AssessmentsJoints of the wrist and hand
Joints of the Wrist and Hand
Content Reviewers:Scott Caterine, BSc (Hons.), MSc, MB, BCh, BAO (Hons.), Viviana Popa, MD
The wrist is a complex joint that serves as the bridge connecting the forearm and the hand together.
Try saying those three times fast!!
Ok, let’s start with the wrist joint.
The articulating surfaces of the radiocarpal joint are surrounded by the tough joint capsule and synovial membrane, extending from the distal ends of the radius and ulna, to the scaphoid, the lunate, and the triquetrum.
The joint capsule of the radiocarpal joint is reinforced by a couple of ligaments, both on the dorsal and the palmar sides of the joint.
The palmar ligaments extend from the distal radius to the two rows of the carpal bones.
These ligaments strengthen the joint and make it possible for the hand and the radius to move as one unit during supination of the forearm, or turning the palm upwards.
To remember this, think about cupping both your hands and bringing them together to hold a bowl of ‘soup’, which mimics the movement of supination.
Other ligaments that strengthen the radiocarpal joint are the ulnar collateral ligament on the medial side, which extends from the ulnar styloid process to the triquetrum; and the radial collateral ligament on the lateral side, extending from the radial styloid process to the scaphoid bone.
Now, a couple of muscles act on the radiocarpal joint.
So there’s the flexor carpi radialis and the flexor carpi ulnaris, which flex the wrist; the extensor carpi radialis longus, the extensor carpi radialis brevis, and the extensor carpi ulnaris which extend the wrist; the abductor pollicis longus, the flexor carpi radialis, the extensor carpi radialis longus, and the extensor carpi radialis brevis which abduct or radially deviate the wrist; and then finally, the extensor carpi ulnaris and the flexor carpi ulnaris muscles which adduct or ulnar deviate the wrist.
Regarding innervation, remember Hilton’s law, which says the nerves that innervate the muscles crossing over a particular joint also innervate that joint.
They can be put into four groups to make things simple.
There are joints between the carpal bones of the proximal row; the joints between the carpal bones of the distal row; the midcarpal joint between the proximal and distal rows of carpal bones; and the pisotriquetral joint located between the pisiform and the palmar surface of the triquetrum.
Though this sounds like a minor role, these joints are important because their combined little movements augment the range of motion of the radiocarpal joint.
Sometimes less is more!
The first carpometacarpal joint is responsible for the movements of the thumb, and consists of the trapezium and the first metacarpal bone, which is the only saddle type of synovial joint of the carpometacarpal joints.
The wrist is a complex joint that connects the hand to the forearm. It consists of the radiocarpal joint found between the radius and the proximal row of the carpal bones except for the pisiform; and the intercarpal joints, which are small joints among the carpals.
Joints of the hand include carpometacarpal joints found between the carpals and the metacarpals; the intermetacarpal joints among the metacarpals themselves; the metacarpophalangeal joints between the metacarpals and the proximal phalanges; and finally, the interphalangeal joints found between the proximal phalanges and the middle or distal phalanges.