1b.

A 47-year-old woman was referred to physical therapy with a diagnosis of lumbar radiculopathy. Weight-bearing flexion/extension radiographs showed no change in a 13-mm (at L5-S1) spondylolisthesis measured with a neutral posture. Physical therapy with a focus on flexion-biased stabilization exercises was initiated. After failing to improve after 6 weeks, her referring physician ordered magnetic resonance imaging, which revealed a 6-mm spondylolisthesis in a supine position. Additionally, the physical therapist performed an anterior stability test of L5 on S1 under C-arm fluoroscopy, which demonstrated a palpable shift of S1 posteriorly that was measured on imaging as a change from a 13-mm to a 17-mm spondylolisthesis. J Orthop Sports Phys Ther 2016;46(9):810. doi:10.2519/jospt.2016.0415.