Protruding muscles on the front side of the thigh in women can be the result of several reasons: First, it may be the result of exercises performed on the lower limbs. If such women often do exercises that involve lifting or straightening the knee joints of the lower limbs, like running, swimming, pedaling bicycles, etc., it can cause the quadriceps muscle to be strong and to behave in a more prominent way. Second, it may be caused by the patient standing for a long time. In the process of standing, the quadriceps muscle will continue to maintain contraction, pulling the knee joint, keeping the knee joint straight, over time, it will cause the quadriceps muscle to become strong and prominent. Third, it may be caused by the patient being too thin. Some women lose too much weight, causing the subcutaneous fat to be very thin, and when they wear shorter pants or skirts, they will see obvious muscle lines in the thigh area.