A groin strain occurs when the muscles of the inner thighs are stretched beyond their normal length. This results in tears within the muscle that cause pain and inflammation. The groin muscles are medically known as the adductors muscles. The adductors are comprised of five muscles; the adductor magnus, longus, brevis, pectineus, and gracilis. When these muslces contract, they bring the leg to midline. Overstretching these muscles results in a groin strain.