Septic arthritis
Septic, or infectious, arthritis is a medical emergency that occurs when bacterial invasion of a joint causes inflammation of the synovial lining, effusion and pyogenesis, and destruction of bone and cartilage. Septic arthritis can lead to ankylosis and even fatal septicemia. However, prompt antibiotic therapy and joint aspiration or drainage cures most patients.
Causes and incidence
In most cases of septic arthritis, bacteria spread from a primary site of infection — usually in adjacent bone or soft tissue — through the bloodstream to the joint. Common infecting organisms in children are group B Streptococcus and Haemophilus influenzae. Adults are usually infected by Staphylococcus, Streptococcus (pneumonia), and group B Streptococcus, whereas chronic septic arthritis is caused by Mycobacterium tuberculosis and Candida albicans.
Various factors can predispose a person to septic arthritis. Any concurrent bacterial infection (of the genitourinary or the upper respiratory tract, for example) or serious chronic illness (such as malignancy, renal failure, rheumatoid arthritis, systemic lupus erythematosus, diabetes, or cirrhosis) heightens susceptibility. Consequently, elderly people and those who abuse I.V. drugs run a higher risk of developing septic arthritis. Of course, diseases that depress the immune system and immunosuppressive therapy increase susceptibility. Other predisposing factors include recent articular trauma, joint arthroscopy or other surgery, intra-articular injections, and local joint abnormalities.
Septic arthritis may be seen at any age in children, but it occurs most often in children younger than age 3. It’s uncommon from age 3 until adolescence, at which time the incidence increases again.
Signs and symptoms
Acute septic arthritis begins abruptly, causing intense pain, inflammation, and swelling of the affected joint and low-grade fever. It usually affects a single joint. It most commonly develops in the large joints but can strike any joint, including the spine and small peripheral joints. The hip is a frequent site in infants. Systemic signs of inflammation may not appear in some patients. Migratory polyarthritis sometimes precedes localization of the infection. If the bacteria invade the hip, pain may occur in the groin, upper thigh, or buttock or may be referred to the knee.
Diagnosis
CONFIRMING DIAGNOSIS Identifying the causative organism in a Gram stain or culture of synovial fluid or a biopsy of synovial membrane confirms septic arthritis. When synovial fluid culture is negative, positive blood culture may confirm the diagnosis.
Joint fluid analysis shows gross pus or watery, cloudy fluid of decreased viscosity, usually with 50,000/µl or more white cells, primarily neutrophils. Synovial fluid glucose is usually more than 40 mg/dl. (See Other types of arthritis, page 584.)
Other diagnostic measures include the following:
❑ X-rays can show typical changes as early as 1 week after initial infection — distention of joint capsules, for example, followed by narrowing of joint space (indicating cartilage damage) and erosions of bone (joint destruction).
❑ White blood cell count may be elevated, with many polymorphonuclear cells; erythrocyte sedimentation rate is increased.
Treatment
Antibiotic therapy should begin as soon as a Gram stain has been done; it may be modified when drug sensitivity of the infecting organism is known. Bioassays or bactericidal assays of synovial fluid and bioassays of blood may confirm clearing of the infection.
Rest, immobilization, elevation, and warm compresses help with pain relief. Analgesics are given for pain, if needed. The affected joint can be immobilized with a splint or put into traction until the patient can tolerate movement.
In severe cases, needle aspiration (arthrocentesis) or surgery may be done under sterile conditions to remove grossly purulent or infected joint fluid. Late reconstructive surgery is warranted only for severe joint damage and only after all signs of active infection have disappeared, which usually takes several months. Recommended procedures include arthroplasty and joint fusion. Prosthetic replacement remains controversial because it may exacerbate the infection, but it has helped patients with damaged femoral heads or acetabula.
Special considerations
Management of septic arthritis demands meticulous supportive care, close observation, and control of infection.
❑ Practice strict sterile technique for all procedures. Wash hands carefully before and after giving care. Dispose of soiled linens and dressings properly. Prevent contact between immunosuppressed patients and infected patients.
❑ Watch for signs of joint inflammation: heat, redness, swelling, pain, or drainage. Monitor vital signs and fever pattern. Remember that corticosteroids mask signs of infection.
❑ Check splints or traction regularly. Keep the joint in proper alignment, but avoid prolonged immobilization. Start passive range-of-motion exercises immediately, and progress to active exercises as soon as the patient can move the affected joint and put weight on it.
❑ Monitor pain levels and medicate accordingly, especially before exercise, remembering that the pain of septic arthritis is easy to underestimate. Administer analgesics and opioids for acute pain and heat or ice packs for moderate pain.
ELDER TIP Prolonged use of opioids in an older adult necessitates particular vigilance because these drugs can impair mental status and may contribute to falls and other accidents.
❑ Warn the patient before the first aspiration that it will be extremely painful. Carefully evaluate the patient’s condition after joint aspiration.
Pictures
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
Other Book Chapters Related to Arthritis-like symptoms
Read excerpts from these other book chapters related to Arthritis-like symptoms:
Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2008 Williams & Wilkins.
More About Causes of Arthritis-like symptoms
» Next page: Acute Monoarticular Arthritis (Field Guide to Bedside Diagnosis)
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