The wrist is a complex joint that marks the transition between the forearm and hand. It has many components, allowing it to do a range of movements.
The radiocarpal joint is sometimes referred to as the wrist joint. But it’s actually one of two joints in the wrist, the other being the midcarpal joint. The radiocarpal joint is where the radius bone of the forearm meets the first row of carpal bones in the lower hand.
The radiocarpal joint itself cannot rotate. It can only move side to side and up and down.
Its other movements include:
- Flexion. This is the movement created when the wrist is bent so that the palm of the hand is angled closer to the inside of the wrist.
- Extension. The opposite of flexion, this movement raises the back of the hand so that it’s closer to the top of the wrist and forearm.
- Radial deviation. This movement involves tilting the wrist toward the thumb.
- Ulnar deviation. This movement occurs when the wrist is tilted toward the little finger.
The radiocarpal joint has many parts, including bones and ligaments, that help it function as one of the most used joints in the body.
The radiocarpal joint is made up of four bones:
The radius is one of the two bones of the forearm. It’s found on the same side of the forearm as the thumb. It can twist around the other bone of the forearm, the ulna, depending on how the hand is positioned.
The scaphoid is found in the first row of carpal bones. It’s the one that’s closest to the thumb. The majority of the scaphoid is covered by cartilage, except in the areas where ligaments and blood vessels are located.
The lunate bone is found between the scaphoid and triquetrum bones. It’s also mostly covered in cartilage.
The triquetrum bone is the last bone found in the first row of carpal bones. It’s located closest to the pinky finger. It helps to stabilize the wrist and allows the joint to bear more weight.
Although the second bone of the forearm, the ulna, articulates with the radius, it’s separated from the wrist joint by a disc of fibrocartilage called the articular disk.
There are four main ligaments in the radiocarpal joint — one for each side of the joint. They work together to stabilize the radiocarpal joint.
The main ligaments of the radiocarpal joint include the:
Dorsal radiocarpal ligament
This ligament is found on the top of the wrist joint, closest to the back of the hand. It attaches to the radius and both rows of carpal bones. It helps to protect the wrist from extreme flexing movements.
Palmar radiocarpal ligament
This is the thickest wrist ligament. It’s found on the side of the wrist closest to the palm of the hand. Like the dorsal radiocarpal ligament, it attaches to the radius and both rows of carpal bones. It works to resist extreme extension movements of the wrist.
Radial collateral ligament
The radial collateral ligament is located on the side of the wrist closest to the thumb. It attaches at the radius and scaphoid and works to prevent excessive side-to-side movement of the wrist.
Ulnar collateral ligament
This ligament is located on the side of the wrist closest to the pinky finger. It attaches at the ulna and the triquetrum. Like the radial collateral joint, it prevents excessive side-to-side movement of the wrist.
The radiocarpal joint is enclosed in something called a joint capsule. The capsule consists of an inner and outer layer:
- The outer layer of the joint capsule is fibrous and connects to the radius, ulna, and first row of carpal bones.
- The inner layer of the capsule is more membranous. It secretes a viscous fluid called synovial fluid. The synovial fluid reduces friction between the different components of the joint and helps them to move smoothly.
Explore the interactive 3-D diagram below to learn more about the radiocarpal joint:
A variety of conditions can cause pain at or around the radiocarpal joint, including:
Wrist injuries can happen when you stretch your hand out to break a fall. When you do this, your wrist takes the brunt of the impact, potentially leading to a sprain or fracture.
Performing activities that repeatedly place stress, such as hitting a tennis ball, on the wrist can cause irritation and inflammation at the joint, leading to pain.
Arthritis occurs when the tissues that protect your joints break down, leading to swelling, pain, and decreased range of motion. This can occur due to degradation of cartilage (osteoarthritis) or by the immune system attacking joint tissues (rheumatoid arthritis).
Carpal tunnel syndrome
Carpal tunnel syndrome occurs when the median nerve, which passes through the wrist, becomes pinched or compressed. The numbness, tingling, or pain from carpal tunnel syndrome is often felt in the hand and fingers, but can also be present around the wrist.
Bursae are small sacs that act as a cushion for the moving parts of your body, including bones, muscles, and tendons. You have bursae throughout your body, including around your wrist. Bursitis occurs when a bursa becomes irritated or inflamed due to injury, repeated use of a joint, or an underlying condition.
If a cyst forms in or around the radiocarpal joint, it can put pressure on the surrounding tissues, causing pain.
In this condition, the lunate bone loses its supply of blood, which causes the bone to die. This can lead to pain, swelling, and loss of motion in the wrist. Experts aren’t sure what causes Kienbock’s disease. This condition is also known as avascular necrosis of the lunate.