Bone and joint infections
- Septic arthritis
- Gout
- Crystal-induced arthropathy characterized by periodic flares of severe joint pain, erythema, and effusion
- Appearance of the affected joint may be indistinguishable from a septic joint, and fever may be present
- Distinction is made by the presence in synovial fluid of negatively birefringent monosodium urate crystals (gout) or positively birefringent calcium pyrophosphate dihydrate crystals (pseudogout) on polarized light microscopy
- Trauma
- Traumatic injury to a joint is typically apparent from history or physical examination
- Erythema and warmth over the affected area are less likely to be present; however, the presentation of an acute fracture with hematoma may be similar
- In cases in which it is impossible to obtain a substantial history (eg, in patients with loss of consciousness, cerebrovascular accident, or cognitive or sensory deficit), differentiation is more reliant on laboratory investigations
- Differentiated by history, physical examination, and, if necessary, joint fluid analysis
- Gout
- Osteomyelitis
- Charcot arthropathy
- Progressive form of neuroarthropathy characterized by joint destruction and deformity in the foot (usually in patients with diabetic peripheral neuropathy) (Related: Diabetic peripheral neuropathy)
- Presents with localized erythema, warmth, and swelling of affected area; may also develop ulceration
- May be difficult to distinguish from osteomyelitis clinically and on imaging; bone biopsy may be required
- Malignancy
- Primary and metastatic bone tumors may present with bone pain, with or without localized swelling
- Primary bone tumors (eg, osteoid osteoma, osteosarcoma, chondrosarcoma, fibrosarcoma) may mimic osteomyelitis
- Lymphoma and multiple myeloma may also result in similar clinical manifestations (Related: Multiple myeloma)
- Unlike osteomyelitis, these conditions may be associated with abnormal calcium, phosphate, and alkaline phosphatase levels
- Diagnosed on basis of radiologic features and confirmed by biopsy
- Spinal epidural abscess
- Characterized by fever, back pain (usually excruciating and radicular), and neurologic deficits (eg, sensory and/or motor loss distal to the lesion, urinary retention)
- Typically associated with severe systemic illness characteristic of sepsis
- Diagnosed on basis of clinical and MRI or CT scan findings
- May be associated with vertebral osteomyelitis or diskitis
- Charcot arthropathy
