Lumbar facet synovial cyst.

orthopaedic clinic with low back pain and left leg pain for last three months. The low back pain was of gradual onset and was progressive. The pain was aggravated on walking and standing. On clinical examination the patient was fit and well. She had bilateral free straight leg raise. Femoral nerve stretch test on the left leg was positive. She was intact neurologically and the range of movements in the spine were terminally restricted. Both hips and sacral iliac joints were clinically normal. A clinical diagnosis of lateral canal stenosis was made. Magnetic resonance imaging (MRI) of the lumbosacral spine revealed a well defined posterolateral extradural cystic mass (see fig 1). It had a low intensity wall signal and a high intensity content signal. Associated degenerative and spondylolisthetic spine was noted. The cyst was in continuity with the degenerative facet and gadolinium enhancement of the cyst showed a lumbar facet synovial cyst.