Cubital fossa
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Here is a complete account of the cubital fossa from Gray's Anatomy for Students.
Cubital Fossa
Definition and Location
The cubital fossa is a triangular depression on the anterior aspect of the elbow joint, representing the transition zone between the arm and the forearm. "Cubital" refers to the elbow (Latin: cubitus).
Boundaries
| Component | Structure |
|---|---|
| Base (superior) | Imaginary horizontal line connecting the medial and lateral epicondyles of the humerus |
| Lateral border | Brachioradialis muscle (originates from the lateral supraepicondylar ridge) |
| Medial border | Pronator teres muscle (originates from the medial epicondyle) |
| Apex (inferior) | Where brachioradialis and pronator teres meet distally |
| Floor (bed) | Brachialis muscle (mainly) + supinator laterally |
| Roof | Superficial fascia and skin; reinforced by the bicipital aponeurosis deep to it |
The pronator teres margin can be estimated clinically by a line from the medial epicondyle to the midpoint of the lateral forearm surface. The apex is where this line intersects the brachioradialis margin.
Contents (Lateral to Medial) - "TAN"
A useful mnemonic: T-A-N (Tendon - Artery - Nerve)
- Tendon of biceps brachii - easily palpable; sends the bicipital aponeurosis medially
- Brachial artery - bifurcates into radial and ulnar arteries at the apex of the fossa
- Median nerve - immediately medial to the brachial artery; exits by passing between the two heads of pronator teres
The radial nerve lies just deep to the brachioradialis along the lateral wall (not classically in the "TAN" trio) and divides here into:
- Superficial branch - continues under brachioradialis into the forearm
- Deep branch (posterior interosseous nerve) - passes between the two heads of the supinator into the posterior compartment
The ulnar nerve does NOT pass through the cubital fossa. It passes posterior to the medial epicondyle, where it can be palpated against the bone.
Diagrams
Fig. 7.77 - Cubital Fossa (Gray's Anatomy for Students): (A) Margins, (B) Contents, (C) Radial nerve position, (D) Superficial structures
Fig. 7.121 - Cubital Fossa, anterior view (right arm): (A) Boundaries, (B) Contents, (C) Nerves and veins
Roof in Detail - The Bicipital Aponeurosis
The bicipital aponeurosis (lacertus fibrosus) is a flat connective tissue sheet that fans off the medial side of the biceps brachii tendon and blends into the deep fascia of the forearm. It covers and protects the brachial artery and median nerve in the distal cubital fossa. Its sharp medial margin can usually be palpated.
Superficial Structures in the Roof
In the subcutaneous fascia overlying the fossa:
- Median cubital vein - passes diagonally across the roof connecting the cephalic and basilic veins. This is the most common site for venepuncture and IV cannulation.
- Cephalic vein - lateral
- Basilic vein - medial
- Lateral cutaneous nerve of the forearm (terminal branch of musculocutaneous nerve) - lateral
- Medial cutaneous nerve of the forearm - medial
Clinical Relevance
| Scenario | Relevance |
|---|---|
| Blood pressure measurement | Brachial artery lies here - stethoscope placed over it for auscultation of Korotkoff sounds |
| Venepuncture / IV access | Median cubital vein in the roof is the standard site |
| Brachial artery pulse | Palpable medial to the biceps tendon |
| Brachial artery bifurcation | Normally occurs at the apex; may occur higher (even in axilla) as a variant |
| IV drug use | Repeated injections in the cubital fossa cause scarring ("railroad track" pigmented scars) and thrombosed veins |
| Dialysis fistula | Brachial artery anastomosed to cephalic vein at the elbow to create high-flow access |
| Pronator teres syndrome | Compression of median nerve between the heads of pronator teres as it exits the fossa |
| Ulnar nerve entrapment | Occurs at the cubital tunnel (posterior to medial epicondyle), NOT inside the cubital fossa |
Summary Table
| Feature | Detail |
|---|---|
| Shape | Triangle |
| Location | Anterior elbow |
| Base | Intercondylar line |
| Lateral wall | Brachioradialis |
| Medial wall | Pronator teres |
| Floor | Brachialis + supinator |
| Roof | Skin + fascia + bicipital aponeurosis |
| Contents (L to M) | Biceps tendon, Brachial artery, Median nerve (TAN) |
| Radial nerve | Under brachioradialis (not in classic contents) |
| Ulnar nerve | NOT in fossa - runs behind medial epicondyle |
- Gray's Anatomy for Students, pp. 889-890, 944-945
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