In the hand anatomy, Structure I corresponds to which joint?

In the hand anatomy, Structure I corresponds to which joint?

• A. Second proximal interphalangeal joint
• B. First carpometacarpal joint
• C. Second distal interphalangeal joint
• D. Second metacarpophalangeal joint

Answer: (A)

The joints of the fingers and thumb have distinct locations that let you identify them on a hand diagram. The joint between the proximal and middle phalanges is the proximal interphalangeal joint, and for the index finger this is the second digit’s PIP joint. Structure I sits at that mid‑finger location, so it corresponds to the proximal interphalangeal joint of the second finger. Understanding the others helps place them: the first carpometacarpal joint is at the base of the thumb, the second distal interphalangeal joint is between the middle and distal phalanges near the fingertip, and the second metacarpophalangeal joint is the knuckle between the index finger’s proximal phalanx and the second metacarpal.

The joints of the fingers and thumb have distinct locations that let you identify them on a hand diagram. The joint between the proximal and middle phalanges is the proximal interphalangeal joint, and for the index finger this is the second digit’s PIP joint. Structure I sits at that mid‑finger location, so it corresponds to the proximal interphalangeal joint of the second finger.

Understanding the others helps place them: the first carpometacarpal joint is at the base of the thumb, the second distal interphalangeal joint is between the middle and distal phalanges near the fingertip, and the second metacarpophalangeal joint is the knuckle between the index finger’s proximal phalanx and the second metacarpal.