What is an intra articular injection?
This is a procedure during which a drug (usually local anaesthetic and steroid) is injected into a joint. This can be performed on any joint and is commonly performed on the knee and hip.
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.
As well as helping diagnose the cause of the pain, the injection can also give pain relief for a prolonged period of time.
How is it performed?
Injections into the knee can be performed in outpatient clinics as the joint is large and easily accessible.
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 the operating theatre on an outpatient basis to allow use of the mobile xray machine – an image intensifier.
Lying on the operating table, the front of the hip is cleaned with a dark brown fluid (betidine). Suitable underwear can be worn but is permanently stained by this fluid.
Local anaesthetic is injected into the skin and the needle is advanced into the hip joint being guided by the image intensifier. Once in the hip joint a special dye (omnipaque) is injected to confirm the needle is in the joint.
Following this, local anaesthetic and steroid are injected and the needle removed.
Injections should not be performed in people who have active or suspected infections in the joint or infection in the overlying skin. The steroid affects glucose control in diabetics and insulin requirements may be altered. The steroid can cause hypopigmentation of a small area of skin but this is usually temporary. Atrophy 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 and usually due to poor technique. 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.
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.
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.