long, and ask what the plan is for line care.

Ask for physiotherapy during and after treatment to preserve joint function.

Watch for return of pain, swelling or fever after treatment ends.

Where to get help

999 or A and E for a hot, swollen, painful joint.

The orthopaedic or infection team; the original surgical team for infected joint replacements.

A multidisciplinary diabetic foot service for foot ulcers reaching bone.

UK Sepsis Trust for the sepsis warning signs.