Can Cannabis Help Osteoarthritis?
Osteoarthritis (OA) is the number one cause of disability in older adults, leading not only to pain and reduced mobility, but to a host of other medical conditions, including increased anxiety and depression and poor quality of life. Managing OA symptoms is also a common reason many patients turn to medical cannabis. Until now, there has not been a clinical trial demonstrating efficacy of cannabis in the treatment of OA, however, studies highlighting the role of the endocannabinoid system, both in OA pathophysiology and as a possible therapeutic target for future OA drugs, suggest cannabis as an approved treatment for osteoarthritis may be closer than many think. Furthermore, cannabis has become an accepted, safe alternative for those suffering from chronic pain, which is a defining feature in osteoarthritis.
The Endocannabinoid System
Evidence highlighting an intimate relationship between the body’s endocannabinoid system (ECS) in the development of osteoarthritis and its role as a potential therapeutic target has opened up a new area of possibility for scientists researching OA drugs.
The endocannabinoid system was discovered at the beginning of the 1990s when researchers were trying to understand how tetrahydrocannabinol (THC), the psychoactive compounds in cannabis, affects the body. They found two main classes of receptors: CB1 cannabinoid receptors primarily in the brain and central nervous system and the CB2 receptors located mostly in the immune system, but also peripheral nerve terminals.
Binding with these cannabinoid receptors are fatty ligands called endocannabinoids; the most studied being anandamide and 2-AG, but may also include the related endogenous compounds arachidonic acid (AA), N-palmitoylethanolamine (PEA), and N-oleoylethanolamine (OEA)). Endocannabinoids are produced on demand when there is some imbalance in the body, after which they are broken down by special enzymes (FAAH and MAGL)
The ECS by its very nature is adaptive and dynamic, becoming altered in most pathological conditions, including pain. These changes can include alterations in cannabinoid receptor expression or their agonists, anandamide and 2-AG. However, this is thought to be protective in nature and is in effect our bodies trying to inhibit disease progression.
So far, most studies examining the role of the ECS in osteoarthritis have been carried out in animal models, usually rodents. While these give a strong indication of the relationship between the ECS and osteoarthritis, the results from the studies aren’t necessarily replicated in humans. In fact, one of the only human clinical trials targeting the endocannabinoid system for arthritis (blocking the enzyme responsible for breaking anandamide down in the body), failed to repeat the pain relieving results seen in animals.
That said, some useful clues to the role of the ECS in osteoarthritis have been highlighted through studies on mice and rats. Raised levels of anandamide, 2-AG and related compounds PEA and OEA were found in the spinal cord of rats induced OA knee pain. Another study found decreased CB1 and CB2 expression in the lumbar cord of mice induced with OA, which may be in response to increased ECS tone.
But how about in humans? While it’s a lot easier to measure endocannabinoid tone in rodents, one study did find OA patients had upregulated CB1 and CB2 expression as well as elevated 2-AG levels, suggesting a connection between the ECS, OA, and the higher rates of depression encountered by patients.
Could it be then that endocannabinoid dysregulation will become the osteoarthritis biomarker of the future, alerting doctors to the disease before too much joint damage has occurred?
What is certainly an area of exciting research is the development of drugs targeting the ECS as a way to reduce OA pain.
The role of the CB2 receptor, which when activated is known to have an anti-inflammatory effect, shows particular promise with scientists suggesting it may play a crucial role in modulating osteoarthritis. In one study, an increase in CB2 expression brought about a reduction in joint pain, while stimulating CB2 receptors in osteoarthritic rats reduced pain-associated behaviour. In fact, when scientists bred mice without any CB2 receptors at all, their OA was more severe than the control group.
Activating CB1 receptors also appears to suppress OA nociceptive pain, something scientists discovered using a synthetic CB1 agonist in a rodent model of osteoarthritis.
Cannabis & Osteoarthritis
With the ECS now an accepted therapeutic target for osteoarthritis drugs, this gives further foundation for the use of compounds within the cannabis plant to manage OA symptoms.
The cannabis plant contains more than 144 compounds called cannabinoids, with tetrahydrocannabinol (THC) perhaps the most widely studied. THC is a partial agonist for both CB1 and CB2 receptors, which could explain why patients find cannabis helps with their pain symptoms. Interestingly, one neuroimaging study in human subjects found THC reduced the unpleasantness of pain rather than changing pain sensations themselves.
