The knee is comprised of 3 bones Ã¢â‚¬â€œ the femur (the thigh bone), the tibia (the shin bone), and the patella (the knee cap) and a little bit of cartilage (the meniscus). Since it is an area where bones meet, it is classified as a joint, with its primary motions being flexion and extension (to bring the heel toward and away from the bum). Being a joint, it functions best when it is stable.Stability in the knee is created by both ligaments and muscle. For the knee, the important ligaments are the medial and lateral collateral ligaments and the anterior and posterior cruciate ligaments.
Muscular support comes from several groups of muscles that originate from 3 locations – above the hip joint, from the entire femur shaft, and from just above the knee joint. Primary support is provided by the following five muscles: on the front side – the quadriceps which extends the leg at the knee; and on the back side, all of which flex the leg at the knee – the hamstrings; the popliteus; the plantaris; and the gastrocnemius (IÃ¢â‚¬â„¢d scan all of these muscles in; however, it would make the document too big for yahoo/hotmail accounts. If you have an anatomy book, crack it open while you read).The knee joint primarily allows flexion and extension and some rotation – some rotation, but not much. When compared with the hip joint, you can see why. The hip joint looks like a ball rotating in a socket, enabling us to move into asanas where we need the femur to rotate Ã¢â‚¬â€œ like in Padmasana (lotus) and Kapotasana (pigeon). The knee doesnÃ¢â‚¬â„¢t look like it would provide that same type of rotation Ã¢â‚¬â€œ and it doesnÃ¢â‚¬â„¢t. Although sometimes, as yogis, we try to make it so.
How the knee gets injured in Yoga:
The knee is most vulnerable to injury in asana where the hip joint is intended to rotate, but for reasons of tightness, it just doesnÃ¢â‚¬â„¢t. Think Padmasana Ã¢â‚¬â€œ we want to get the ankle joint up into the groin of the opposite leg, but if the hip is tight and wonÃ¢â‚¬â„¢t rotate, the tendency can be to compensate and to rotate a bit at the knee to get the ankle in the position. One time is okay, but if your tendency is to do that each time you move into Padmasana (and other asanas that rely on this type of leg position) you will over time increase the likelihood of weakening and/or injuring your knee.