Septic arthritis of the lumbar facet joint. Case and literature review

•Septic arthritis of facet joints is very rare.•Most cases are associated with raised inflammatory markers.•Normal inflammatory markers should not be used as a criterion of exclusion.•Radiological investigation should be performed in all suspected cases. Septic Arthritis of the facet joint (SAFJ) is an uncommon but severe condition of the spine with only 61 cases published to date. Diagnosis is notoriously difficult and can take several months which can lead to significant delays in treatment. We report a case of a 52-year-old female with 2-month history of back pain diagnosed with septic arthritis of the left lumbar L4/5 facet joint and associated epidural abscess. She presented with no fevers, normal neurological examination and normal blood parameters posing a diagnostic challenge. In this report we conclude normal inflammatory markers cannot be used as exclusion criteria for the disease. We also review the body of literature to summarise the key features of the condition to assist clinicians in its diagnosis.