How safe are arthritis jabs for dogs and cats? 

Arthritis jabs have come under fire recently, with concerns raised about potential side effects. These medications are relatively new compared to some other arthritis medications, which is probably why they are under scrutiny. Since their release in the UK nearly five years ago, they have proven to be extremely popular, being regularly used by veterinary practices across the country. But does this mean they are safe? 

We’re going to pick apart the fact from the fiction to help you make an informed decision about your pet’s medical care. 

What is arthritis, and how does it affect my pet? 

First things first, let’s look at why you might treat your pet with ‘arthritis jabs’ in the first place. 

What causes arthritis? 

There are different types of arthritis, but the most common for cats and dogs is osteoarthritis. This is a progressive joint condition that can occur secondary to a joint abnormality (e.g. hip dysplasia) or a previous injury. However, in many cases, there is no identifiable cause. Ageing and general ‘wear and tear’ are well-known risk factors for osteoarthritis. This condition is therefore commonly found in older or overweight animals, as well as in large and giant dog breeds. Certain breeds also seem more at risk than others, so there may be a genetic factor at play, too. 

In healthy joints, cartilage is found at the ends of your pet’s bones. This cushions the joints and allows them to move smoothly and without friction. In osteoarthritis, the cartilage doesn’t function properly, and it becomes eroded. Gradual loss of cartilage tissue occurs along with other changes, such as uncomfortable thickening of the joint capsule and new bone formation (osteophytosis). This contributes to pain and inflammation. Your pet’s joints become stiffer and more uncomfortable. This is a progressive condition, so it will continue to get worse over time. 

What are the signs of arthritis? 

Signs of arthritis in cats and dogs include one or more of the following – 

How is arthritis diagnosed? 

Your vet will begin by examining your cat or dog. They will also discuss their symptoms with you to understand your pet’s mobility and pain at home. 

Depending on their findings, they may suggest diagnostic imaging, with X-rays (radiography) or computed tomography (CT) being the most useful tools. Imaging can help to determine the severity of the problem but may also help to decide whether surgical intervention or medical/conservative care is best for your pet. 

Diagnostic imaging is not always performed, however, and sometimes it is more appropriate to suggest a pain relief trial and assess your pet’s response. This is especially true in older patients, with general wear and tear being a likely cause for their joint issues. 

What are ‘arthritis jabs’ and how do they work? 

Some owners refer to the monoclonal antibody injections used in the treatment of osteoarthritis as ‘arthritis jabs’. The injections contain a type of anti-nerve growth factor antibody specific to the species it is treating; for cats, this is frunevetmab, and in dogs, this is bedinvetmab. Your vet may refer to these under their trade names. 

These synthetic antibodies act like the ones found naturally in the body. The role of antibodies is to target specific molecules involved in certain disease processes. The antibodies in these injections target nerve growth factor (NGF), which is elevated in some chronic, painful conditions such as osteoarthritis. NGF binds to receptors on neuron and immune cells, increasing pain. They also trigger the release of chemicals that promote inflammation, causing the release of even more NGF.  

The antibodies in arthritis jabs stop NGF from attaching to nerve receptors. This interrupts the transmission of pain signals and reduces inflammation. 

Because the active ingredient of these injections is antibodies (which are made of protein), these can be readily processed and excreted via the normal pathways in the body that exist for handling proteins. This is good because it doesn’t put any excess strain on the liver and kidneys, which can be particularly helpful for pets that need long-term medication for joint disease. 

These injections need to be administered by a veterinary professional every 4 weeks to be effective. The injection is given subcutaneously, in the same way that a vaccination would be performed. 

How safe are ‘arthritis jabs’? 

Any medication that we give to our pets (or indeed take ourselves!) has the potential for side effects. There is always a risk, benefit analysis that needs to be considered any time we medically intervene. 

What are the listed side effects of these injections? 

