A 50 year oldlady sprained her ankle 2 months back from which she made a steady recovery. 2 months after the injury she gradually developed severe pain in her right ankle with significant limitation of ankle movement. Clinical examination reveals edema and shiny skin. What is the likely diagnosis ?

**Core Concept**
Post-traumatic ankle pain can be attributed to various complications, including osteoarthritis, complex regional pain syndrome (CRPS), or nerve injuries. However, the combination of severe pain, edema, shiny skin, and limited ankle movement points towards a specific diagnosis.

**Why the Correct Answer is Right**
The patient's symptoms, particularly the development of severe pain and limited ankle movement 2 months after the initial injury, are consistent with complex regional pain syndrome (CRPS). CRPS is characterized by chronic pain, edema, and skin changes in the affected limb following a traumatic injury. The exact pathophysiology of CRPS is not fully understood, but it is thought to involve sympathetic nervous system dysfunction, which leads to abnormal pain processing and inflammation.

**Why Each Wrong Option is Incorrect**
* **Option A:** Osteoarthritis typically presents with joint pain and stiffness, but not typically with the sudden onset of symptoms or the presence of edema and shiny skin.
* **Option B:** Nerve injuries can cause pain and weakness, but they do not typically result in the widespread symptoms seen in this patient, including edema and shiny skin.
* **Option C:** Other post-traumatic complications, such as infection or deep vein thrombosis, are less likely given the patient's steady recovery from the initial injury and the absence of systemic symptoms.

**Clinical Pearl / High-Yield Fact**
CRPS is often divided into two types: CRPS I (without nerve injury) and CRPS II (with nerve injury). The diagnosis of CRPS relies on clinical criteria, including the presence of chronic pain, edema, and skin changes in the affected limb, as well as the absence of other underlying conditions that could explain the symptoms.

**Correct Answer:** C. Complex regional pain syndrome (CRPS).

✓ Correct Answer: B. Complex Regional pain syndrome Type I (CRPS I)