A 21-year-old javelin thrower is diagnosed with a full-thickness ulnar collateral ligament (UCL) tear. On presentation, he complains of numbness and tingling in the ring and small fingers. Which muscle group would he be most likely to have motor weakness

**Core Concept**
The ulnar collateral ligament (UCL) tear is a common injury in athletes, particularly those involved in throwing sports. The UCL is a critical stabilizer of the medial elbow, and its injury can lead to medial elbow instability. The **ulnar nerve**, which runs close to the UCL, can be affected by this injury, resulting in neurological symptoms.

**Why the Correct Answer is Right**
The **ulnar nerve** is responsible for innervating the muscles of the forearm and hand, particularly the **hypothenar muscles** and the **interosseous muscles**. Damage to the ulnar nerve can result in motor weakness of these muscle groups. The ulnar nerve also provides sensory innervation to the ring and small fingers, which explains the patient's symptoms of numbness and tingling.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the muscle group is not primarily innervated by the ulnar nerve.
**Option B:** This option is incorrect because, although the muscle is innervated by the ulnar nerve, it is not the most likely to be affected by a UCL tear.
**Option D:** This option is incorrect because the muscle group is not typically associated with ulnar nerve damage.

**Why Each Wrong Option is Incorrect (Continued)**
**Option C:** is the correct answer choice, so we will address the other options.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the ulnar nerve is closely associated with the UCL, and injuries to the UCL can result in ulnar nerve damage, leading to motor weakness and sensory symptoms in the hand.

**Correct Answer:** C. Hypothenar muscles and interosseous muscles

✓ Correct Answer: C. Abductor digiti minimi