Frunevetmab and bedinvetmab have both performed well on safety in clinical trials. Side effects are more common in cats than in dogs, though, with some cats experiencing a localised skin reaction after injection. Side effects for dogs appear to be uncommon or rare. There are also no known interactions with other drugs, including antibiotics, parasite treatments, and vaccinations. The data sheets that accompany these medications list the following side effects in their clinical particulars – 

Bedinvetmab (for dogs) 

Frunevetmab (for cats) 

Well, that all sounds good so far – what’s the problem then? 

Concerns have been raised about side effects not currently listed in either drug’s data sheets. The focus is on musculoskeletal and neurological side effects, including increasing lameness, neurological episodes, and urinary issues. In the human equivalent medication, issues were reported about accelerated joint degeneration in humans, possibly due to the way NGF helps regulate bone and cartilage turnover. There are concerns about the same side effects being true in our pets. 

However, it can be very difficult to determine if there is a true side effect of the medication occurring or whether it is due to a deterioration of the disease that is being treated for. Quite a few cats and dogs have advanced osteoarthritis by the time arthritis jabs are started, and we know that the disease is progressive and will get worse over time. 

Social media has taken some of this and run with it 

Campaigns are continually springing up from non-experts against new drugs (including monoclonal antibody injections), which are largely unfounded or based solely on anecdotes. This type of scaremongering around modern medicine could endanger the lives or welfare of pets, particularly evident in the recent upsurge in anti-vaccination. So, what does the science say about arthritis jabs? 

In a paper published in April 2025, no surprises were reported. They stated that the majority of adverse events reported were all in line with the expected ones listed in the product’s data sheets. The paper states ‘Within musculoskeletal adverse event reports, none of the reviewed reports met the criteria for RPOA as described in humans.’ (RPOA = Rapidly progressive osteoarthritis). This suggests that the same issue is not occurring in dogs as it does in people – or at least, if it is, that it is either very rare, or not being reported. Reported musculoskeletal side effects could be due to the natural progression of existing osteoarthritis or an unrelated event like immune-mediated conditions, joint overuse or rarely a humeral condylar fracture. Many of the cases lack sufficient information, including pre and post treatment radiographs and reports on patient activity levels, body condition score, and previous diseases affecting the involved joint/s. Having more accurate patient information would allow for better pharmacovigilance. 

However, a paper published just a month later in May 2025 stated the opposite. It did seem to suggest there is a link between dogs treated with bedinvetmab and an increased number of ligament/tendon injuries, polyarthritis, fractures, musculoskeletal neoplasia, and septic arthritis reports, compared to other arthritis medications. In the paper’s discussion, they said ‘Furthermore, independent expert review of a subset of cases strongly supported a causal association between Librela and accelerated joint destruction’. The paper also suggests that bedinvetmab had limited pre-clinical trials and didn’t screen patients for accelerated joint destruction using radiographs. This could explain why these are currently not listed as potential side effects, and instead, we are reliant on ‘post-marketing surveillance’ instead – meaning these things might only coming to light now that the drug is on the open market.   

So… just how safe are arthritis jabs for cats and dogs? 

It is important to keep things in perspective. These injections have proved to be extremely popular and effective, improving the quality of life of thousands of cats and dogs. While adverse events are worrying, they still seem to be rare currently. More accurate research and reporting of cases is needed to build a better picture. 

Vets and drugs manufacturers take adverse reactions seriously, and there is a reporting system in place. The Veterinary Medicines Directorate (VMD) has some useful information about how owners and vets can report adverse events, helping with pharmacovigilance and product safety. 

You should discuss any concerns you have with your vet, who will be happy to explore all of the various osteoarthritis treatment options with you. You might decide that arthritis jabs definitely are the right answer for your pet, but in some cases, there is an alternative that suits better. 

Summary 

Most medicines have a list of possible side effects that are discovered during safety trials, but sometimes new ones emerge when a drug reaches the general public. At present, more research is needed to accurately say whether there is a link between arthritis jabs and an increased risk of accelerated joint destruction or other musculoskeletal issues. 

What we can say however, is that arthritis jabs have improved the lives of thousands of pets and they are great option for many animals. If you have any questions about your pet’s arthritis treatment, then don’t hesitate to raise them with your vet.