**Core Concept**
The patient's presentation suggests a diagnosis related to the skeletal system, specifically involving abnormal growth and formation of bone. The costochondral junction and metaphysis are areas of bone growth, and the white line of Fraenkel is a radiographic sign associated with certain bone disorders.

**Why the Correct Answer is Right**
The patient's symptoms and radiographic signs are characteristic of rickets, a disease caused by vitamin D deficiency or phosphate deficiency. Rickets leads to softening and weakening of bones, resulting in deformities and growth abnormalities. The white line of Fraenkel is a radiographic sign seen in rickets, representing a zone of provisional calcification. The costochondral junction is also affected, causing enlargement and pain.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the patient's presentation. The symptoms and radiographic signs do not match a diagnosis of osteomalacia, which is a disease similar to rickets but occurs in adults.
**Option B:** This option is incorrect because it is not a valid diagnosis. The patient's symptoms and radiographic signs do not match a diagnosis of osteogenesis imperfecta, a genetic disorder of bone fragility.
**Option C:** This option is incorrect because it is not a valid diagnosis. The patient's symptoms and radiographic signs do not match a diagnosis of fibrous dysplasia, a benign bone disorder.

**Clinical Pearl / High-Yield Fact**
Rickets is a preventable disease, and its diagnosis is often delayed due to a lack of awareness about its symptoms and radiographic signs. Vitamin D deficiency is a common cause of rickets, and supplementation can prevent and treat the disease.

**Correct Answer:** A. Rickets