What is radial tunnel syndrome?

Radial tunnel syndrome is a painful condition due to compression neuropathy of the posterior interosseous nerve. There is no sensory or motor deficit.

Anatomy of the Radial Tunnel

Radial tunnel refers to a region extending from the radiocapitellar joint to past the proximal origin of the supinator. 

Potential sites of compression (mnemonic "FREAS")

  • Fibrous band anterior to the radiocapitellar joint
  • Recurrent vessels (Leash of Henry)
  • ECRB medial edge
  • Arcade of Frohse (aponeurotic edge of supinator)
  • Supinator distal edge


  • Deep aching pain in the proximal dorsoradial forearm
    • made worse by forearm rotation and lifting
  • The following provocative tests may reproduce the symptom but they are not specific enough and may be confused with lateral epicondylitis
    • Passive pronation with wrist flexion
    • Resisted supination with elbow/wrist in extension
    • Resisted long finger extension
  • The most reliable sign is perhaps the exact location of maximal tenderness. In radial tunnel syndrome, the tender point is more distal than that of lateral epicondylitis (tennis elbow). The former is maximally tender at 3-5cm distal to the lateral epicondyle while the latter is maximally tender directly over or at 1cm distal to the lateral epicondyle. Both conditions however co-exist.


  • MRI is used for exclusion of structural anomalies around the nerve. This is typically normal in radial tunnel syndrome.
  • NCS/EMG are also typically normal.



  • Activity modification & painkillers
  • This is the mainstay of treatment 


  • Radial tunnel release/decompression 

Key Message

  • Radial tunnel syndrome is essentially a pain syndrome while PIN palsy is associated with motor deficit
   Radial Tunnel Syndrome  PIN Palsy
 Symptom  Vague, deep seated pain at the proximal forearm  Pain may not be a prominent feature
 Motor deficit  No motor deficit  Weakness/paralysis of muscles
 Sensory deficit  No sensory deficit  No sensory deficit
 MRI  Normal

To exclude lesion (lipoma, ganglion)

Muscles may show denervated signals

 NCS/EMG  Normal  Abnormal
 Treatment  Nonoperative treatment is favoured. Close monitoring for progressive weakness 
 Surgery  High threshold to decompress the nerve  Low threshold to decompress the nerve


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