Anconeus Epitrochlearis Muscle

The anconeus epitrochlearis (or accessory anconeus) muscle is thought to represent an atavistic muscle that is usually found as a remnant (epitrochleoanconeus ligament). It can be found intact in ~5% to ~35% of cadavers. A recent MRI study found this muscle in about 25% of patients.

The image above shows anconeus epitrochlearis muscles in 4 different patients. While the anconeus epitrochlearis muscle (white arrows) can cause cubital tunnel syndrome by compression of the ulnar nerve (pink arrows), it is commonly found in asymptomatic elbows.

References

• Husarik DB, Saupe N, Pfirrmann CW, Jost B, Hodler J, Zanetti M. Elbow nerves: MR findings in 60 asymptomatic subjects--normal anatomy, variants, and pitfalls. Radiology. 2009 Jul;252(1):148-56.
• Jeon IH, Fairbairn KJ, Neumann L, Wallace WA. MR imaging of edematous anconeus epitrochlearis: another cause of medial elbow pain? Skeletal Radiol. 2005 Feb;34(2):103-7.