Lotus Position or Padmasana is one of the most historic yoga postures in the ancient tradition. However, for many Western students of yoga who spent their entire life sitting in chairs it is also one of the hardest. If you don't know the proper technique or if you rush the process you could risk injury and discomfort.
When working on Padmasana, the key is to learn how to open and rotate the hip joints. If the main bend of the posture happens through an external rotation of the hip joints then your body will learn the movement mechanic easily without injury over time. But if you just pull and crank your legs into this folded lotus position you might find yourself experiencing pain that would be avoidable with a little surrender and good technique. In order to externally rotate your hip joints you have to relax the muscles, tendons and ligaments that are closest to the head of the thigh bone. Sometimes the source of tension around the hip joints comes from a weak inner core, so be sure to keep the pelvic floor engaged.
When attempting Padmasana for the first time I recommend starting out with both legs straight. Then bend your knee and draw the heel of the right foot into the inner thigh of the left. Keeping the knee joint closed lift the ankle and the knee in unison by holding equally under both with your hands. Gently lift the instep of the right foot onto the left hip crease and encourage a slightly deeper external rotation of the right hip joint. Next bend the left knee along the center line until the left foot is under the right shin. Then bring the left knee slightly out to the side while keeping the knee joint closed. Gently lift the left foot towards the right hip crease. Keep your knees soft and do not squeeze your legs. Allow your hips to open and breathe fully.