• edwardbusuttil

Joint Medication: Part 3 - Commonly used joint medications



OK - Just putting this out there at the beginning of this post, this is a long read. I wanted to provide an all encompassing guide to the routinely available options for joint injections. Injections into joints are routinely called intra-articular injections. Although your choice might be driven by what is financially viable, insurance policy or availability of certain medications and services in your area, knowledge is power.


Scientific data is constantly evolving. Things change, and as a result, when new, additional or contradictory information is available, I will try to update the blog. Equally, if someone knows of a scientific study which would add to the blog, please send it my way.


A lot of the studies involved in this blog post are based on injection into a single type of joint. The medication may work better, or worse, in another joint. None of the studies involved provided the owners with regimented rehabilitation plans based on which area was being injected. This MUST have a huge influence on the success of the medication. This is why I call joint injections LIQUID PLASTERS. I truly believe that hard work before and after joint injections significantly improves the outcome.


This also influences the most frequently asked question associated with joint injections: ‘How long will the medication last for? Will I have to repeat it again?’

Nobody can ever give you an accurate time frame. It depends on the severity of the lesions, and again, the work which you are prepared to put in. Working with someone that truly understands the biomechanics of your horse’s joints can really help to get you on the right track.


Every case is specific, and my preferred treatment would be based on a multitude of factors discussed during consultations. This guide in mainly to help you understand how the treatment is supposed to help your horse.


 

The risk associated with every type of joint injection - flare and sepsis (joint infection)


Unfortunately, an occasional risk of joint injections involves reactions to the procedure and medication injected. This may be a:

  • Flare up - non infectious process and generally resolves with pain relief, more commonly after injection of hyaluronic acid (1).

  • Sepsis - infectious disease due to introduction of bacteria or fungi into the joint (1). May require surgery to remove the infection.

Can risk of sepsis be decreased?

A sterile scrub should be performed before any joint is injected. A 2021 study (2) showed that the frequency of sepsis is about 0.04%, with no difference between joint injections performed in the field or in hospital settings, or when antibiotics were combined with the medication.

The most commonly used antibiotic is amikacin, however, it has recently been found to cause joint damage as well (3).


 

Steroids

The body naturally produces corticosteroids. Corticosteroids are strong anti-inflammatories, decreasing inflammation both in the short and long term. Although the short term change is pretty obvious, long term change is achieved through gene regulation (4). This basically means that the increased load of steroids affects the body to subsequently produce more anti-inflammatories. Therefore, decreased inflammation is due to the steroids injected and their effect on the rest of the body.


The two main steroids used are called Triamcinolone (TA) and Methylprednisolone Acetate (MPA).

  • TA is detected within the joint for just 10 days after administration, and is almost undetectable in the blood after 48 hours (4).

  • MPA gets broken down to methylprednisolone (MP) within the joint, and remains detectable within the joint for 5-39 days. Although MPA is not detected in the blood, MP can be detected for 1-30 days (4).


What does this mean?

The FEI outlines the importance of anti-doping to promote a clean and fair sport. Because of how long TA and MP last in the blood for, the withdrawal period (time between injection and when a horse can compete) is 7 days for TA and 28 days for MPA.

A full list of detection times can be found here: https://inside.fei.org/system/files/FEI%20Detection%20Times%202018_0.pdf


Do they have any negative effects?

  1. In the joint, MPA has negative effects on articular cartilage (5). This does not appear to be the case with TA (6).

  2. Laminitis - scientific evidence shows that appropriate TA dosage administered into a joint does not increase the risk of laminitis in healthy horses (7). I have not been able to find a paper regarding MPA or use of intra-articular steroids in horses with hormonal diseases, such as Cushing’s or Equine Metabolic Syndrome (EMS).


Any other positive effects?

Intra-articular administration of TA (8) and MPA (9) also improve lung function in horses with severe asthma, and this lasts longer with TA. No vet would ever advocate using intra-articular steroids to treat asthma.


Which steroids are generally injected into which joints?

Due to the degenerative side effects of MPA, it is usually injected into smaller joints, like the tarsometatarsal joint, to promote ankylosis (fusion), therefore decreasing pain.


After the 2nd blog about joint communication, do we need to treat every joint compartment?