The extensor mechanism consists of the anatomical structures which work together to straighten the knee.

This chain of structures reaches from hip bone to tibia bone and contraction of the muscle/tendon unit straightens (extends) the knee. Chief of these is the quadriceps muscle group.

The patella plays a key role in this process by altering the 'lever arm' and thus the mechanical forces involved.


An explanation of factors affecting measurement of the Q-angle.

The patella - important anatomical relationships

The kneecap or patella is part of a chain of structures that help to straighten the knee.