Synovial cyst in a posterior lumbar joint associated with sacralization at L5. Description of a case

Synovial cysts may occasionally be localized in the facet joints of the lumbar spine. These lesions are usually secondary to interapophyseal arthritis or trauma, that may cause hypermobility of the facet joints. Given the frequent association with arthrosis, synovial cysts are more often observed at L4-L5, which represents the level of greater mobility in the lumbar spine, in subjects aged over 50 years. A rare case of synovial cyst of the posterior joint of L5-S1 associated with sacralization of L5, a congenital anomaly that determines considerable segmental mechanical stability, is described.