**Core Concept**
Kanavel's sign is a clinical diagnostic criterion used to identify the presence of suppurative tenosynovitis, particularly in the flexor tendons of the fingers. This condition is characterized by inflammation of the tendon sheath, often due to infection or trauma. The clinical manifestations of Kanavel's sign are a result of the body's inflammatory response to the injury.

**Why the Correct Answer is Right**
Kanavel's sign is diagnosed based on the presence of four cardinal signs: 1) pain on passive extension of the finger, 2) tenderness over the affected tendon, 3) fusiform swelling of the affected finger, and 4) a characteristic sausage-shaped swelling of the tendon. These signs are indicative of the inflammatory process and the body's attempt to wall off the infection. The presence of these signs suggests that the patient has developed a suppurative tenosynovitis, which is a serious condition that requires prompt medical attention.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as Kanavel's sign is not related to osteoarthritis, which is a degenerative joint disease characterized by cartilage loss and bone-on-bone contact.
**Option B:** This option is incorrect as Kanavel's sign is not associated with tendinitis, which is an inflammation of the tendons, but not the tendon sheath.
**Option C:** This option is incorrect as Kanavel's sign is not a feature of septic arthritis, which is an infection of the joint space.

**Clinical Pearl / High-Yield Fact**
Kanavel's sign is a classic clinical diagnostic criterion that should be remembered by all healthcare professionals, as it is a key indicator of suppurative tenosynovitis, a serious condition that requires prompt medical attention.

**Correct Answer:** D.