**Core Concept:** Gritty pain in the eye and joint pain can be associated with a systemic condition called Reactive Arthritis (ReA), also known as Post-infectious Arthritis. ReA is a type of inflammatory arthritis that occurs following a gastrointestinal or genitourinary infection.

**Why the Correct Answer is Right:** Reactive arthritis results from a post-infectious autoimmune response. It typically follows a gastrointestinal or genitourinary infection, such as those caused by Chlamydia, Salmonella, or Shigella bacteria. The immune system misinterprets bacterial antigens as self-antigens, leading to inflammation in joints, eyes, and other organs. In this case, the patient's symptoms match the clinical picture of Reactive Arthritis.

**Why Each Wrong Option is Incorrect:**

A. **Gout:** Gout is another inflammatory arthritis that primarily affects joints, but it is not associated with eye pain, and has different triggers (elevated uric acid levels).

B. **Rheumatoid Arthritis:** Rheumatoid Arthritis is an autoimmune disorder affecting joints symmetrically, whereas Reactive Arthritis typically involves joints asymmetrically and may have a preceding infection.

C. **Osteoarthritis:** Osteoarthritis is a degenerative joint disease, not post-infectious and does not involve the eye.

D. **Neurogenic Arthritis:** Neurogenic arthritis is caused by a nerve injury, not a preceding infection, and typically affects weight-bearing joints, not typically the eye.

**Clinical Pearl:** Reactive Arthritis is a rare but important differential diagnosis to consider in patients with recent gastrointestinal or genitourinary infections presenting with joint and eye pain. Timely diagnosis and treatment can prevent complications and improve the patient's outcome.