**Core Concept**
The postero lateral anconeus triangle is an anatomical region in the elbow, characterized by a specific arrangement of bones and muscles. It is an important landmark for surgeons and medical professionals to identify during various procedures. This triangle is bounded by the olecranon, the lateral epicondyle of the humerus, and the posterior border of the ulna.

**Why the Correct Answer is Right**
The postero lateral anconeus triangle is formed by the intersection of the olecranon, the lateral epicondyle of the humerus, and the posterior border of the ulna. This specific arrangement of bones creates a unique triangular region that is clinically significant. The anconeus muscle, which is located within this triangle, plays a crucial role in elbow extension.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the olecranon is a key landmark in the formation of the postero lateral anconeus triangle, but it is not the only structure involved.
**Option B:** This option is incorrect because the lateral epicondyle of the humerus is a crucial component of the triangle, but it is not the only structure involved.
**Option C:** This option is incorrect because the posterior border of the ulna is a key landmark in the formation of the postero lateral anconeus triangle, but it is not the only structure involved.

**Clinical Pearl / High-Yield Fact**
The anconeus muscle, located within the postero lateral anconeus triangle, is often overlooked during surgical procedures. However, it plays a crucial role in elbow extension and should be identified and preserved during surgical interventions.

**Correct Answer:** C. The posterior border of the ulna, the olecranon, and the lateral epicondyle of the humerus form the postero lateral anconeus triangle.