eMedicine Specialties > Orthopedic Surgery > Systemic Diseases

Septic Arthritis

Author: Gabriel Munoz, MD, Consulting Staff, Department of Emergency Medicine, Decatur Memorial Hospital
Coauthor(s): Edmund W Raycraft, MD, Consulting Staff, Raycraft & Jones Orthopedics
Contributor Information and Disclosures

Updated: Jul 14, 2009

Introduction

Septic arthritis is inflammation of a synovial membrane with purulent effusion into the joint capsule, usually due to bacterial infection. This disease entity also is referred to in the literature as bacterial, suppurative, purulent, or infectious arthritis.^1,2,3,4,5

Septic arthritis is a rather rare but important disease that typically affects monoarticular joints. The age range of those affected is broad, from the neonatal period to advanced age.^6,7,8,9,10 Treatment consists of a combined medical and surgical approach.^1,11,12,13 Septic arthritis usually is divided into gonococcal and nongonococcal arthritis, as clinical and treatment regimens differ.¹⁴ In adults, septic arthritis most commonly affects the knee; in children, infection into the hip joint predominates.^8,15,16,17

Despite advances in diagnostic studies, powerful antibiotics, and early drainage, significant joint destruction commonly occurs.

Recent studies

A retrospective comparison by Sammer and Shin of 36 patients (40 wrists) with septic arthritis of the wrist treated between 1997 and 2007 with either open or arthroscopic irrigation and debridement showed that arthroscopic irrigation and debridement is an effective treatment for patients with isolated septic arthritis of the wrist. Patients treated arthroscopically had fewer operations and a shorter hospital stay than patients who received open treatment; however, these benefits were not seen in patients with multiple sites of infection. The 90-day perioperative mortality rate was 18% (3 patients) in the open-treatment group and 21% (4 patients) in the arthroscopy group.¹⁸

Collins et al found that synovial fluid TREM-1 (triggering receptor expressed on myeloid cells-1) expression is increased in septic arthritis and rheumatoid arthritis. According to the authors, in patients with acute inflammatory arthritis, elevated synovial fluid sTREM 1 levels may help point to a diagnosis of septic arthritis or rheumatoid arthritis, and in patients with rheumatoid arthritis, targeting TREM-1 may provide therapeutic benefit by reducing local proinflammatory cytokine and chemokine release.¹⁹

Pessler et al, in an analysis of the synovium in patients with chronic pyogenic arthritis, identified extensive neovascularization and cell proliferation, persistent bacterial colonization, and heterogeneous inflammatory infiltrates rich in CD15+ neutrophils.²⁰

Problem

Septic arthritis can quickly destroy a joint and can cause many complications, including osteomyelitis, bony erosions, fibrous ankylosis, sepsis, and even death.

Barriers to successful management include lack of clinical suspicion in the early phase of presentation, delay in definitive diagnostic needle aspiration, and failure to provide adequate drainage of the joint.

In addition, septic arthritis in neonates and infants can be especially treacherous as a result of blunted inflammatory signals and/or confounding infection at a distant site (eg, ear, umbilical catheter site).

Frequency

Of all the forms of arthritis, septic arthritis is the most aggressive at quickly destroying a joint. The frequency of septic arthritis is approximately 2-10 cases per 100,000 in the general population.

In patients with immunologic disorders (eg, rheumatoid arthritis, systemic lupus erythematosus), the occurrence is approximately 30-70 cases per 100,000.²¹ The incidence in patients with joint prosthesis is similar to that of patients with immunologic disorders.

In gonococcal arthritis, women are approximately 3 times as likely as men to develop this disease.

Etiology

Most septic arthritis cases are caused by Staphylococcus aureus and streptococci. In all age groups, 80% of cases are caused by Gram-positive aerobes (60% S aureus; 15% beta-hemolytic streptococci; 5% Streptococcus pneumoniae), and approximately 20% of cases are caused by Gram-negative anaerobes.²²

In neonates and infants younger than 6 months, S aureus and Gram-negative anaerobes comprise the majority of infections. The incidence of Haemophilus influenzae has decreased dramatically owing to widespread use of the H influenzae vaccine.

In children aged 6 months to 2 years, S aureus and, to a lesser degree, H influenzae are the major organisms of infection. In patients older than 2 years, S aureus becomes the principle culprit. As sexual activity begins in the teen years, Neisseria gonorrhoeae should be suspected.

Pathophysiology

Various sources of infection exist for the joint space. Bacteria may enter the joint directly, as with trauma. Infection may enter hematogenously (eg, intravenous [IV] drug injection). Infection may enter from osteomyelitis that is adjacent to the capsule. Infection also may enter from soft-tissue infections (eg, cellulitis, abscess, bursitis, tenosynovitis). The knee accounts for approximately 40-50% of joint infections, and the hip accounts for 20-25% of joint infections. However, in infants and very young children, hip involvement is most common. Shoulders, ankles, and elbows account for approximately 10-15% of infections. Finally, septic arthritis of the wrist occurs in 10% of cases.^4,8,15,23,24

Presentation

Septic arthritis can be difficult to diagnose in the early stages of progression. Once purulence has developed and a bulging effusion is noted, diagnosis is made easily. Typically, the patient presents with fever and a joint that is hot, red, painful, distended, and has a markedly decreased range of motion. Restriction of movement occurs to active and passive attempts.^7,8,25,26,27

In young, sexually active patients with fever, tenosynovitis, migratory polyarthralgia, and dermatitis, suspect N gonorrhoeae. The rash may appear as papules over the trunk and extensor surfaces of distal extremities that eventually can turn into hemorrhagic pustules. Women are more likely to develop gonococcal arthritis than are men.

In patients with a history of intravenous drug use (IVDU), suspect Pseudomonas.

In infants and children, diagnosis can be very difficult. Neonates and infants often have blunted inflammatory signals. Symptoms such as fever, decreased appetite, and irritability without obvious joint involvement can easily lead to an incorrect diagnosis. Aside from obvious open fractures, foreign object, and trauma, searching for distant infections is very important. Clinical presentation in the older child will be similar to that in the adult. However, the child may not allow the affected joint to be touched and, sometimes, may not even allow the affected joint to be seen. Additional confounding symptoms may be present, including nausea, vomiting, headache, sore throat, and abdominal pain. Ear infections are the most common source of bacteria leading to septic arthritis in children.

Distinguishing transient synovitis from septic arthritis is an area of particular concern.²⁸ In 1 study of children, 4 independent variables have been found useful as clinical predictors for septic arthritis, including the following:

• History of fever
• Nonweightbearing
• Erythrocyte sedimentation rate higher than 40 mm/h
• WBC count higher than 12,000/µL

Indications

If rapid improvement is not achieved with needle aspiration, open drainage and lavage (arthroscopically or via arthrotomy) is strongly recommended.

Contraindications

Generally, few contraindications to arthrocentesis exist. One caveat to consider is to avoid aspirating from an area that has an established overlying soft-tissue infection. This may introduce bacteria into an otherwise noninfected joint.

Patients with bleeding disorders and those who are on anticoagulatory medications pose a difficult challenge, and risks must be weighed against benefits on an individual basis.

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