From the Guidelines
Septic arthritis cannot be ruled out solely based on the absence of pain on passive range of motion, as this finding is not universal and can be influenced by various factors such as early stages, immunocompromised states, or pain medications. While pain with passive movement is a classic feature of septic arthritis due to joint inflammation and increased intra-articular pressure, some patients may not exhibit this sign. According to the American College of Radiology Appropriateness Criteria for osteomyelitis or septic arthritis in children, excluding axial skeleton 1, septic arthritis is considered an orthopedic emergency because bacterial proliferation and metabolites can rapidly result in cartilage damage. The diagnosis of septic arthritis is made by arthrocentesis, and clinical suspicion should remain high even without pain on passive motion if other concerning features are present, such as joint swelling, warmth, erythema, fever, and limited active range of motion.
Key considerations in the diagnosis of septic arthritis include:
- Joint aspiration with synovial fluid analysis for cell count, Gram stain, and culture, as supported by the American College of Radiology Appropriateness Criteria for suspected osteomyelitis, septic arthritis, or soft tissue infection 1
- Laboratory findings such as elevated white blood cell count, C-reactive protein, and erythrocyte sedimentation rate, which can support the diagnosis
- Imaging studies, such as image-guided joint aspiration, which can be used to evaluate suspected septic arthritis and confirm intra-articular needle positioning.
Given the serious consequences of missed septic arthritis, including joint destruction and sepsis, a thorough clinical evaluation combined with appropriate laboratory and imaging studies is essential for accurate diagnosis. The absence of pain on passive range of motion should not be used as a sole criterion to rule out septic arthritis, and a high index of suspicion should be maintained in patients with other concerning features.
From the Research
Septic Arthritis and Pain on Passive Range of Motion
- The provided studies do not directly address the relationship between septic arthritis and pain on passive range of motion 2, 3, 4, 5, 6.
- However, it is known that septic arthritis is characterized by acute onset of monoarticular inflammation of a joint due to an infectious etiology, which can cause significant pain and discomfort 2.
- The clinical presentation of septic arthritis can overlap with those of many other joint conditions, making diagnosis challenging 2.
- While pain on passive range of motion may be a symptom of septic arthritis, it is not a definitive diagnostic criterion 5.
- A diagnosis of septic arthritis typically requires the direct demonstration of bacteria in synovial fluid or on positive culture of the pathogen, as well as other diagnostic tests such as synovial fluid studies and serum markers 4, 5.
Ruling Out Septic Arthritis
- The absence of pain on passive range of motion does not necessarily rule out septic arthritis, as the condition can present with varying degrees of pain and stiffness 3, 4.
- A thorough diagnostic evaluation, including synovial fluid analysis and adjunctive lab tests, is necessary to confirm or rule out septic arthritis 6.
- The provided studies emphasize the importance of prompt diagnosis and treatment of septic arthritis to avoid permanent morbidity and mortality 2, 3, 4, 5.