Movements of the knee

The knee is primarily a hinge joint. Movements of this joint include;

Flexion; ROM for flexion is dependant of whether the knee is in active flexion or passive flexion.

• Active flexion; such as standing and bending the knee to bring your foot behind you. The degree of flexion is limited by contact between the bodies of the contracting muscles (the hamstrings and the calf)
• Passive flexion; such as kneeling with your heels touching your bottom. In this position, the degree of ROM is increased because the muscles are passively stretched and compressed. This means that the muscles are in a relaxed state and are not working to maintain the position of the legs.
• ROM of the knee in flexion is also affected by the position of the hip. When the hip joint is in extension (lifted behind in an arabesque) the rectus femoris is lengthened. As this muscles crosses both the hip and the knee, it's extended position inhibits knee flexion. The opposite is true of hip flexion. In this position, the rectus femoris is shortened, therefore allowing for more knee flexion.

Extension; this is returning to the anatomical position from flexion. ROM of the knee when moving it from flexion into extension, is greater when the hip is in extension. When the hip is in flexion (lifting your knee up towards your chest), the degree of extension is inhibited by the length of the hamstrings.

Imagine you have put your leg up on a ballet barre or other high surface to stretch the hamstrings. You may not be able to straighten your knee if the hamstrings are tight.

Hyperextension; (or genu recurvatum) this is not an actual movement of the knee but a deviation from the normal anatomical position. Hyperextended knees are caused by longer than usual ligaments in the knee and causes the angle of the knee to go beyond 180 degrees.

Hyperextended knees are common in dancers who are usually more flexible than non dancers and is often a desirable atheistic. However, knees such as these can be less stable and can cause other postural issues. This can be a domino effect; the pelvis often has to move forward in compensation, followed by the ribcage and then the head. See the video below for more information about hyperextended knees in relation to posture.

Lateral rotation; this is when the tibial tuberosity moves laterally. i.e. the knee twists outwards.

Medial rotation; the tibial tuberosity moves medially. i.e. the knees twist inwards.

These two movements are very small and occur only when the knee is bent in flexion. When the leg is straight, the appearance of lateral or medial rotation is actually occurring at the hip.