A 37-year-old female physician presented with a chief complaint of left posterior thigh pain, which began insidiously approximately 4 months before her initial examination. Initially, she had been evaluated by her physician, and magnetic resonance imaging (MRI) was ordered. The MRI scan was reported to be within normal limits, with the exception of minimal disc bulging at L4-5. She had received physical therapy with little benefit and was referred for physiatric assessment. Review of the patient's original MRI scan showed the presence of perineurial (Tarlov) cysts within the sacral canal at the level of S2, with compression of the adjacent nerve root. Subsequent electrodiagnostic testing showed axonal degeneration consistent with an S1 radiculopathy. Tarlov cysts can be a rare cause of lumbosacral radiculopathy and should be considered in the differential diagnosis of radicular leg pain.