## Core Concept
Klippel-Feil syndrome is a rare congenital condition characterized by the abnormal fusion of any two of the seven cervical vertebrae. This condition often presents with a classic triad of symptoms. Understanding the clinical features of Klippel-Feil syndrome is essential for diagnosing and managing patients with this condition.

## Why the Correct Answer is Right
The characteristic triad of Klippel-Feil syndrome consists of:
- **Short neck**: Due to the fusion of cervical vertebrae, patients often have a visibly short neck.
- **Low posterior hairline**: The abnormal fusion and skeletal changes can lead to a lower-than-normal posterior hairline.
- **Limited neck mobility**: Fusion of the cervical vertebrae restricts movement of the neck.

## Why Each Wrong Option is Incorrect
- **Option A: Short neck** - This is a part of the classic triad.
- **Option B: Low posterior hairline** - Also a component of the classic triad.
- **Option C: Limited neck mobility** - This is the third component of the classic triad.
- **Option D: Webbed neck** - While webbed neck can be associated with various congenital anomalies, it is not a characteristic part of the classic triad of Klippel-Feil syndrome.

## Clinical Pearl / High-Yield Fact
A key clinical pearl for Klippel-Feil syndrome is that patients are at an increased risk for other congenital anomalies, including renal and cardiac abnormalities. Screening for these conditions is often recommended.

## Correct Answer: D. Webbed neck