Joint Blocks: Procedure, Benefits, and Risks

Facet joint injections are used to diagnose and/or treat spinal facet joint pain. Facet joint pain typically presents as low back pain, with or without referred pain into the leg. Studies have shown that facet joints can be damaged in accidents (e.g. motor vehicle accidents), and that changes in the facet joints may not show up on x-ray, CT scan or MRI scanning.

Facet joint injections are used in two circumstances.

  1. The first is during the more acute phase of pain, where pain doesn’t settle quickly enough with the use of such things as exercise, medication and physical therapy. In this case, the injection may also include cortisone.
  2. The second is for chronic presentations where pain is not always present. If pain can’t be reliably predicted to be present in the six hours after the injection, diagnostic nerve block is not relevant. If a facet joint injection leads to some prolonged improvement, it is likely that the facet joint is the source of pain.

Facet joint injections are only used after confident diagnosis that pain is related to the facet joint. This diagnosis is done via a medial branch block.


The major reason for the injection is to determine whether or not pain is altered in the six hours after the injection. Therefore, it’s important to have a method for recording the pain score. You will be kept in recovery for a couple of hours until the doctor or nurse determines when it is safe for you to go home.


A commonly-used pain scale rates pain from 0 to 10. When represented in a linear fashion on a chart, it’s called a Visual Analog Scale (VAS).


Zero (0/10) indicates no pain while 10/10 indicates pain that is almost unattainable. At 10/10 a person can’t think, move or function at all. Each person needs to know what their VAS is, and apply it to each area of pain. For example, your back pain may be 6/10, and leg pain is 4/10.


If so, two columns of the pain chart need to be recorded. As the aim of the block is to see if pain is altered, it’s essential that pain is present at the time of the injection. Thus, patients shouldn’t take pain medication on the day of the injection.


It’s normal to feel anxious about the injection. However, the injections are very safe, generally not too painful, and can be done quickly.The injection itself consists of placing a needle through the skin under an x-ray machine. The needle is placed directly on to bone. A thin needle (not much thicker than an acupuncture needle), is used. Other than local bruising and pain, the procedure does not have any side effects. In five per cent of cases, pain and bruising can last for a few days. Generally, only one or two facet joint levels are investigated at a time to ensure the diagnosis is specific to a level in the lumbar spine.You should be driven home after the procedure. If good relief is obtained from the injection , then it’s assumed the facet joints are the main cause of pain, and the radiofrequency neurotomy (RFN) procedure should benefit you.


If there is no relief following the first session then it may be necessary to investigate other levels, which may require two sets of injections. Your doctor will determine if other injections should be done. If there is still no relief then the conclusion is the facet joints are not the cause of the pain. As mentioned above, you must rate your pain between 0 and 10, with 0 equalling no pain, and 10 equalling worst pain imaginable. You should rate your pre-injection pain both in terms of your movements and how you feel doing the things that most aggravate the pain, and then over the next six hours, you should record your pain levels on the pain chart, at the intervals initially of half an hour, and then hourly.


You may need to describe separately different pains that you experience.


For example, you may have low back pain and leg pain, and these two pains should be described separately. For instance, the injection may totally relieve the low back pain, but may not help the leg pain. This is important information for your doctor to assess when making recommendations regarding further treatment.