**Core Concept:** Anterior Cruciate Ligament (ACL) injury in a football player presenting with twisting injury, normal X-ray, but positive anterior drawer and Lachman tests.

**Why the Correct Answer is Right:**

In this scenario, the correct answer is **D**. ACL (Anterior Cruciate Ligament) is a crucial stabilizer of the knee joint, preventing excessive anterior translation of the tibia on the femur. When an athlete sustains a twisting injury, the forces acting on the knee joint can disrupt the ACL.

**Why Each Wrong Option is Incorrect:**

A. **Option A:** A normal X-ray does not rule out an ACL injury, as an X-ray is not sensitive enough to detect ligamentous injuries.

B. **Option B:** The presence of pain does not definitively diagnose an ACL injury, as pain is a common symptom in various musculoskeletal conditions.

C. **Option C:** A normal examination does not rule out an ACL injury; a positive clinical examination (anterior drawer and Lachman tests) suggests the injury.

**Why the Correct Answer is Right:**

Clinical examination plays a crucial role in diagnosing ACL injuries, particularly the anterior drawer and Lachman tests. Both tests assess the stability of the knee joint by applying specific forces, which in this case, are positive, indicating an ACL injury. ACL injuries are commonly associated with a positive result in these tests.

**Clinical Pearl:** ACL injuries can often be diagnosed using clinical examination tests, despite a normal X-ray. These tests serve as a valuable tool to guide the diagnosis, often facilitating a definitive diagnosis in the absence of an injury-specific radiological finding.