THC is not always easily tolerated due its psychoactive effect, that’s why in some studies on humans for pain, it has been combined with the non-intoxicating cannabinoid, Cannabidiol (CBD).
As well as counteracting the “high” caused by THC, CBD is both analgesic and anti-inflammatory in its own right, through non-ECS mechanisms. However, CBD is thought to indirectly affect endocannabinoid tone by inhibiting the enzyme FAAH, responsible for breaking anandamide down in the body, which may bring about a further anti-inflammatory effect.
Indeed, one preclinical trial on rats found that CBD’s anti-inflammatory effect prevented pain and nerve damage associated with OA.
So far, cannabinoids have shown most efficacy in targeting neuropathic pain in humans, although anecdotal evidence from around the world suggests the cannabis plant is effective for chronic pain in general.
When it comes to osteoarthritis, clinical research has been limited, although right now two clinical trials using cannabinoids for OA are taking place.
The first, a randomised, double placebo trial, is studying the use of vaporized cannabinoids for arthritis of the knee joint. Different ratios of THC and CBD are being tested on 40 subjects for safety, efficacy and tolerability of the different cannabinoid combinations.
A second study, also random and placebo controlled, will study CBD as a treatment in osteoarthritis of the hand in 180 subjects.
Thankfully, more clinical research into cannabinoids for osteoarthritis is likely to take place worldwide as restrictions on researching compounds in cannabis become lifted.
While arthritis comes in different forms, over 100 in fact – osteoarthritis (OA) is the most common, affecting as estimated 350 million people around the world. All types of arthritis cause pain and inflammation in the joints, but they have different causes and affect people in different ways. Inevitably, as we age, our joints undergo a degnerative process which may lead to osteoarthritic change.
Osteoarthritis is when your joints are damaged by simple wear and tear of life. The joints that are worst affected are generally the ones that have been used the most during your life, usually weight-bearing joints though it can occur in any joint throughout the body.
Osteoarthritis is most common in your knees, hips, spine, and hands, but it can affect any joint in the body. Osteoarthritis of the knee is the most common, affecting 50% of adults at some point in their lives, followed by OA in the hips, affecting one in four people by the age of 85, while one out of every 12 people aged over 60 develops hand osteoarthritis.
The main symptoms of osteoarthritis are painful, stiff joints that hurt when you move them. You might find that your joints hurt when you press them gently, and see swelling around the joint.
Many people with osteoarthritis can’t move their joints through a full range of movement. You might feel the ends of bones grating against each other, especially in your knee, and hear popping or cracking when the joint moves. Some people also feel bone spurs, which are hard lumps of bone that form around the affected joint.
When to see a doctor
If you have joint pain and stiffness that doesn’t go away for several weeks, you should see your doctor. There are ways that they can ease the pain and discomfort and help keep you mobile and independent.
To diagnose osteoarthritis, your doctor will ask questions about your symptoms and your medical history. They will do a thorough physical examination, including checking each one of your joints for stiffness, pain, swelling, and range of motion/flexibility.
They’ll usually also do some or all of these tests:
- MRIs (magnetic resonance imaging) produces a detailed image of your bones and soft tissues, revealing areas of early damage from osteoarthritis.
- X-rays show bone deformity and may show cartilage loss, by demonstrating narrower space between the bones in your joints.
- Joint fluid analysis involves numbing the affected joint, then using a needle to draw out some fluid from the joint space. The doctor will examine the fluid for crystals or joint deterioration, and test it for signs of inflammation, to help rule out other medical conditions like gout or infection.
- Blood tests don’t reveal osteoarthritis, but they do help to rule out other conditions like rheumatoid arthritis and other conditions that impact the joints.
Joints are located in between bones, to allow us flexibility and the ability to move our fingers, limbs and spine. These joints are cushioned by a layer of cartilage around the end of each bone, to make it glide smoothly past all the other parts of your joints. Over time, this cartilage gets worn away and/or breaks down. The ends of the bones start to rub against each other, causing swelling, pain, and problems moving your joint.
Bits of bone or cartilage can break off and float around the joint. The inflammation that results from the rubbing bones produces proteins, called cytokines, and enzymes that damage the cartilage even more until bone rubs directly against bone.
When the bones rub together, it affects the bones, the connective tissues which hold the joint together and attach the muscles to the bones, and the lining that surrounds the whole joint.
