A pulled groin occurs when the adductor muscles of the inner thigh are stretched beyond their limits. This stretching can result in small muscle tears that cause pain/swelling. In severe cases, these muscles can be completely torn or ruptured. The adductors are muscles in the upper thigh that run for the pelvis to the femur. They pull the legs together when they contract, and also help to stabilize the hip joint. Proper warm up and stretching is the key to prevention.
Treatment: Groin pulls should be treated following the R.I.C.E. regimen. Avoid potentially aggravating activity for 1-2 weeks following the injury, and once you resume activity, ice the affected region following exercise to reduce swelling. Anti-inflammatory medications can be used to reduce pain and inflammation for up to a week following the injury. Once inflammation subsides, begin a stretching program followed by a low-intensity strengthening program.
Pulled groins can best be avoided via proper stretching/warm ups, as well as post-workout stretching. In the case of a severe injury, seek the opinion of a trained medical professional.