**Core Concept**
The median nerve innervates several muscles in the forearm, including the flexor digitorum profundus (lateral half), flexor digitorum superficialis, flexor pollicis longus, pronator quadratus, and thenar muscles (opponens pollicis, flexor pollicis brevis, and abductor pollicis brevis). However, the median nerve does not innervate all these muscles, and there is a specific muscle that is spared in median nerve injury at the elbow.

**Why the Correct Answer is Right**
The median nerve injury at the elbow affects the muscles innervated by the anterior interosseous branch of the median nerve, which includes the flexor digitorum profundus (lateral half), flexor pollicis longus, and pronator quadratus. However, the flexor carpi radialis is a muscle that is innervated by the median nerve but is spared in median nerve injury at the elbow. This is because the flexor carpi radialis receives its nerve supply from the lateral anterbrachial cutaneous nerve, which is not affected by the median nerve injury.

**Why Each Wrong Option is Incorrect**
* **Option A:** The flexor digitorum profundus (lateral half) is innervated by the anterior interosseous branch of the median nerve and will be affected in median nerve injury at the elbow.
* **Option B:** The flexor pollicis longus is also innervated by the anterior interosseous branch of the median nerve and will be affected in median nerve injury at the elbow.
* **Option C:** The pronator quadratus is innervated by the anterior interosseous branch of the median nerve and will be affected in median nerve injury at the elbow.

**Clinical Pearl / High-Yield Fact**
The flexor carpi radialis is often spared in median nerve injury at the elbow because it receives its nerve supply from the lateral anterbrachial cutaneous nerve, which is not affected by the median nerve injury.

**Correct Answer:** C.