Okay, let's tackle this question about cubitus valgus. The question is asking when cubitus valgus is seen. First, I need to recall what cubitus valgus means. Cubitus refers to the elbow, and valgus is a term for a deformity where the angle is increased, like in a knock-knee. So cubitus valgus would be when the elbow is bent outward more than normal.

The core concept here is the elbow anatomy and common deformities. Cubitus valgus is also known as "gunstock deformity," right? It's when the arm is held in a position where the forearm is angled outward, creating a larger than normal angle at the elbow. This is different from cubitus varus, which is a "waiter's tip" deformity where the elbow is bent inward.

Now, the correct answer is a condition that leads to this deformity. Common causes include malunion of a fracture, especially the medial epicondyle of the humerus. When that part of the bone heals in a way that shortens the medial side, it pulls the elbow into valgus. Also, congenital conditions like congenital cubitus valgus can be a cause. Another possibility is rheumatoid arthritis, which can cause ligamentous laxity leading to valgus deformity.

Looking at the options, even though they aren't listed, the correct answer would be the one that refers to a medial epicondyle fracture or its malunion. Let's say the options are A: Lateral epicondyle fracture, B: Medial epicondyle fracture, C: Olecranon fracture, D: Supracondylar fracture. Then B is correct because medial epicondyle fractures, if they heal improperly, lead to cubitus valgus.

The distractors: A is a lateral fracture, which would more likely cause varus if malunited. C and D might cause other deformities. For example, a supracondylar fracture could lead to cubitus varus if the medial part is retracted. Olecranon fractures might affect extension but not the valgus angle.

Clinical pearl: Remember that cubitus valgus is associated with medial epicondyle fractures, while cubitus varus is from lateral or medial epicondyle fractures with different healing. Also, check for ulnar nerve involvement in valgus deformities because of the stretched medial aspect.

**Core Concept**
Cubitus valgus is an elbow deformity characterized by increased valgus angle (>10°) due to medial shortening or lateral overgrowth. It commonly results from **malunion of medial epicondyle fractures** in children, leading to a "gunstock deformity" where the forearm appears angled outward relative to the upper arm.

**Why the Correct Answer is Right**
The correct answer is **medial epicondyle fracture malunion**. During healing, the medial epicondyle (a bony prominence on the inner elbow) fuses in a shortened position, reducing the medial column’s length. This causes the lateral side to overgrow, increasing the valgus angle. The deformity is most common in pediatric populations due to the prevalence of epiphyseal fractures at this site.

**Why Each Wrong Option is Incorrect**
**Option A:

✓ Correct Answer: A. Lateral condyle of humerus