Background and Objectives The study was designed to investigate the patterns of referral pain associated with the thoracic zygapophyseal joints (C7-T1 to T2-3, T11-12).

Methods In 15 patients who had back pain suspected to be of zygapophyseal origin and for whom pain was relieved by injection of local anesthetic into the joints under fluoroscopic guidance, the zygapophyseal joints from C7-T1 to T2-3, T11-12 were distended by injecting contrast medium. If injection reproduced typical pain in the patient, the patient was asked to describe the distribution of pain, which was recorded on a body diagram.

Results A total of 21 joints were studied. Composite pain distribution maps for the thoracic zygapophyseal joints from C7-T1 to T2-3 and for the T11-12 joint were drawn. The distribution of referred pain was as follows: pain in the suprascapular region was referred from C7-T1 and Th1-2; pain in the superior angle of the scapula from C7-T1 and T1-2; pain in the midscapular region from C7-T1, T1-2, and Th2-3; and pain in the paravertebral region around the site of injection and the area over the iliac crest from T11-12.

Conclusions The referred pain distribution for joints C7-T1 to Th2-3 showed significant overlap.