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Common flexor tendon

The common flexor tendon (CFT) is the shared tendinous origin of the superficial flexor muscles of the forearm, attaching to the medial epicondyle of the humerus. It serves as the proximal anchor for muscles that flex the wrist and fingers and pronate the forearm. The tendon forms part of the flexor-pronator mass, a key stabilizing structure of the medial elbow.

This tendon is clinically important as the site of medial epicondylitis (“golfer’s elbow”), tendinopathy, and partial-thickness tears. It plays a vital biomechanical role in grip strength, wrist flexion, and dynamic stabilization of the medial elbow during repetitive motion.

Synonyms

  • Flexor-pronator common tendon

  • Medial epicondylar tendon origin

  • Common tendon of forearm flexors

Origin, Course, and Insertion

  • Origin: Medial epicondyle of the humerus via a strong tendinous attachment

  • Course: Fibers blend with those of the flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and pronator teres as they descend into the forearm

  • Insertion: Though not inserting distally as a single tendon, the CFT serves as a proximal aponeurotic origin for multiple flexor muscles that insert along the radius, ulna, and metacarpals

Tendon Attachments

  • Firmly attached to the anterior inferior aspect of the medial epicondyle

  • Continuous with the medial intermuscular septum and antebrachial fascia

  • Tendinous fibers intermingle with the joint capsule and ulnar collateral ligament (UCL), contributing to elbow stability

Relations

  • Superficial: Subcutaneous tissue and skin over medial elbow

  • Deep: Ulnar collateral ligament, elbow joint capsule, and humerus

  • Medially: Ulnar nerve passing posterior to the medial epicondyle

  • Laterally: Pronator teres muscle fibers

  • Anteriorly: Overlapped by flexor-pronator muscle belly

Muscles Originating from the Common Flexor Tendon

  • Pronator teres (humeral head)

  • Flexor carpi radialis

  • Palmaris longus

  • Flexor carpi ulnaris (humeral head)

  • Flexor digitorum superficialis (humeroulnar head)

Arterial Supply

  • Branches of the ulnar and radial arteries, primarily via the inferior ulnar collateral and recurrent branches, providing small penetrating vessels to the tendon

Function

  • Flexion: Assists in wrist and finger flexion

  • Pronation: Aids in pronation through pronator teres contribution

  • Medial elbow stabilization: Resists valgus stress in coordination with the UCL

  • Force transmission: Transfers tensile loads from the forearm flexors during gripping and lifting

  • Joint integrity: Maintains medial elbow alignment during repetitive activities

Clinical Significance

  • Medial epicondylitis (Golfer’s elbow): Overuse injury causing microtears and degeneration at the tendon’s humeral origin

  • Partial or complete tear: From acute traction or repetitive valgus loading, seen in throwing athletes

  • Tendinopathy: Chronic degeneration with mucoid change or fibrosis

  • Avulsion fractures: Rare, usually in adolescents following strong muscular contraction

  • Surgical relevance: Important landmark during UCL reconstruction and tendon debridement procedures

MRI Appearance

  • T1-weighted images:

    • Normal tendon: low signal intensity (dark, homogeneous band) attaching to the medial epicondyle

    • Adjacent bone marrow: bright fatty signal

    • Pathology: intermediate-to-bright signal in partial tears or tendinopathy; tendon thickening and indistinct margins

  • T2-weighted images:

    • Normal tendon: low-to-intermediate signal, clearly defined against brighter muscle and fat

    • Tendinopathy: focal or diffuse hyperintense signal within tendon, often with thickening

    • Partial tear: bright linear or globular hyperintensity extending to cortical insertion

    • Surrounding soft-tissue edema and mild joint effusion may be present

  • STIR:

    • Normal tendon: dark to intermediate signal

    • Pathology: bright hyperintense signal indicating edema or partial tear

    • Useful for differentiating inflammatory tendinitis from chronic scarring

  • Proton Density Fat-Saturated (PD FS):

    • Normal: uniformly dark tendon

    • Partial-thickness tear: bright intratendinous signal and cortical irregularity

    • Chronic degeneration: irregular thickening, heterogeneous signal intensity, and surrounding peritendinous edema

  • T1 Fat-Sat Post-Contrast:

    • Normal tendon: minimal to no enhancement

    • Acute tendinitis or partial tear: shows focal or diffuse enhancement due to hypervascular granulation tissue

    • Chronic tendinopathy: mild peripheral enhancement surrounding low-signal fibrotic areas

CT Appearance

Non-Contrast CT:

  • Common flexor tendon not distinctly visualized as a separate structure due to soft-tissue similarity

  • Calcific tendinitis: appears as localized hyperdense calcification near the medial epicondyle

  • Avulsion fractures: visualized as small bone fragments at tendon origin

Post-Contrast CT (standard):

  • Normal tendon: uniform soft-tissue density

  • Inflammation or acute injury: mild enhancement at medial epicondyle attachment

  • Chronic changes: thickened tendon with irregular contour and adjacent cortical sclerosis

MRI image

Common flexor tendon axial cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000

MRI image

Common flexor tendon axial cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000_00001

MRI image

Common flexor tendon axial cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000_00002

MRI image

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MRI image

Common flexor tendon coronal cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000