This information is for people who have osteoarthritis. It tells you about injections into the hip joint, a treatment used for osteoarthritis. It is based on the best and most up-to-date research.
Do they work?
We don't know. Not much good research has been done on injecting drugs into the hip joint to reduce pain and stiffness. Studies do show injections can help with osteoarthritis of the knee.
What are they?
These treatments involve injecting a drug into your hip joint. Before doing this, your doctor may draw some fluid out of the joint. This is known as aspiration of the joint. Your joints normally have fluid in them to help the bones slide smoothly over each other. If you have osteoarthritis, you may get too much fluid, which can make your joint feel tight and uncomfortable. So, removing some of the fluid may be helpful.
The two most common drugs injected into the joint are:
Corticosteroids (usually referred to as steroids). Examples include dexamethasone and triamcinolone. These steroids are similar to chemicals your body makes naturally. They're not the anabolic steroids used by some bodybuilders
Drugs based on hyaluronic acid, a chemical that occurs naturally within the joint. Brand names for hyaluronic acid include Hyalgan and Synvisc.
The National Institute for Health and Clinical Excellence (NICE), the government body that decides which treatments should be available on the NHS, doesn't recommend using hyaluronic acid as a treatment for osteoarthritis. 
How can they help?
There's not much research about injecting steroids into the hip joint. But one study shows it may reduce pain by about a half, and the results may last up to three months.  Another study found that most people who had a steroid injection had improved pain and movement after one week, and the improvements lasted over eight weeks. 
Two small studies suggested hyaluronic acid doesn't work any better than a dummy treatment (placebo).  
How do they work?
Steroids reduce inflammation (redness and swelling) by stopping the body producing certain chemicals. These chemicals are produced in response to the damage that's being done to your joint by osteoarthritis, but they actually make things worse. By putting steroids directly into the joint, it is hoped that the swelling of osteoarthritis will be reduced.
Hyaluronic acid is one of the main ingredients of the fluid found in joints (synovial fluid), and it is thought to help in shock absorption and in lubricating the joint. Hyaluronic acid is found to decrease in older people and in people with osteoarthritis. The aim of this treatment is to replace the missing hyaluronic acid in the synovial fluid.
Can they be harmful?
There's no evidence that these treatments cause any serious harm. There's a risk that injecting into a joint could lead to an infection, but this seems unlikely.