Hand & Wrist Anatomy

The hand in the human body is made up of the wrist, palm, and fingers. The most flexible part of the human skeleton, the hand enables us to perform many of our daily activities. When our hand and wrist are not functioning properly, daily activities such as driving a car, bathing, and cooking can become impossible.

The hand’s complex anatomy consists of 27 bones, 27 joints, 34 muscles, over 100 ligaments and tendons, numerous blood vessels, nerves, and soft tissue.

The wrist is comprised of 8 bones called carpal bones. These wrist bones connect to 5 metacarpal bones that form the palm of the hand. Each metacarpal bone connects to one finger or a thumb at a joint called the metacarpophalangeal joint, or MCP joint. This joint is commonly referred to as the knuckle joint.

The bones in our fingers and thumb are called phalanges. Each finger has 3 phalanges separated by two joints. The first joint, closest to the knuckle joint, is the proximal interphalangeal joint or PIP joint. The second joint nearer the end of the finger is called the distal interphalangeal joint, or DIP joint. The thumb in the human body only has 2 phalanges and one interphalangeal joint.

Our hand and wrist bones are held in place and supported by various soft tissues. These include

Cartilage: Shiny and smooth, cartilage allows smooth movement where two bones come in contact with each other.

Tendons: Tendons are soft tissue that connects muscles to bones to provide support. Extensor tendons enable each finger to straighten. Flexor tendons enable each finger to bend.

Ligaments: Ligaments are strong rope like tissue that connects bones to other bones and help hold tendons in place providing stability to the joints. The volar plate is the strongest ligament in the hand and prevents hyperextension of the PIP joint.

Muscles: Muscles are the fibrous tissues capable of contracting to cause body movement.

Interestingly, the fingers contain no muscles. Small muscles originating from the carpal bones of the wrist are connected to the finger bones with tendons. These muscles are responsible for movement of the thumb and little finger enabling the hand to hold and grip items by allowing the thumb to move across the palm, a movement referred to as thumb opposition. The smallest muscles of the wrist and hand are responsible for fine motor movement of the fingers.

Nerves: Nerves are responsible for carrying signals back and forth from the brain to muscles in our body, enabling movement and sensation such as touch, pain, and hot or cold. The three main nerves responsible for hand and wrist movement all originate at the shoulder area and include the following

• Radial nerve
• Median nerve
• Ulnar nerve

Bursae: Bursae are small fluid filled sacs that decrease friction between tendons and bone or skin. Bursae contain special cells called synovial cells that secrete a lubricating fluid. When this fluid becomes infected, a common painful condition known as bursitis can develop.