**Core Concept**
The extensor pollicis longus (EPL) tendon is a vital structure for thumb extension. It arises from the posterior surface of the ulna and inserts into the base of the distal phalanx of the thumb. EPL tendon rupture can lead to significant impairment of thumb function, causing difficulties in daily activities.

**Why the Correct Answer is Right**
EPL tendon rupture is a known complication of scaphoid fractures. The mechanism involves the scaphoid tubercle, where the EPL tendon inserts. When the scaphoid is fractured, the EPL tendon can be avulsed from its insertion site, leading to rupture. This is often seen in patients with scaphoid fractures that are not properly immobilized or treated.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because EPL tendon rupture is not a common complication of De Quervain's tenosynovitis. De Quervain's tenosynovitis affects the first dorsal compartment of the wrist, which contains the tendons of the abductor pollicis longus and extensor pollicis brevis.

**Option B:** This option is incorrect because EPL tendon rupture is not typically associated with rheumatoid arthritis. While rheumatoid arthritis can cause tendon inflammation and damage, it is more commonly associated with other tendon ruptures, such as the Achilles tendon.

**Option C:** This option is incorrect because EPL tendon rupture is not a common complication of osteoarthritis. Osteoarthritis can cause joint damage and inflammation, but it is not typically associated with EPL tendon rupture.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that EPL tendon rupture can occur even in the absence of a clear traumatic event. Patients with scaphoid fractures or other wrist injuries should be carefully evaluated for EPL tendon rupture, even if they do not report a specific mechanism of injury.

**Correct Answer:** D