Post-traumatic knee pain leading to the diagnosis of spondyloarthropathy

The authors report a patient with persistent left knee pain after traumatic injury. The initial bone scan seemed to confirm a valgus stress knee injury. The final diagnosis, however, was focal inflammation of the knee ligaments (enthesopathy) related to ankylosing spondylitis. The diagnostic procedure and the results of other imaging modalities are presented. The bone scan findings are discussed.