A 50-year-old male presented with back pain and numbness of the lower extremities persisting for 10 years. He had played volleyball for a long period until recently. He had no history of meningitis or traumatic injury. Magnetic resonance imaging revealed a syringomyelia located in the region from T8 to T9 without contrast enhancement or Chiari malformations. Computed tomography showed T9-10 spinal stenosis caused by the right enlarged ossified yellow ligament. Decompressive laminectomy was performed and the ossified ligament removed. Due to the finding of arachnoid thickening and adhesions during the intradural operation, shunting was also performed. Postoperatively, the neuroimaging and clinical findings improved. Syringomyelia is often associated with Chiari malformations, trauma, spinal tumor, hemorrhaging, and meningitis. We suggest that repeated minor mechanical damage caused by physical exercise in addition to long-standing compression of the spinal cord due to spinal spondylosis could induce severe arachnoid fibrotic change similar to adhesive arachnoiditis, which may be one of the main triggers of syringomyelia. Extradural decompressive surgery is considered to be the initial treatment for syringomyelia associated with spinal spondylosis.