The body is a machine with lots of moving parts. Pulley systems within the body make many difficult tasks simpler. Your psoas muscle acts like a pulley and so do your Quadriceps muscles. Our legs are designed to track directly over the ankles when you walk and run. This is one of the main distinctions of being upright and walking on two legs.
Before we began walking on two legs the knees of our ancestors moved out to the side rather than in towards the midline of the body. This brought a lot of changes to our musculature including the development of strong pelvic muscles and the awakening of a new function for the posas major.
The quadriceps muscle is an extensor of the knee. You can feel this by standing and lifting your knee up in the air with your hand on the lifted quadriceps muscle. It won’t be doing much, but if you try and lift the foot to the height of the knee you will feel the quadriceps engage to lift the lower leg. This is actually a lot of work for one muscle but there are two key factors helping to accomplish the feat.
Our kneecap, the patella bone, is embedded into the quadriceps, on top of the knee joint, as it moves down to the lower leg. The bone within the muscle increases its mechanical advantage as does the quadriceps acting like a pulley. The quadriceps muscles attach on the leg and pelvis and moves down towards the knee on a slight angle. At the knee it runs through a groove in the tibia, the big bone of the lower leg. The top of the bone acts as the pulley and the quadriceps is the rope that helps to extend the lower leg.
Technically when your knee lifts off the ground to walk and run it should pull very slightly to the inside due to the angle of the quadriceps and the way it fits into the groove of the knee. This movement to the inside, however slight, keeps pressure off of the outer knee and allows for us to stay grounded through the inner foot.
This natural action is very often prevented due to tightness in the hips and outer thighs due to postural imbalances that throw off the alignment of the pelvis, legs and everything in the surrounding area. Knees moving out to the outside rather than to the inside factors into all aspects of our moving life and can be a main cause of chronic pain and injury.
Our poor sad quadriceps muscles are thrown into dysfunction due to numerous factors some of which we have covered already and some still to come. Freeing our quadriceps to work more to their design by improving our posture and walking patterns is a priceless gift to give to your body.