The cyamella is a sesamoid bone in the popliteus origin tendon that occurs in only a few humans and is considered to be extinct in humans. It is regularly found in many animals such as primates, cats and dogs. Its occurrence is given by Berthaume in 2021 as 0.57-1.8%. There appears to be as little correlation between its occurrence and age, sex or body size as there is with the occurrence of a fabella.
It is divided into the following types according to exact localisation:
- Popliteal sulcus
- Condylus lateralis tibiae
- Caput fibularis
It is usually discovered as an incidental finding and is asymptomatic for the rest of the patient’s life, but it can also become inflamed with prolonged heavy strain. A snapping or locking of the knee joint has also been described with a large cyamella.
Sesamoiditis or tendinitis caused by the cyamella can be treated conservatively with anti-inflammatory drugs, mechanical effects are usually treated surgically. Due to its location, it can be clinically confused with damage to the posterior horn of the lateral meniscus.