**Core Concept**
In orthopedics, a fracture is a break in the continuity of a bone. The clinical diagnosis of a fracture relies on a combination of physical examination, radiographic findings, and patient history. The key to diagnosing a fracture lies in identifying specific signs and symptoms that indicate a potential break in the bone.

**Why the Correct Answer is Right**
The correct options, **Abnormal mobility (A)**, **Crepitus (B)**, and **Failure to transmit movement proximally (C)**, are all indicative of a fracture. Abnormal mobility refers to the presence of excessive movement at the fracture site, which can be palpated or observed during physical examination. Crepitus, also known as a "grating" or "crunching" sensation, occurs when bone fragments rub against each other, producing a characteristic sound. Failure to transmit movement proximally indicates that the bone is no longer continuous, resulting in an abnormal transmission of movement.

**Why Each Wrong Option is Incorrect**
* **Option A:** While abnormal mobility is indeed a sign of fracture, it is not the only possible cause. Other conditions, such as joint effusion or ligament sprain, can also result in abnormal mobility.
* **Option B:** Crepitus can be present in other conditions, such as osteoarthritis or joint effusion, which are not necessarily related to fractures.
* **Option C:** Failure to transmit movement proximally can be seen in other conditions, such as ligament sprains or joint dislocations, which do not necessarily involve a fracture.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient for a potential fracture, it is essential to consider the mechanism of injury, the patient's history, and the physical examination findings. The Ottawa Knee Rule and the Canadian C-Spine Rule are two clinical decision tools that can help guide the diagnosis and management of fractures in the emergency department.

**✓ Correct Answer: D. All of above**