Cannabis affects the endocannabinoid system, which is a system in the body that regulates various functions including pain. Modulating the endocannabinoid system could potentially help to alleviate knee pain through stimulating cannabinoid receptors that regulate pain signaling.
Dozens of studies have shown that cannabis helps with pain. To date, there are no human studies published specifically looking at cannabis and knee pain. Since we do have studies showing cannabis helps with joint pain in conditions such as osteoarthritis that cause knee pain, it’s reasonable to assume that cannabis may also help with this specific pain. However, exactly how effective cannabis is for knee pain is a question that can only be answered after specific studies are done.
Furthermore, multiple strains of cannabis have been identified that have different chemical profiles. Nevertheless, research is lacking regarding which strains would be most efficacious for specific conditions.
How cannabis works on knee pain
The endocannabinoid system (ECS) exists in all vertebrates and helps regulate crucial functions such as sleep, pain, and appetite. The human body produces its own cannabinoids, which modulate and activate its various functions, but as its name suggests, the endocannabinoid system can also be modulated and activated by cannabinoids found in the cannabis plant. Because the entire system was only discovered in the past 30 years, scientists still have much to learn about the myriad ways cannabis affects the human body.
A large body of evidence has confirmed that the endocannabinoid system is involved in pain regulation. More specifically, CB1 and CB2 receptors are the two receptors in the endocannabinoid system that regulate pain.
CB1 receptors are densely cumulated in frontal-limbic brain regions which regulate emotional manifestations of pain. CB2 receptors are abundant in immune cells and represent a target for affecting inflammatory processes.
Originally CB2 receptors were thought to exclusively be found on immune cells, but more recent research has shown CB2 receptors are expressed on neural cells involving pain perception.
There is evidence that the synovium, soft tissue membrane that lines spacing of diarthrodial joints, tendon sheaths, and bursae, plays a considerable role in the cause of knee pain caused by osteoarthritis. CB1 and CB2 receptors are expressed in the synovium of osteoarthritis and rheumatoid arthritis patients. According to researchers, the presence of cannabinoid receptors in this membrane may indicate the endocannabinoid receptor system is an important therapeutic target for treating the pain associated with these conditions.
Research has also looked at how targeting the endocannabinoid system could alleviate inflammatory flares and pain in mouse knee joints. In one study, researchers induced acute joint inflammation and pain in mouse knee joints. After examining the knee joints for the presence or absence of CB1 and CB2 antagonists, they found that the endocannabinoid system can be harnessed to decrease knee pain.
The endocannabinoid system and knee pain seem to naturally be associated with one another. Altering the endocannabinoid system may, therefore, help with knee pain.
Research on knee pain and cannabis
Studies have made it clear that cannabis helps with chronic pain. Many of the studies looking at cannabis and chronic pain have examined conditions that affect joints such as osteoarthritis.
The following studies give an overview of cannabis’s effects on chronic pain and joint-specific pain.
- One review of 28 studies on cannabis and chronic pain led researchers to conclude that “there was moderate-quality evidence to support the use of cannabinoids for the treatment of chronic pain.”
- In a 2016 review, researchers set out to answer the question, “Is cannabis an effective treatment for joint pain?” They concluded that based on the anecdotal evidence and preclinical and human data available, cannabis should be “taken seriously” as a potential treatment for joint pain.
The association between cannabis use and reductions in chronic pain (in general and in conditions affecting joints) is positive. What we still require are clinical trials examining the effects of cannabis on people with knee pain.
There is currently an undergoing randomized, double placebo trial investigating the use of vaporized cannabinoids for arthritis of the knee joint. Different ratios of THC and CBD are being administered on 40 subjects to test the safety, efficacy, and tolerability of various cannabinoid combinations. The trial was estimated to be completed in mid-2019 but still appears to be in progress.
CBD and knee pain
Both animal and human studies appear to show positive effects for CBD as a pain-reliever in conditions affecting the joints such as osteoarthritis and fibromyalgia.
- In a 2017 review, researchers examined how well CBD works for chronic pain. Researchers analyzed a pool of studies published between 1975 and 2018 which focused on cancer pain, neuropathic pain, and fibromyalgia. The researchers concluded that CBD helped to reduce pain and didn’t cause any adverse effects.
- In a 2016 study, researchers showed that in an animal model, topical CBD was able to decrease pain and inflammation caused by arthritis.
- In a 2017 study, researchers examined the effects of CBD on pain in rats with osteoarthritis. The results showed that CBD helped to decrease joint pain in a dose-dependent manner and prophylactic CBD administration was found to help reduce future developments of nerve damage and pain in arthritic joints.
- One randomized controlled trial is currently underway that will be investigating the effects of CBD as a treatment in osteoarthritis in 180 subjects. The trial is estimated to be completed in late 2020.
CBD is useful for pain relief, but whether CBD is effective for knee pain is yet to be determined. Human trials are needed to test whether CBD administered to people with knee pain helps reduce pain more than placebo.
Potential side effects of cannabis use
Cannabis is a safe medication to use for joint pain, and although it has potential side effects, it is a much safer option than opioids. Short term side effects of cannabis may include euphoria, perceptual changes, increased appetite, and changes to energy levels.
Long-term side effects are unlikely for infrequent users of small amounts of cannabis. Chronic use of cannabis — especially when started as an adolescent — can cause cognitive impairment later in life and increase the chances of addiction, which occurs in approximately one in ten people who use cannabis.
CBD has few side effects, but in some people, it may cause stomach discomfort and fatigue. CBD also has the potential to have negative interactions with certain blood thinners.
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