Hand and Wrist Joint
Anatomy & Function
Dr. Pamela Mehta, MD
Hand and Wrist Joint Anatomy
Your hand and wrist are a complex and intricate part of your musculoskeletal system, composed of many different muscles, bones, and ligaments. There are numerous joints between the bones in your hand and wrist, all of which can be affected by arthritis, injury, and other hand conditions.
Your hands have a great amount of dexterity that allow you to perform everyday tasks. Without the complex hand and wrist joints, you wouldn’t be able to use tools, hold your cell phone, or do any of the day-to-day activities we take for granted.
Your hand and wrist are comprised of 29 bones.
- The Radius. The large bone of your forearm that connects your elbow to your wrist.
- The Ulna. The smaller bone of your forearm, going from the elbow to the wrist.
- The Carpals. Eight irregular bones in your wrist and palm, organized into two rows. These bones lie between the bones of the forearm (radius and ulna) and the metacarpal bones in the hand.
- The Metacarpals. Five long bones which connect the carpals to the phalanges.
- The Phalanges. The bones which make up your fingers and thumb. Your fingers each have three phalanges, whereas your thumb has two.
Joints of the Hand
For the hand to grip, hold and touch, it has joints between each of the hand and wrist bones. These joints are lined with articular cartilage, also known as chondral cartilage, which allow them to move smoothly against each other. Hand osteoarthritis occurs when the cartilage is damaged over time due to wear and tear, causing pain and inflammation.
The wrist joints include the radiocarpal joint, the ulnocarpal joint, the distal radioulnar joint. These joints connect the bones of the forearm (the radius and ulna) with the carpal bones. The wrist can twist and tilt, allowing your hand to manage difficult positions.
Carpal Joints are the joints that connect your carpal bones to each other.
Carpometacarpal Joints (CMC joints) are the joints which connect the furthest five carpal bones to your metacarpal bones.
Metacarpophalangeal Joints (MCP Joints) are the joints between your metacarpal bones and the proximal phalanges.
Proximal Interphalangeal Joints (PIP Joints) are the joints between your proximal phalanges and your intermediate phalanges. In your thumb this joint is called the interphalangeal joint (IP).
Distal Interphalangeal Joints (DIP Joints) are the joints between your intermediate phalanges and your distal phalanges. The thumb doesn’t have a DIP joint.
Your wrist has four key ligaments:
- Palmar radiocarpal ligament – connects the radius to both rows of the carpal bones, on the front side of the hand.
- Dorsal radiocarpal ligament – connects the radius to both rows of the carpal bones, on the back side of the hand.
- Ulnar collateral ligament – connects the ulna bone to the triquetrum and pisiform bones (two of your carpal bones).
- Radial collateral ligament – connects your radius bone to the scaphoid and trapezium (two of your carpal bones).
Hand and Wrist Muscles
To help your hand and wrist make complex movements, there are many muscles in both the forearm and the hand itself that move your wrist, hand, fingers, and thumb.
Thenar muscles are three muscles that form the bulge (thenar eminence) in your palm at the base of your thumb. These muscles control the fine movements of your thumb.
Hypothenar muscles are three muscles that form the bulge (hypothenar eminence) in your palm at the base of your little finger. These muscles control the movements of your little finger.
Lumbrical muscles are four muscles on the back of the hand, each attaching to a finger. These muscles help with the bending and straightening of all your fingers.
Interossei muscles are seven muscles that lie between each finger’s metacarpal bones, on the front and back side of your hand. These muscles help you fan out your fingers and bring them back together again, as well as helping with the bending and straightening of your fingers.
Your hand also includes the palmaris brevis muscle which helps with grip, and the adductor pollicis muscle which helps to bring the thumb back towards the hand when it is fanned out.
Hand and Wrist Muscles
The muscles in your forearm are also key to your hand and wrist movements. Some muscle tendons from the forearm pass through the wrist to bend and straighten the fingers and thumb, with others passing down the side of your wrist. Trigger finger affects the tendons which pass through your wrist, and de Quervain’s tenosynovitis affects the tendons at the side of your wrist.
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