sesamoid

The patella (kneecap) is a 'sesamoid bone'. A sesamoid bone is a bone that develops in a muscle tendon, rather than being attached by ligaments to another bone. The tendon in which the patella develops is the tendon of the quadriceps muscle, the big muscle that makes up the bulk of your 'lap'.

Those were my words, when I was told I had a Fabella bone in my knee.

A Fabella bone is an extra sesamoid bone, located laterally, behind the knee. Only about 10% of the population has a Fabella bone. It is embeded at the head of the Gastrocnemius tendon. It is about the size of a pea and is very difficult to see on xray. Believe it or not, this little bone is susceptable to arthritis, fracture, dislocation and impingement.