Review Question - QID 219866

A 45-year-old male presents with a vague, dull ache in the proximal forearm and episodes of tingling and numbness radiating into the thenar eminence, as well as the volar thumb, index, and middle fingers. The patient notes a lack of pain at night or early morning. On examination, you can recreate his pain by both continued compression as well as repeated tapping at the volar forearm, but not at the wrist. With their elbow extended, you ask the patient to flip their hand from a palm up to a palm down position, similarly increasing their pain. Neither resisted supination and elbow flexion, nor resisted finger flexion recreate his symptoms. The anatomic structure most likely implicated in this patient’s compressive neuropathy has which of the following attachment sites?