Hip & Knee Injections
What is an Intra Articular Injection?
This is a procedure during which a drug is injected into a joint. This can be performed on any joint and is commonly performed on the knee and hip.
Two different injections are commonly administered:
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Corticosteroids and local anaesthetic
“Steroids” are powerful anti-inflammatory agents. They reduced inflammation, swelling and pain. The effect of the local anaesthetic can work almost straight away, the effect ( if any) of the steroid may take a few days. It is not uncommon to have a flare of the pain when the steroid starts to act. The injection may or may not work, and if it does, typically lasts for a maximum of 3 months.
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Viscosupplementation
These injections contain HA (Hyaluronic Acid), a substance made naturally by your body. It is contained in the fluid that helps lubricate and cushion your joints and keeps them working smoothly. In osteoarthritis, the hyaluronic acid in the affected joint thins. Hyaluronic acid injections add to your body’s natural supply. The effectiveness of the injections is variable, but some studies have shown them to be more effective than steroid injections.
Hip Injections
Why is it necessary?
At times it can be difficult to determine if a patient’s pain is caused by their back or hip. The pain killing injection into the hip helps the surgeon to decide which area is causing the pain.
If after the hip injection, the pain is reduced, it can be assumed it is the hip causing the pain. If the pain is unaltered, somewhere other than the hip is probably the cause. The injection will also give a guide to how much pain relief can be expected if a hip replacement is undertaken.
These injections can also be used for people with painful hips who are not medically fit enough to have an operation, or feel their symptoms do not warrant a hip replacement.
As well as helping diagnose the cause of the pain, the injection can also give pain relief for a period of time.
How are they performed?
The hip joint is deep inside the body. Without some form of guidance (xray or ultrasound) it is impossible to know if an injection has gone into the joint or not. The procedure is undertaken in an outpatient operating room or operating theatre. A mobile x-ray machine (image intensifier) or ultrasound machine is used.
The front of the hip is cleaned, suitable underwear should be worn as it can be stained.
Local anaesthetic is injected into the skin and the needle is advanced into the hip joint being guided by a image intensifier or ultra sound machine. Once in the hip joint a special dye (omnipaque) is injected to confirm the position of the needle.
Following this, usually local anaesthetic and steroid are injected, and the needle removed.
Possible Complications
Injections should not be performed in people who have active or suspected infections in the joint or infection in the overlying skin. Steroid affects glucose control in diabetics and insulin requirements may be altered. Steroid can cause hypopigmentation of a small area of skin, but this is usually temporary. Atrophy (wasting) of fat can also occur.
There is often a sharp scratch and sting as the local anaesthetic is injected into the skin.
As the needle is advanced into the hip there may be some discomfort, but further local anaesthetic can be given.
There may be a flare of the hip pain after the injection and simple pain killers such as paracetamol or codeine based medicines can be used.
You must rest for 48 hours following the injection to allow it to have its maximum benefit.
It is possible to cause an infection in the joint, but this is rare. No accurate figures are available for the hip but in the knee, the chance of an infection occurring is between 1:300 and 1:5000 after an injection.
The local anaesthetic can leak out, affecting the function of the nerve (femoral nerve) controlling the muscles on the front of the thigh. For 4-6 hours following the injection, it is important to test these muscle by straightening the knee before standing up.
Some studies have shown an increased infection rate in patients who go on to have a total hip replacement, but this has not been shown in all research. It may be sensible to wait 2 months between having an injection and going on to have a hip replacement.
Recovery
After the injection you should rest for 48 hours. Many people like to keep a “pain diary” to record what, if any, benefits it has given.
I will usually see you in clinic 4-6 weeks afterwards to discuss the effect of the injection.
Knee Injections
Knee injections are not as difficult to undertake, as the knee joint is not surrounded by a deep layer of muscle. Imaging with xray or ultrasound is not therefore needed, and the procedure can be undertaken in the outpatient setting.
How are they performed?
The front of the knee is cleaned with an antiseptic solution. Preferably you should wear a skirt or loose fitting trousers so the knee can be easily exposed.
The substance (steroid or viscosupplementation) is injected directly into the knee. The needle is withdrawn and a plaster applied.
Possible Complications
Injections should not be performed in people who have active or suspected infections in the joint or infection in the overlying skin. Steroid affects glucose control in diabetics and insulin requirements may be altered. Steroid can cause hypopigmentation of a small area of skin, but this is usually temporary. Atrophy (wasting) of fat can also occur.
There is a sharp scratch as the needle is inserted.
There may be a flare pain after the injection and simple pain killers, such as paracetamol or codeine based medicines can be used.
You must rest for 48 hours following the injection to allow it to have its maximum benefit.
It is possible to cause an infection in the joint, but this is rare. The chance of an infection occurring is between 1:300 and 1:5000 after an injection.
Recovery
After the injection you should rest for 48 hours. Many people like to keep a “pain diary” to record what, if any, benefits it has given.
I will usually see you in clinic 4-6 weeks afterwards to discuss the effect of the injection.