Rheumatoid arthritis (RA) is a debilitating inflammatory condition characterised by joint damage that affects the cervical spine most commonly at the atlantoaxial joint resulting in neck pain and myelopathy. The pathogenesis of RA involves the formation of a hyperplastic synovial tissue, termed pannus, which invades the local bone and causes osseous erosion. Here, we describe a case of rapid onset quadriparesis due to spinal cord compression at C5–C6 secondary to vertebral subluxation and mass effect from a large inflammatory pannus in the subaxial spine. Surgical decompression and resection of the subaxial pannus were performed, and the patient regained strength in all extremities. Histopathologic evaluation of the resected tissue confirmed the diagnosis of pannus over other more common epidural masses. Pannus formation commonly occurs in the peri-odontoid region; however, its presentation as a large soft tissue mass in the subaxial spine is not described in the current literature. Therefore, pannus should be considered in the differential diagnosis of epidural masses in the spine of RA patients. We use this case to discuss the pathology and radiological findings relevant to rheumatoid pannus formation in the subaxial cervical spine, as well as emphasise the importance of treatment in the context to severe degenerative disease.