The inside of the elbow, often called the elbow crease, is an anatomical depression formally known as the cubital fossa or antecubital fossa. This triangular area houses important structures that facilitate movement and blood flow in the forearm. Understanding this space provides insight into common medical procedures and the complex anatomy of the arm.
Defining the Cubital Fossa
The cubital fossa is a shallow, triangular hollow located on the anterior side of the elbow joint. It is often referred to as the elbow crease. The alternative term “antecubital fossa” means “in front of the elbow,” which is why both names are used interchangeably. This depression serves as a protected passage for structures moving between the upper arm and the forearm.
The boundaries of this region are defined by three muscular borders. The lateral side is formed by the brachioradialis muscle, which runs along the thumb side of the forearm.
The medial boundary is created by the pronator teres muscle. The superior boundary is an imaginary horizontal line connecting the medial and lateral epicondyles of the humerus, marking the base of the triangle.
The floor of the fossa is formed by the deeper brachialis and supinator muscles. The roof is comprised of the skin and a layer of fascia, reinforced by the bicipital aponeurosis. This arrangement creates a safe yet accessible conduit for the neurovascular bundles passing through.
Critical Structures Contained Within
The cubital fossa contains several structures, arranged in sequence from the outer edge to the inner edge. Located most laterally is the tendon of the biceps brachii muscle. This tendon inserts into the radius bone.
Next to the tendon lies the brachial artery, the primary blood vessel of the arm. As the artery passes through the fossa, it divides into the radial and ulnar arteries, which supply blood to the forearm and hand.
The median nerve runs through the middle of the fossa, positioned medially to the brachial artery. This nerve innervates many muscles that flex the wrist and fingers. It also provides sensory information to the skin of the hand.
While the artery and nerve run deep, the area also features a network of superficial veins located closer to the skin. These vessels are visible through the roof of the fossa.
The most prominent surface vessel is the median cubital vein, which crosses diagonally over the fossa. This vein bridges the cephalic vein (lateral side) and the basilic vein (medial side) of the forearm.
Clinical Significance of the Elbow Crease
The predictable arrangement of neurovascular structures makes the cubital fossa a significant site in clinical medicine. Its superficial veins provide the most common access point for drawing blood (phlebotomy). The median cubital vein is particularly useful because it is typically wide and does not move excessively when a needle is inserted.
This stability also makes the fossa the standard location for establishing intravenous access. The large volume of blood flow ensures that administered fluids or medications are quickly distributed throughout the body.
The brachial artery’s presence beneath the skin is utilized during blood pressure measurement. A cuff is inflated around the upper arm to temporarily occlude the artery. A stethoscope is then placed over the artery in the fossa to listen for the Korotkoff sounds.
These sounds indicate the systolic and diastolic pressures as the cuff is slowly deflated. The cubital fossa can also be used in emergency situations to quickly assess circulation by checking the brachial pulse.