**Core Concept**
The ankle joint is a complex hinge-type synovial joint that can be prone to various ligamentous injuries due to its delicate balance of stability and mobility. The ligaments surrounding the ankle joint provide crucial support and stability to the joint, and injuries to these ligaments can lead to chronic instability and pain.

**Why the Correct Answer is Right**
The most common ligament injured around the ankle joint is the **Anterior Talofibular Ligament (ATFL)**. This ligament is responsible for providing stability to the anterior (front) part of the ankle joint, and it is often subjected to excessive stress and strain, particularly during inversion injuries. The ATFL is composed of dense collagen fibers that provide tensile strength to the ligament.

**Why Each Wrong Option is Incorrect**
* **Option A:** The Posterior Talofibular Ligament (PTFL) is also a crucial ligament surrounding the ankle joint, but it is less commonly injured compared to the ATFL.
* **Option B:** The Calcaneofibular Ligament (CFL) is another ligament that provides stability to the ankle joint, but it is not the most commonly injured ligament.
* **Option D:** The Deltoid Ligament is a strong ligament that provides medial (inner) stability to the ankle joint, but it is less commonly injured compared to the ATFL.

**Clinical Pearl / High-Yield Fact**
Inversion injuries of the ankle joint are the most common mechanism of injury leading to ATFL sprains, and early recognition and treatment of these injuries can prevent chronic ankle instability.

**Correct Answer:** A. Anterior Talofibular Ligament (ATFL).