Septic arthritis of a lumbar facet joint associated with epidural and paravertebral soft tissue abscess

Septic arthritis of the lumbar facet joint is rare, probably underdiagnosed, often associated with complications such as epidural abscess and paraspinal muscles abscess. Diagnosis is based on imaging evaluation. Plain radiographs of the lumbar spine are not helpful because often nomal. Bone scintigraphy is very sensitive but non-specific. CT scan can confirm the diagnosis and guide the needle biopsy. MRI is the preferred imaging modality for diagnosis. MRI shows early bone and joint involvement and it is helpful in detecting epidural and paravertebral soft tissue lesions.