The adductors are made of 4 muscles: the adductor longus, brevis, magnus and the gracilis.
Adductor Longus & Brevis
The adductor longus is the most common cause of groin pain. Trigger points in the longus and brevis project both towards the pelvis and the knee. It may even extend down the lower leg. The adductor longus starts firing at the time of toe off during walking or running. You will probably only notice pain during vigorous exercise or muscular overload if you have trigger points in these muscles. Especially with sudden hip twists.
Trigger points in the adductor magnus are described as deep, almost as if it might even be in the pelvis. The pain may be described as shooting up into the pelvis and shooting like a firecracker. Ouch! The adductor magnus starts firing at the time of heel strike in walking and jogging and also going up stairs and holding on with your legs while riding a horse. Pain may be described as “deep inside” the pelvis and may only occur during sexual intercourse. You will have difficulty positioning the leg when sleeping. Laying on your side with a pillow between your legs will be most comfortable.
Trigger points in the gracilis cause a hot, stinging pain along the entire inside of the thigh. They are most active when jumping for a volleyball spike or basketball layup. The pain may be constant at rest and no change in position relieves it but walking tends to make the pain ease up.
How do knots get there?
Trigger points in the adductors are activated by sudden overload like slipping on the ice and resisting spreading the legs while trying to get balance. Arthritis in the hips can also activate them as well as horseback riding, skiing, or long bike ride. You will normally remember one event that happened to cause the pain. The trpts will continually be there if you do things like run up and down hills or sit for a long time in a car or chair.
How to get rid of them
To correct this problem you must avoid leaving the muscle in a shortened position. Sleep with a pillow between your knees and avoid excessive hip flexion (drawing the knees towards the chest). Avoid crossing your legs. Use cruise control on long auto trips.
So the stretches as outlined in the videos below. Doing them in a warm swimming pool will be even more helpful.