The adductor muscles run down the inside of the thigh. They can become injured when over stretched or forcibly contracted such as with martial arts, or rapid changes of direction.
Typically you will feel a sudden pain along the inside of the thigh or groin. You may feel something tearing. You may feel able to carry on playing, but after cooling down the area will become stiff and painful. In more severe cases you may be unable to continue, and walk with a limp.
If you think you have this injury it is well worth getting it checked out by Mr Willis-Owen. It is important to treat this early with rest, ice, compression and elevation in order to minimise the bleeding and swelling. You should avoid any aggravating activities with may prolong the problem. It generally will get better on its own if diagnosed early and treated appropriately.
Treatment involves first confirming the diagnosis then establishing the underlying cause. Options may include activity modification, physiotherapy, anti inflammatories. Usually a carefully directed graduated physiotherapy program is all that is needed.