Elbow Anatomy
The elbow joint, which appears to be a simple hinge, is actually a sophisticated structure that allows for both bending and rotating movements. It consists of the humerus, which is the bone in the upper arm, and the radius and ulna, which are the two bones in the forearm. These bones work together to provide both stability and a wide range of motion.
Skeletal Anatomy
The elbow in the human body consists of:
- Bones
- Joints
- Muscles
- Ligaments and Tendons
- Numerous Blood vessels, nerves, and soft tissue
In the human body, the arm consists of three bones that together form a hinge joint called the elbow. The upper arm bone, known as the humerus, stretches from the shoulder to the elbow, forming the top part of the hinge joint. The lower part of the arm, referred to as the forearm, contains two bones: the radius and the ulna. These bones run from the elbow to the wrist, making up the lower part of the hinge joint.
The elbow joint is made up of three separate joints that are covered by a sealed membrane called a joint capsule. This capsule surrounds the elbow and contains a lubricating fluid known as synovial fluid.
- Humerus
- Ulna
- Radius
The three joints of the elbow include:
- "Ulnohumeral joint is where movement between the ulna and humerus occurs.
- Radiohumeral jointis where movement between the radius and humerus occurs.
- Proximal radioulnar jointis where movement between the radius and ulna occurs."
Soft Tissue Anatomy
Our elbow is held in place and supported by various soft tissues.
- Cartilage:-
Shiny and smooth, cartilage allows for smooth movement between two bones that touch each other. - Tendons:-
Tendons are soft tissue that connects muscles to bones to provide support. - Biceps
Tendon:-
This tendon connects the biceps muscle located on the front of the arm to the radius bone, enabling supination and rotation of the elbow. - Triceps
Tendon:-
This tendon attaches the triceps muscle on the back of the arm to the ulna bone allowing the elbow to straighten. - Lateral
Epicondyle:-
This bony part, found just above the elbow on the outer side, is where the forearm muscles that extend the fingers and wrist join together in a single tendon to connect to the humerus. - Medial
Epicondyle:-
This bony prominence located just above the elbow on the inside is where the muscles that bend the fingers and wrist come together in one tendon to attach to the humerus. -
Ligaments:-
Ligaments are tough, rope-like tissues that connect bones to other bones and help keep tendons in position, offering support and stability to joints. The ligaments surrounding the elbow come together to form a sealed sac known as a joint capsule. The capsule surrounds the elbow joint and contains synovial fluid, which acts as a lubricant.
There are four main ligaments in the elbow.
- Medial collateral
ligament:-
This ligament is situated on the inner side of the elbow and links the ulna to the humerus. - Lateral collateral
ligament:-
This ligament is situated on the outer side of the elbow and links the radius bone to the humerus bone. - Annular
ligament:-
This ligament creates a ring around the top of the radius bone, keeping it firmly in place against the ulna. - Quadrate
ligament:-
This ligament connects the radius bone to the ulna bone. - Muscles:-
Muscles are made up of fibrous tissue that can contract, which enables movement in the body. - Biceps:-
This is the major muscle on the front of the arm, above the elbow, which helps with supination, or the rotation of the forearm. - Triceps:-
This is the major muscle on the back of the arm, above the elbow, which helps with extending the elbow and straightening it. - Brachialis:-
This muscle mainly helps in bending the elbow. It is found in the lower part of the humerus. - Wrist
extensors:-
The muscles in the forearm attach to the lateral epicondyle, helping to extend the hand and wrist. - Wrist
flexors:-
The muscles in the forearm connect to the medial epicondyle, allowing the hand and wrist to bend. - Nerves:-
Nerves send signals between the brain and muscles throughout the body, allowing for movement and sensations like touch, pain, and temperature.
The three main nerves of the arm are:
- Radial nerve
- Median nerve
- Ulnar nerve
All three nerves start at the shoulder and run down the arm, passing over the elbow.
Blood Vessels
The brachial artery is the main blood vessel in the arm. It travels along the inner part of the elbow near the bend and splits into two separate branches below the joint.
These branches are:
Radial Artery: The radial artery is the main blood vessel that delivers blood to the hand and wrist area. It travels along the front side of the wrist, near the thumb, and it is this artery that you feel when you check your pulse at the wrist.
Ulnar Artery: The ulnar artery travels alongside the ulnar nerve through a passage in the wrist called Guyon’s canal. It delivers blood to the palm and continues into the fingers and thumb.
Bursae
Bursae are small sacs filled with fluid that help reduce friction between tendons, bones, and skin. These sacs contain special cells known as synovial cells, which produce a lubricating fluid. If this fluid becomes infected, it can lead to a painful condition called Bursitis.
Normal Movement
Biomechanics
Biomechanics is the study of how the body moves, including different types of movement and the processes involved.
Flexion
Bending the elbow, which brings the forearm toward the upper arm, happens at the ulnohumeral and radiohumeral joints.
Extension
Straightening the elbow, which moves the forearm away from the upper arm, also takes place at the same joints.
Pronation
One specific movement is the rotation of the forearm, which causes the palm to face downward. This movement occurs at the joint where the radius and ulna bones meet, called the proximal radioulnar joint.
Supination
Similarly, rotating the forearm to make the palm face upward also happens at the proximal radioulnar joint.
