This blog article on “Supinator Syndrome” is an excerpt from the Sports Medicine Acupuncture: An Integrated Approach Combining Sports Medicine with Traditional Chinese Medicine textbook available from smatextbook.com.
The Great Imitator for Lateral Epicondylitis
Figure 1. Increased tension in the supinator muscle can entrap the posterior interosseous nerve.
The deep radial nerve, also known as the posterior interosseous nerve, is a lateral branch extending off of the radial nerve in the region of LI 11 (quchi). The posterior interosseous nerve covers the ulnar side of the forearm along the pathway of the San Jiao channel. The nerve is susceptible to entrapment where it passes through a fibrous narrow channel called the arcade of Frohse (Fig. 1). This entrapment site is located deep to the ulnar side of the LI 10 (shousanli) region, at the proximal edge of the supinator muscle, which lends its name to this injury. The symptoms of supinator syndrome are similar to lateral epicondylitis with the patient complaining of lateral elbow pain. Additionally, both of these injuries are common in racket sports. However, the pain associated with supinator syndrome does not include a fixed pain site located over the common extensor tendon attachment on the lateral epicondyle. The pain of supinator syndrome is reported as worse with activity but diminishing with rest, and it is usually felt as a deep and distending pain in the region of LI 10. The pain can progress to sharp and can spread to the lateral epicondyle with increased activity, which can make a differential diagnosis with lateral epicondylitis even more difficult. Another key difference between supinator syndrome and tennis elbow is that supinator syndrome often presents with weakness of the wrist, finger and thumb extensors. The posterior interosseous nerve innervates the extensor digitorum communis, extensor indicis and extensor carpi radialis brevis, and these muscles will easily fatigue with activity as a result of the nerve entrapment.
Sports Medicine Assessment
- Lateral elbow pain with possible paresthesia into the lateral forearm along the course of the San Jiao channel
- Supinator MMT (Fig. 2) repeated 4-6 times will often create pain in the LI 9 (shanglian), LI 10 (shousanli) and/or LU 5 (chize) region and possibly extend to the lateral epicondyle
- Mill’s and Cozen’s tests for lateral epicondylitis may create a painful response, but the pain is found more in the LI 10 (shousanli) region rather than at the lateral epicondyle
- The patient may report that the forearm and hand feel weak, heavy and/or uncoordinated
- Differential diagnosis: The practitioner will need to differentiate supinator syndrome from other causes of lateral elbow pain, such as: triceps tendinopathy, anconeus strain, lateral epicondylitis and cervical radiculopathy if paresthesia is present