**Core Concept**
Posterior dislocation of the hip is a serious injury that occurs when the femoral head is displaced out of the acetabulum in a posterior direction. This type of dislocation often results from high-energy trauma, such as a motor vehicle accident or a fall from a height.

**Why the Correct Answer is Right**
In a posterior dislocation of the hip, the femoral head is typically displaced posteriorly, often in conjunction with external rotation of the affected limb. This displacement can lead to a characteristic "gunstock" deformity, where the affected leg appears shortened and externally rotated. The sciatic nerve, which runs along the posterior aspect of the thigh, may be compromised in this type of dislocation, leading to symptoms such as numbness, tingling, and weakness in the affected limb.

**Why Each Wrong Option is Incorrect**
**Option A:** Posterior dislocation of the hip is often associated with fractures of the femoral head or acetabulum, but this is not a defining characteristic of the injury.

**Option B:** The "gunstock" deformity is a classic sign of posterior dislocation of the hip, but this option is incomplete and does not accurately describe the typical presentation.

**Option C:** While the sciatic nerve may be compromised in posterior dislocation of the hip, this option is too vague and does not accurately describe the typical presentation of the injury.

**Clinical Pearl / High-Yield Fact**
To diagnose posterior dislocation of the hip, it's essential to perform a thorough physical examination, including assessment of the affected limb's length, rotation, and neurovascular status. A characteristic "gunstock" deformity, combined with a history of high-energy trauma, can help clinicians make a diagnosis.

**Correct Answer:** D