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Olecranon

The olecranon process is the large, curved, proximal projection of the ulna that forms the prominence of the elbow. It extends upward from the shaft of the ulna and articulates with the olecranon fossa of the humerus to form part of the humeroulnar joint. It serves as the lever arm for the triceps brachii muscle and plays a crucial role in elbow extension and stabilization.

The olecranon is easily palpable beneath the skin at the posterior aspect of the elbow and provides attachment for several key muscles, tendons, and ligaments. Its superior surface is smooth and concave, contributing to the trochlear notch, while the posterior surface is subcutaneous and often a site of bursitis or fracture.

Synonyms

  • Olecranon of the ulna

  • Proximal ulnar process

  • Elbow tip

Location and Structure

  • Situated at the proximal end of the ulna, forming the upper part of the trochlear notch

  • Projects upward and backward behind the elbow joint

  • Articular surface: Smooth and concave anteriorly, articulating with the trochlea of the humerus

  • Posterior surface: Subcutaneous and rough, covered only by skin and olecranon bursa

  • Superior border: Rounded and curved for the triceps tendon attachment

  • Inferior continuation: Joins the coronoid process forming the semilunar (trochlear) notch

Relations

  • Posteriorly: Subcutaneous tissue, olecranon bursa, and skin of the posterior elbow

  • Anteriorly: Olecranon fossa of humerus and elbow joint capsule

  • Superiorly: Triceps brachii tendon insertion

  • Inferiorly: Coronoid process and trochlear notch

  • Laterally: Anconeus muscle and lateral collateral ligament complex

  • Medially: Ulnar collateral ligament and flexor carpi ulnaris tendon

Attachments

  • Triceps brachii: Inserts onto the posterior and superior surface of the olecranon process, serving as the primary extensor of the elbow

  • Anconeus: Attaches along the lateral margin

  • Ulnar collateral ligament: Medial aspect of the olecranon provides attachment for the posterior portion of the ligament

  • Capsular attachments: Anterior and lateral surfaces contribute to the posterior wall of the elbow joint capsule

Function

  • Lever arm for extension: Serves as the insertion point for triceps brachii, facilitating elbow extension

  • Joint stability: Forms posterior part of the trochlear notch, preventing posterior displacement of the ulna

  • Protection: Acts as a bony shield for the posterior elbow joint

  • Muscle attachment site: Provides origin and insertion areas for several muscles stabilizing the elbow

  • Articulation: Engages with humeral trochlea for hinge-like motion at the elbow joint

Clinical Significance

  • Fractures: Common due to direct trauma or falls on the elbow; classified based on displacement and involvement of articular surface

  • Olecranon bursitis: Inflammation of the subcutaneous bursa due to repetitive trauma (“student’s elbow”)

  • Triceps avulsion: Forceful contraction or injury may cause detachment of triceps tendon with olecranon fragment

  • Osteophyte formation: Chronic stress may cause posterior spur development, especially in throwing athletes

  • Post-surgical relevance: Important landmark for internal fixation, olecranon osteotomy, and total elbow arthroplasty

  • Imaging importance: MRI and CT are key for assessing fractures, bursitis, and soft-tissue attachments

MRI Appearance

  • T1-weighted images:

    • Cortex: Low signal (dark)

    • Bone marrow: Bright (fatty marrow signal in adults)

    • Articular surface: Smooth, low-signal cortical line forming trochlear notch

    • Triceps tendon: Low-signal band inserting at the olecranon apex

    • Olecranon bursa: Usually not visible unless distended; appears as thin low-signal line

  • T2-weighted images:

    • Cortex: Low signal

    • Bone marrow: Bright, though less than on T1

    • Triceps tendon: Low signal, continuous from muscle to insertion

    • Bursa: Distended or inflamed bursa appears hyperintense

    • Fracture or marrow edema: Bright hyperintensity interrupting cortical outline

  • STIR:

    • Normal marrow: Intermediate-to-dark signal

    • Pathology: Bright signal with indistinct trabeculae indicating edema, stress reaction, or fracture

    • Bursitis or soft-tissue swelling: Marked hyperintensity posterior to olecranon

  • Proton Density Fat-Saturated (PD FS):

    • Normal bone: Intermediate-to-dark signal

    • Pathologic areas: Bright hyperintensity from edema or inflammation

    • Ideal for detecting partial tendon tears, bursitis, or periosteal reaction

  • T1 Fat-Sat Post-Contrast:

    • Normal bone and tendon: Minimal enhancement

    • Bursitis: Peripheral rim enhancement around fluid-filled sac

    • Infection or osteomyelitis: Patchy marrow enhancement and cortical disruption

    • Tendon inflammation: Linear or diffuse enhancement along triceps insertion

CT Appearance

Non-Contrast CT:

  • Cortex: High-attenuation dense outline forming the posterior ulna

  • Trabecular bone: Fine internal structure with uniform pattern

  • Articular surface: Smooth contour articulating with humeral trochlea

  • Pathology: Fractures, avulsion fragments, or bony spurs easily visualized

  • Detects bony irregularity, cortical discontinuity, and post-traumatic deformity with precision

Post-Contrast CT (standard):

  • Normal bone: Homogeneous cortical enhancement minimal to absent

  • Inflammatory or infectious conditions: Enhanced periosteum or bursa

  • Postoperative imaging: Highlights soft-tissue healing, effusion, or hardware complications

CT VRT 3D image

olecranon process of ulna 3D VRT IMAGE

MRI image

olecranon process of ulna axial cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000

MRI image

olecranon process of ulna sag cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000

CT image

olecranon process of ulna coronal ct image

CT image

olecranon process of ulna sag ct image