Can psoas muscle cause entire leg pain that starts at the top of the leg and goes down the leg/thigh and down to the foot ?

Rarely: Some of the nerves to and from the legs pass through the muscle. If the muscle has an abscess (pus collection) or tumor (pretty rare), it might irritate those nerves, but both of these scenarios is quite rare. If the pain is not improving, see your primary doctor or your back doctor (if you have one).

Not usually: The iliopsoas muscle runs from inside your pelvis and crosses your hip joint and attaches to the femur. Its chief function is to flex the hip/leg. Pains related to psoas problems are usually restricted to the hip and upper leg and rarely go south of the knee. There is a possibility that this pain is related to a nerve problem and should have it evaluated.