There are some factors which make it more likely that you’ll develop osteoarthritis, or speed up the process. These include:
- Obesity- The more you weigh, the more pressure there is on your weight-bearing joints, especially your knees and hips. Fat tissue also produces proteins that cause inflammation in and around your joints, damaging the cartilage even more.
- Repetitive strain.- If you play a sport or do a job that repeatedly strains your joints, it’s going to speed up the damage to the cartilage in that joint.
- Heredity- If you have a family history of osteoarthritis, it’s slightly more likely that you’ll develop it too.
- Age- The older you are, the more likely you are to develop osteoarthritis.
- Gender- Women are more likely to get osteoarthritis than men, although scientists are not sure why.
- Metabolic diseases- Diabetes, hemochromatosis (a condition that occurs when your body produces too much iron), and some other metabolic disorders, can increase the likelihood of osteoarthritis.
- Joint injuries- Even if you were injured many years ago, and the injury completely healed, you’re still more likely to get osteoarthritis in that joint.
- Bone deformities- If you’re born with malformed joints or poor cartilage, you’re more likely to develop osteoarthritis.
- Immobility– Prolonged periods of inactivity can lead to progression of arthritis and joint and bone degeneration.
Osteoarthritis is a chronic and often progressive condition, which means that it can’t be cured. However, there are ways that you can ease the symptoms of osteoarthritis. Many people ignore their osteoarthritis or don’t go to seek treatment, because they don’t think that there’s anything they can do to make it better. Actually, it’s important to do as much as possible to reduce your symptoms of osteoarthritis in order to stay mobile.
If left untreated, the pain and discomfort of osteoarthritis can lead to loneliness due to avoiding social situations, having to stop working earlier than planned, and a sedentary lifestyle that leads to other health issues, like heart disease or diabetes.
Physical therapy and exercise
Although joint pain can make you want to stay as still as possible, it’s important to keep moving. Low-impact exercise, combined with physical therapy, helps strengthen the muscles that support your joints and relieve pressure on the joint itself. Gentle stretching and exercises to improve your range of motion help to ease stiff joints and keep them as supple as possible. Tai chi and yoga are particularly recommended for osteoarthritis.
Occupational therapists help you to find assistive devices that make it easier for you to do everyday tasks that might cause pain and discomfort. They also suggest mobility aids and adjustments to help you remain independent for longer.
If you’re overweight, losing weight can help to reduce the amount of pressure on your joints and decrease your pain and discomfort.
NSAIDs like aspirin, Advil (ibuprofen) and Aleve (naproxen) are anti-inflammatories that help reduce inflammation and relieve the pain of osteoarthritis. You can take them as pills, or apply them directly to the painful joint in the form of a gel.
Analgesics are any type of painkiller that helps you to manage the pain of osteoarthritis so that it doesn’t prevent you from living your regular daily life.
If oral medications don’t work, you might be prescribed a corticosteroid or hyaluronic acid injections. Corticosteroids are powerful anti-inflammatories that suppress the immune system, therefore reducing swelling and can provide significant pain relief. However, they also lead to other adverse effects such as bone loss, elevated sugar and a host of other problems, so you’ll only get them three or four times a year, maximum. Hyaluronic acid is a fluid that occurs naturally in your joints to lubricate them, but it seems to be lacking in people with osteoarthritis.
When osteoarthritis progresses to more advanced stages, often surgery can provide benefit and improve quality of life.
If your joints are severely damaged, joint replacement surgery can be a viable option. It replaces your damaged joint with a new one made of plastics and metal, which slides more smoothly against the rest of the joint. Surgery also carries its own risks and complications, and is almost never the only solution. Replacement joints can come loose, or wear out themselves.
Natural and alternative therapies
There are a number of alternative, natural, and herbal therapies that can relieve the pain of osteoarthritis. Some of them include:
- Heat and cold. Heat helps the muscles relax and ease stiffness. Cold relieves pain and aches in the muscles after exercise.
- Acupuncture and massage help reduce pain and stiffness in your joints.
- Relaxation techniques and meditation can help improve your state of mind, which makes it easier to bear osteoarthritis pain.
- Capsaicin is a chili pepper extract that’s applied directly to the painful joint to reduce inflammation and pain, but some people find that it causes too much skin irritation.