A lady having flexion at proximal interphalyngeal joint and hyperextension at distal interphalyngeal joint of index finger is called-
**Core Concept**
The question is testing the student's knowledge of joint deformities, specifically the characteristic posture of the hand in a particular condition. The underlying principle involves the abnormal alignment of joints in the hand.
**Why the Correct Answer is Right**
The condition described is characteristic of mallet finger, a type of flexor tendon injury. When the extensor tendon of the distal interphalangeal (DIP) joint is ruptured, the finger cannot extend, leading to hyperextension at the DIP joint. Simultaneously, the flexor tendon of the proximal interphalangeal (PIP) joint contracts, resulting in flexion at the PIP joint.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the condition described. The characteristic posture of mallet finger involves hyperextension at the DIP joint and flexion at the PIP joint, which is not seen in this option.
* **Option B:** This option may refer to a different condition, such as a swan neck deformity, where the PIP joint is hyperextended and the DIP joint is flexed. This is not the same as the condition described in the question.
* **Option C:** This option may refer to a condition where the finger is flexed at both the PIP and DIP joints, which is not consistent with the description provided.
**Clinical Pearl / High-Yield Fact**
Mallet finger is often caused by a direct blow to the DIP joint, such as when a ball hits the finger. It can also occur due to a sudden contraction of the flexor tendon, such as when catching a ball.
**Correct Answer: C. Mallet finger**