Arthritis is a general term that refers to any kind of joint disorder. According to the Centers for Disease Control and Prevention, there are over 100 different types of arthritis, all of which share the similar symptoms of joint pain and stiffness.
The most common types of arthritis are osteoarthritis and rheumatoid arthritis. There’s no cure for osteoarthritis, and while remission is the goal with rheumatoid arthritis, this is rarely achieved. Given these outcomes, managing symptoms like pain and inflammation are key to maintaining quality of life.
Medications used to manage osteoarthritis and rheumatoid arthritis include nonsteroidal anti-inflammatory drugs (NSAIDs) and sometimes opioids for pain. Other pharmaceuticals may also be prescribed depending on the type of arthritis involved. However, in many instances, management strategies come up short; medications can have detrimental side effects; and sometimes, patients simply want more options to manage their pain.
This is where cannabis and its anti-inflammatory properties come into the picture. At this point, it’s pretty widely acknowledged that cannabis can help with many different types of pain. Anecdotal evidence gathered from multiple sources—a survey in the UK, another in Australia and one conducted by HelloMD with UC Berkeley—support the idea of using cannabis to manage pain from myriad conditions, including arthritis.
Though few clinical trials exist on arthritis of any kind, emerging evidence from preclinical research suggests that the endocannabinoid system is involved. By targeting this system with compounds from cannabis, scientists hope to one day create medicines to address inflammation and pain arising from both osteoarthritis and rheumatoid arthritis.
While both osteoarthritis and rheumatoid arthritis involve inflammation of the joints that lead to pain, the reasons for these symptoms are different.
Joints—the non-cannabis kind—are the places in the body where two bones meet. In osteoarthritis, the cartilage—a flexible connective tissue that covers the ends of bones—gradually wears away as we age. As this material breaks down, less of it is available to cushion the area where the two bones meet, leading to pain during movement. As the disease progresses, nerve damage can also occur.
Typical osteoarthritis symptoms are deep, aching pains and stiffness, especially in the morning or after resting. Osteoarthritis is often the result of aging, but injuries or being overweight can also cause undue stress on the joints, leading to cartilage degeneration. Osteoarthritis is most common in joints that bear weight like the knees, hips, spine and feet.
Rheumatoid arthritis, in contrast, is an autoimmune disease. The immune system attacks the joints, leading to inflammation and swelling of the joint linings, also called the synovia.
If left untreated, rheumatoid arthritis can lead to severe joint damage. Like many autoimmune diseases, we aren’t sure what causes rheumatoid arthritis. However, researchers think that genetics, environmental factors and possible infectious exposures play a role.
Inside all of us is a network of receptors called the endocannabinoid system (ECS). This system has receptors that are located throughout the body: in your brain, your gut, even your immune cells. Due to the prevalence of ECS receptors, scientists now think that the ECS plays a key role in essential life processes like eating, sleeping and reproducing.
The main receptors in the ECS are CB1, CB2 and TRPV1. Your body also makes endocannabinoids: anandamide (AEA) and 2-arachidonoylglycerol (2-AG), molecules that attach to these receptors to produce certain effects such as pain relief. Likewise, cannabis makes phytocannabinoids, like tetrahydrocannabinol (THC) and cannabidiol (CBD) that can also attach to, or influence, these receptors.
The ECS plays a role in our immune process and how our bodies register pain. In patients with osteoarthritis and rheumatoid arthritis, that system is altered. A study published in Arthritis Research & Therapy looked at the joint fluid of both osteoarthritis and rheumatoid arthritis patients. Researchers found that both CB1 and CB2 receptors were present in the patients’ joint linings. They also discovered that AEA and 2-AG were present in the joint fluid of both types of arthritis patients, and not present in the fluid of healthy volunteers.
The presence in the joint fluid of both endocannabinoid receptors and the substances that attach to them have made scientists speculate that manipulation of the ECS can lead to therapies that can address both osteoarthritis and rheumatoid arthritis.
For now, the only published research on osteoarthritis and cannabis has been done in animal models.
One study looked at the effect of CBD on rats with osteoarthritis. The researchers injected the cannabinoid at the arthritis site and found that CBD was able to stop pain sensations. They also noted that CBD prevented the development of further pain and nerve damage.
Another study looked at the effect of CBD applied transdermally on rats with osteoarthritis. Researchers found this method of administration to be effective: The rats had reduced joint swelling and pain.
Research on osteoarthritis and cannabis continues, with a human clinical trial set to be completed in December 2018.
The endocannabinoid system’s deep involvement in the body’s immune response has led researchers to speculate that this system can be targeted to alleviate rheumatoid arthritis symptoms.
There’s specific interest in the CB2 receptor, which is abundant in immune cells. Activating the CB2 receptor may relieve rheumatoid arthritis symptoms by controlling the body’s inflammatory response. Targeting these receptors may have widespread applications for other diseases, including osteoarthritis, endometriosis and Parkinson’s disease.
A 2014 study found that humans with rheumatoid arthritis had a higher prevalence of CB2 receptors in their joint tissues than those with osteoarthritis. Researchers also showed that activating this receptor leads to less joint inflammation and bone deterioration in mice models of this disease.
There’s a good chance cannabis’s components can target CB2, though more research is needed. THC sometimes binds to this receptor, though it often doesn’t. We still aren’t clear on how CBD influences CB2, but we know that the terpene beta-caryophyllene, which is found in cannabis and other plants, can activate this receptor.
To date, only one clinical trial has been conducted on the effects of cannabis-based medicines in rheumatoid arthritis. In this double-blind, randomized, placebo-controlled study funded by GW Pharmaceuticals, patients were given an oral spray of THC and CBD in a 1:1 ratio for five weeks.
Ultimately, the researchers found significant pain reduction and improvement of other rheumatoid arthritis symptoms like morning stiffness, in patients using the cannabis-based medicine. The researchers called their results “encouraging” and emphasized the need for more studies of this nature.
As the U.S. population ages, incidences of arthritis—especially osteoarthritis—will rise. Current methods of managing arthritis have their shortcomings and in many cases only provide minimal relief. Cannabis’s ability to affect the endocannabinoid system and promising results in both clinical and preclinical research means that cannabis-based medicines to treat arthritis will likely be in our future.
Photo credit: Kristina Tripkovic