**Core Concept**
The ischial tuberosity is a bony prominence located on the posterior aspect of the pelvis, serving as an attachment site for various muscles, tendons, and ligaments. The correct identification of structures attached to the ischial tuberosity is crucial for understanding pelvic anatomy and its clinical implications.

**Why the Correct Answer is Right**
The ischial tuberosity serves as an attachment site for the **Biceps femoris** (long head), **Semitendinosus**, and **Semitendinosus tendon**, **Gastrocnemius**, and **Piriformis** muscles. These muscles play a vital role in hip and knee joint movements, as well as pelvic stability. The ischial tuberosity also serves as an attachment site for the **Iliotibial tract** and **Thigh**.

**Why Each Wrong Option is Incorrect**
* **Option A:** The **Pectineus** muscle is actually attached to the **Pectineal line** of the pubic bone, not the ischial tuberosity.
* **Option B:** The **Adductor magnus** muscle has two parts: the **Adductor part**, which is attached to the **Linea aspera** of the femur, and the **Hamstring part**, which is attached to the ischial tuberosity. Therefore, it is partially attached to the ischial tuberosity.
* **Option C:** The **Tensor fasciae latae** muscle is attached to the **Anterior superior iliac spine** and the **Iliotibial tract**, not the ischial tuberosity.
* **Option D:** The **Piriformis** muscle is actually attached to the ischial tuberosity, making this option incorrect.

**Clinical Pearl / High-Yield Fact**
The ischial tuberosity is a common site for pressure sores and bursitis, particularly in individuals with prolonged sitting or weight-bearing activities. Awareness of the structures attached to the ischial tuberosity is essential for diagnosing and managing these conditions.

**Correct Answer:** D.