**Core Concept**
A fall onto the heel can lead to a fracture of the os calcis (calcaneus), a common type of intra-articular fracture in the foot. The os calcis is a critical weight-bearing bone that plays a significant role in ankle joint stability.

**Why the Correct Answer is Right**
The mechanism of injury in a fall onto the heel involves a compression force that causes a fracture of the os calcis. This type of fracture often results from an axial load on the foot, which can be seen in falls from a height or direct blows to the heel. The fracture typically occurs at the posterior-inferior aspect of the calcaneus, where the bone is thinnest. The fracture fragments can cause damage to the surrounding soft tissues, including the Achilles tendon and the posterior talofibular ligament.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not directly related to the mechanism of injury in a fall onto the heel.
**Option B:** While a fracture of the os calcis can be associated with other injuries, this option is not the most common association.
**Option C:** This option is not a direct consequence of a fall onto the heel.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient with a suspected fracture of the os calcis, it's essential to assess for associated injuries, including damage to the surrounding soft tissues and potential neurovascular compromise. A thorough physical examination and imaging studies, such as X-rays or CT scans, are necessary to confirm the diagnosis and guide treatment.

**Correct Answer: C. Peroneal tendon injury**