Review Question - QID 218840

You are asked to evaluate a 32-year-old male in your office who is complaining of right forearm pain. He is a tennis pro at the nearby country club and has noticed the pain increasing for the last several months. On examination, you are able to elicit tenderness several centimeters proximal to the wrist joint over the dorsum of the forearm which is worse with resisted wrist and thumb extension. The patient occasionally complains of a popping sensation with these motions. He has tried bracing and undergone physical therapy without much benefit to this point. You recommend operative release of the likely causative structure. What is the bony insertion of the muscle/tendon which will effectively be decompressed by this release?