Stance Variables Affecting Knee Health
Whenever you squat, hack squat, or leg press, your foot position is an important variable in determining not only the results you'll obtain from the exercise, but also the safety of your knee joints. Although each individual must determine their own best stance exercise per exercise (based on their own anatomical peculiarities such as height and leg length), the following variables must be taken into consideration:
The quadriceps muscles can contract more efficiently when the feet are pointing slightly outward. They should NEVER point straight ahead. If you squat with a very wide stance, your adductors tend to assist the quads. This can result in stress to the medial collateral ligament, abnormal cartilage loading, and improper patellar tracking.
During the descent phase of any type of squat, do not allow the knees to extend beyond your feet. The further your knees travel over your feet, the greater the shearing forces on the patellar tendon and ligament.
Make sure that your knees point in the same direction your feet are pointing during the descent and ascent. Because of weak quads, many lifters inadvertently turn their knees inward during the ascent, placing great stress on the medial ligaments of the knee.
Although many top bodybuilders advocate a very close stance for the purpose of isolating the outer quads, this is a myth, and it places you at risk, particularly since you'll have to use a lot of back to execute the lift, or (if you use heels) place great shear and compression on the knees. The best way to squat is to put your feet in a position where they can generate the greatest opposing force to the weight ("the athletic postition").
Warm up thoroughly before squatting. Your muscles and other tissues of the knee joint LOVE warmth! Remember the analogy, cold taffy breaks, warm taffy doesn't.
Maintain reasonable flexibility in the joints of your lower extremities and back. Many knee injuries can be traced back to poor position resulting from inflexibility.
Finally, be very careful in the exit out of the rack, and getting "set" in the squat stance. After lifting the weight off of the pins, you should take just one step backward and immediately assume your squatting stance. This takes time to master, but eventually all the minute adjustments can be pared down substantially.
Once set in the stance, keep your feet "nailed down" for the duration of the set. Many people "fidget" with their feet and toes between reps which can cause a variety of problems ranging from a break in concentration to a loss of balance - and attendant stress on your knees.
Link:
http://www.bodybuilding.com/fun/drsquat12.htm
http://optimumsportsperformance.com/blog/?p=624
