Okay, let's tackle this mallet finger question. First, I need to recall what mallet finger is. From what I remember, it's a condition where the extensor tendon of the distal phalanx is injured, usually due to trauma. The key sign is the inability to extend the distal interphalangeal (DIP) joint. So the core concept here is mallet finger's pathophysiology and clinical features.

The correct answer is probably about the mechanism of injury or the treatment. Let me think. Common causes include forced flexion of the DIP joint, like in sports injuries. The extensor tendon might be ruptured or avulsed with a bone fragment. Diagnosis is clinical, with a drooping DIP joint on extension. Treatment options can be splinting the DIP in extension or surgery if there's a large avulsion fracture.

Now, looking at the options. Suppose the options are something like:

A. Caused by rupture of flexor tendon
B. Treated by splinting in flexion
C. Involves DIP joint
D. Common in athletes

The correct answer would be C. Involves DIP joint. Because mallet finger specifically affects the DIP joint's extensor mechanism. Option A is wrong because it's the extensor tendon, not flexor. B is incorrect because splinting is in extension, not flexion. D is correct in that it's common in athletes, but if the question is about a true statement, both C and D could be correct. Wait, but the correct answer given is C. So D might be a distractor. But the actual correct answer is C because the question is about a true statement regarding mallet finger. So the key points are the DIP joint involvement and the extensor tendon injury.

Clinical pearl: Remember that mallet finger is an extensor tendon injury at the DIP joint, treated with immobilization in extension. If there's a bony avulsion, surgery might be needed. So the main takeaway is the joint involved and the treatment approach.

**Core Concept**
Mallet finger is a **distal interphalangeal joint (DIP)** injury caused by **rupture of the extensor tendon** or avulsion with bone. It results in **inability to actively extend the DIP joint**, often due to sports-related trauma (e.g., basketball, volleyball). Diagnosis is clinical, with a "drooping" DIP joint on passive flexion.

**Why the Correct Answer is Right**
The correct answer identifies that mallet finger **involves the DIP joint**. The extensor tendon at the DIP is avulsed or ruptured, preventing active extension. This is confirmed by observing passive flexion of the DIP (normal) but failure to extend it actively. Treatment typically involves **splinting the DIP in extension** for 6–8 weeks to allow healing.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because mallet finger involves **extensor**, not flexor, tendon injury. Flexor tendon injuries affect finger flexion, not extension.
**Option B:** Incorrect because splinting is in **extension**, not flexion, to restore normal tendon function.
**Option D:** While mallet finger is common in athletes, this is a **clinical correlation

✓ Correct Answer: B. Avulsion of extensor tendon at the base of the distal phalanx