A physician asks a patient to hold her right upper arm close to her lateral chest wall, and bend the arm at the elbow so that the palm is facing upward. The physician then directs the patient to turn her hand so that the palm faces downward, without bending her wrist. This maneuver causes discomfo to the patient, which the physician notes as pain on ?

**Core Concept**
The physician is performing a maneuver to assess the patient's radial nerve function, specifically the radial tunnel syndrome. The radial nerve is responsible for innervating the extensor muscles of the forearm and wrist, and its compression can cause pain and discomfort in the posterior aspect of the forearm and wrist.

**Why the Correct Answer is Right**
When the patient turns her hand so that the palm faces downward without bending her wrist, the radial nerve is stretched and compressed within the radial tunnel, leading to pain and discomfort. This is due to the anatomical arrangement of the radial nerve and its proximity to the radial head and the annular ligament, which can cause compression and irritation of the nerve. The radial nerve is responsible for innervating the extensor muscles of the forearm and wrist, and its dysfunction can lead to weakness and wasting of these muscles.

**Why Each Wrong Option is Incorrect**

* **Option A:** This option is incorrect because the maneuver described does not specifically target the median nerve, which is responsible for innervating the flexor muscles of the forearm and wrist. The median nerve is more commonly affected by compression at the carpal tunnel.
* **Option B:** This option is incorrect because the ulnar nerve is responsible for innervating the intrinsic muscles of the hand, including the interossei and the lumbricals. The ulnar nerve is more commonly affected by compression at the elbow or at the wrist.
* **Option C:** This option is incorrect because the axillary nerve is responsible for innervating the deltoid and the teres minor muscles, and is more commonly affected by compression at the shoulder joint.

**Clinical Pearl / High-Yield Fact**
The radial tunnel syndrome is a common cause of pain and discomfort in the posterior aspect of the forearm and wrist, and can be caused by compression of the radial nerve within the radial tunnel. It is often associated with activities that involve repetitive extension of the wrist and forearm, such as tennis or golf.

**Correct Answer: D.**

✓ Correct Answer: D. Pronation of the forearm