The patella (knee cap) is the largest sesamoid bone (a bone formed within the tendon of a muscle) in the body and is formed within the tendon of the quadriceps femoris muscle as it crosses anterior to the knee joint to insert on the tibia.
The patella is triangular:
Its apex is pointed inferiorly for attachment to the patellar ligament, which connects the patella to the tibia (Fig. 6.54).