Extension means 'straightening'.

When the knee is straight it is said to be extended. A normal range of motion at the knee includes flexion, extension and a small amount of hyperextension.

-

The patella - important anatomical relationships

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

Range-of-motion is a key concept in knee rehabilitation. This paper discusses how it is measured.

Full arc extensions

Full arc extensions are early exercises to strengthen the quadriceps muscle - this article offers a video and photos to explain the exercise.

Assisted passive extensions

Exercise to increase range of movement.

Short arc extensions

An explanation of how to perform the exercise of short arc extensions, with video.

-