Septic arthritis can lead to significant morbidity if not treated in a timely manner.
Because the history and physical examination has limitations, arthrocentesis should be performed in anyone suspected of having a septic arthritis.
A combination of the patient’s presentation, risk factors, and synovial fluid tests determine appropriate management decisions.
Emergency physicians’ greatest concern and diagnostic dilemma when faced with patients presenting with nontraumatic acute joint pain is septic arthritis. The invasion by bacteria and the associated immune response can lead to rapid joint destruction and irreversible loss of function. Yet, despite the severity of the condition, misconceptions about patient presentations and the evaluation of patients with possible septic joints persist in all aspects of health care.
Septic arthritis affects approximately 2–10 people per 100,000 annually and is frequently encountered in the emergency department (ED) setting. Once infected, the joint cartilage is rapidly injured, with up to 30% of patients experiencing residual damage and up to 10% dying as a result of the septic joint. Septic arthritis typically affects young children and adults older than 55 years; however, any age group can be affected. The microbiology of septic joints can be divided into 2 groups: nongonococcal and gonococcal. Nongonococcal pathogens include Staphylococcus aureus (50%), Streptococcus pneumoniae, Streptococcus pyogenes (25%), and gram-negative bacilli (20%). Hematogenous spread is more common than contiguous extension from a local cellulitis or penetrating injury. Although the incidence of gonococcal arthritis has declined over the past 2 decades, it is the leading cause of septic arthritis among sexually active individuals and causes 5% of all septic joints.
Patients typically develop symptoms over the span of hours to days. Symptoms present in more than half of patients with septic arthritis include joint pain, joint swelling, and fever. Sweats and rigors are less common findings. Patients will typically splint the joint and resist any active or passive range of motion. If patients have a history of similar episodes, the likelihood of septic arthritis decreases and the likelihood of other forms of arthritis increase. Although typically monoarticular and affecting the knee, polyarticular involvement occurs in 10% of cases. Risk factors for septic arthritis include immunosuppression (eg, diabetes), injection drug use, elderly, prosthetic joint, and previous joint injury (eg, rheumatoid arthritis).
Gonococcal septic arthritis typically has a slightly different presentation. A prodromal phase with migratory arthritis and tenosynovitis is the major feature before one or more joints become involved. Patients may describe features of gonococcal disease such as vaginal discharge, pelvic pain, penile discharge, or pustules on the hands.
Although patients can appear toxic, most patients will not have vital sign abnormalities, including fever. The goal of the examination is to attempt to distinguish a joint infection from inflammation or infection of the surrounding structures (bursa, tendons, skin). A septic joint typically has diffuse swelling, redness, and warmth. Pain severely limits both active and passive range of motion. This is in contradistinction to inflammation or infection of surrounding structures, in which pain is more severe with active range of motion.
Gonococcal arthritis may have more subtle signs. It commonly affects the wrist, knee, and/or ankle and is associated with tenosynovitis, rash, and migratory arthritis. Immunocompromised patients and those with prosthetic joints also have more subtle exam findings. In these patients, less of an immune response is generated with invasion of the joint. Therefore, the classic teaching of a red, hot, swollen, painful joint does not always predict septic arthritis.
