I will assume that by "shoulder calcification" the questioner is asking about rotator cuff calcific tendonopathy, or rather a calcium deposit within the rotator cuff tendon. This can be a very painful condition of the shoulder that can come on fairly quickly, sometimes over the course of a few days. The cause of it is unknown at this point, but it is definitely not related to trauma or degeneration of the rotator cuff tendons themselves. Without treatment, it usually goes away on its own, however it can take a long time. In one study, 70% of patients had resolution of the calcium deposit after 4 years.
There are several other treatments available besides waiting it out. One such treatment involves performing needle lavage and aspiration. This is best done under ultrasound guidance, and we have had great success with this treatment. It is done under local anesthesia, which means we simply inject lidocaine ("numbing medicine") in the overlying skin and around the calcium deposit. We then use a needle and syringe to inject saline (salt water) into the deposit and then draw out the loosened calcium. Typically there is significant relief of the shoulder pain within a few days, and the deposit is usually gone within a month.
Another option would be to remove the calcification through arthroscopic surgery. This has also been shown to be quite effective, although it is a bit more invasive and may involve general anesthesia.
If you are found to have calcium in your rotator cuff tendon, ask to be referred to your friendly local sports medicine specialist, especially one who uses ultrasound. We would be happy to help you out!