Presentation
Lateral elbow pain
Patient Data
Transverse ultrasound image at the cubital tunnel, with the elbow in flexion position.
An accessory muscle belly (A) is seen superficially in the cubital tunnel, consistent with the anconeus epitrochlearis muscle. The ulnar nerve is also seen (U). The patient also had a lateral epicondilitis (not shown) and had no pain at the medial elbow. This suggests the fact that the muscle is an incidental finding.
Both structures appear hypoechoic due to anisotropy.
Case Discussion
Accessory muscles are relatively common findings in musculoskeletal exams. Most of them are asymptomatic, but occasionally, because of the mass effect, they can cause compressive neuropathies. Accessory muscles also may cause a palpable mass, as an example the accessory soleus muscle in the ankle.
The anconeus epitrochlearis muscle is usually asymptomatic, but may be the cause of ulnar neuropathy in some patients.
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