Ultrasound is high frequency sound waves produced by a special machine. They can penetrate the skin providing very useful images of the deep tissues within the body. Cortisone is an anti-inflammatory medicine that can help relieve pain and inflammation.  It can be injected into a joint to help relieve pain, usually in the context of arthritis. This is referred to as "an intra articular cortisone injection". It is also used to treat other inflammatory conditions like bursitis (inflammation of sac like fluid collections present in different parts of the body) and tendonitis (tendon inflammation). There is a significant evidence that ultrasound guided injections provide better levels of pain relief and longer effects compared with injections done without imaging guidance.