What are the main types of joints in the hand?

The hand has three main joint groups: intercarpal joints (plane synovial joints between carpal bones), carpometacarpal (CMC) joints (connecting carpal and metacarpal bones), and intermetacarpal joints (plane joints between metacarpal bases). These enable fine, coordinated movements.

Why is the thumb's carpometacarpal joint so mobile?

The first CMC joint (thumb) is a saddle-type synovial joint with reciprocally concavo-convex surfaces between the trapezium and first metacarpal. This unique structure allows a wide range of motion, including opposition, unlike the less mobile plane joints of other CMC joints.

How do the carpometacarpal joints differ in mobility?

CMC joint mobility varies by location: 1st CMC (thumb) is highly mobile (saddle joint), 2nd–3rd CMC are almost immobile, 4th CMC is slightly mobile, and 5th CMC is moderately mobile. This gradation supports hand dexterity and grip.

What are the key ligaments of the thumb's carpometacarpal joint?

The first CMC joint is stabilized by several ligaments: capsular ligament (loose, fibrous capsule), lateral ligament (trapezium to lateral base of 1st metacarpal), and palmar and dorsal ligaments (trapezium to ulnar base of 1st metacarpal). These help control movement and joint integrity.

What movements are possible at the thumb's carpometacarpal joint?

The first CMC joint enables multiple movements: flexion/extension, abduction/adduction, opposition, medial/lateral rotation, and circumduction. This versatility is crucial for tasks like grasping and pinching.

How are the joint cavities organized in the hand?

Hand joint cavities are divided into three main groups: a large common cavity for most intercarpal and CMC joints (except 1st CMC), a separate cavity for the 1st carpometacarpal joint (thumb), and a separate cavity for the pisotriquetral joint. This separation helps isolate movements and reduce friction.

What structures are related to the thumb's carpometacarpal joint?

The first CMC joint is surrounded by thumb muscles and tendons, with the radial artery on its posteromedial side and the first dorsal interosseous muscle medially. It is supplied by the radial artery and median nerve.

Hand Joints – Carpal, CMC & Thumb Saddle Joint

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