Volume II: Pain, Joint Inflammation and Equine Comfort

Volume II: Pain, Joint Inflammation and Equine Comfort

Volume II: Pain, Joint Inflammation and Equine Comfort

Purpose of this volume

This section examines whether cannabinoids have been officially studied for pain, arthritis, inflammation or physical comfort in horses.

The equine evidence is still small, but researchers have now studied:

  • Horses with naturally occurring osteoarthritis

  • Cannabinoid receptors in equine joints

  • Experimental pain sensitivity in healthy horses

  • Whether oral CBD reaches equine joint fluid

  • Cannabinoids as part of palliative care in a severely injured horse

The available research does not yet establish topical THC as a proven treatment for equine arthritis.

Study 1: CBD and Mild Osteoarthritis in Horses

Improved Quality of Life and Pain Relief in Mature Horses With Osteoarthritis Following Oral Cannabidiol Administration

Published: 2024
PubMed:
https://pubmed.ncbi.nlm.nih.gov/38379920/

Type of study

Randomized controlled equine clinical study.

Horses studied

Twenty mature horses with mild joint osteoarthritis.

What researchers tested

The horses were assigned to two groups:

  • A control group

  • A CBD group

Both groups received phenylbutazone for five days. The CBD group also received oral CBD in hemp oil once daily for 14 days.

Researchers evaluated clinical signs associated with osteoarthritis, including pain, lameness and quality of life.

What researchers reported

The horses receiving CBD alongside the conventional treatment showed improvements in measures of pain and quality of life compared with the control group.

This is important because the study involved living horses with naturally occurring joint disease rather than isolated cells or healthy horses alone.

What this study supports

This study provides preliminary clinical evidence that orally administered CBD might have value as an additional therapy for some horses with mild osteoarthritis.

Important limitations

  • Only 20 horses participated.

  • The horses had mild osteoarthritis.

  • The CBD group also received phenylbutazone.

  • CBD was administered orally, not topically.

  • The study did not test THC.

  • The CBD dose and formulation cannot automatically be applied to other products.

Responsible conclusion

A small equine clinical study reported improved comfort and quality-of-life measures when oral CBD was added to conventional treatment for mild osteoarthritis.

It would be inaccurate to say:

CBD or THC has been proven to cure equine arthritis.

Study 2: Cannabinoid Receptors in Inflamed Equine Joints

Cannabinoid Receptors Are Expressed in Equine Synovium and Upregulated With Synovitis

Published: 2023
Journal: Equine Veterinary Journal
PubMed:
https://pubmed.ncbi.nlm.nih.gov/35836386/

Type of study

Laboratory study of equine joint tissue.

What researchers examined

Researchers investigated the synovium, which is the tissue lining the inside of a joint.

They compared cannabinoid-receptor expression in normal and inflamed equine synovial tissue.

What researchers found

CB1 and CB2 cannabinoid receptors were identified in equine synovial tissue. Their expression changed or increased in association with synovitis, which is inflammation of the joint lining.

The researchers described these receptors as possible future therapeutic targets for equine joint inflammation and pain.

Why this matters

Osteoarthritis commonly involves:

  • Synovial inflammation

  • Joint pain

  • Reduced mobility

  • Progressive cartilage damage

The presence of cannabinoid receptors in this tissue means that the equine endocannabinoid system may participate in how a joint responds to inflammation.

What this study does not prove

The researchers did not treat arthritic horses with cannabis.

The study does not show:

  • That THC reduces equine joint pain

  • That CBD reverses arthritis

  • That a topical balm reaches the synovium

  • What dose or formulation would be effective

  • Whether long-term treatment would be safe

Responsible conclusion

Equine joint tissue contains cannabinoid receptors, and receptor activity appears to be associated with synovial inflammation. This gives researchers a biological reason to investigate cannabinoid-based joint therapies.

Study 3: CBD and Experimental Pain Sensitivity

Oral Cannabidiol Increases Thermal Threshold in Horses Without Physiologic Adverse Effects

Published: 2025
Journal: American Journal of Veterinary Research
PubMed:
https://pubmed.ncbi.nlm.nih.gov/40854532/

Type of study

Controlled experimental study in horses.

What researchers measured

Researchers used a thermal-threshold test.

A thermal-threshold test measures how much controlled heat stimulation is tolerated before the horse responds. It is one way researchers study pain sensitivity without causing an injury or creating arthritis.

The horses received oral CBD, and researchers monitored:

  • Thermal-pain threshold

  • Heart rate

  • Respiratory rate

  • Temperature

  • Sedation or behavioral changes

  • Other physiological effects

What researchers found

Oral CBD increased the horses’ thermal threshold. In simple terms, the horses responded at a higher level of thermal stimulation after receiving CBD.

No important physiological adverse effects were identified at the dose studied, and the treatment was described as well tolerated.

Why this matters

This is direct equine evidence that CBD may influence the way horses process or respond to a painful stimulus.

It moves the research beyond simply showing that cannabinoid receptors exist.

Important limitations

  • The horses were not necessarily suffering from chronic arthritis.

  • A controlled heat test is not the same as naturally occurring joint pain.

  • The study evaluated oral CBD, not topical CBD or THC.

  • An increased thermal threshold does not automatically mean improved mobility or quality of life.

  • Results apply only to the dose and formulation studied.

Responsible conclusion

Oral CBD altered thermal-pain sensitivity in horses under controlled research conditions and was well tolerated at the studied dose.

Study 4: Can Oral CBD Reach an Equine Joint?

Plasma Pharmacokinetics, Short-Term Safety and Synovial Fluid Levels Following Oral CBD Administration

Published: 2022
PubMed:
https://pubmed.ncbi.nlm.nih.gov/35307550/

Type of study

Prospective, randomized and controlled equine study.

What researchers tested

Horses received single and repeated oral doses of CBD.

Researchers measured:

  • CBD concentrations in blood plasma

  • CBD and metabolite concentrations over time

  • Short-term safety measurements

  • CBD concentrations in synovial fluid

Synovial fluid is the lubricating fluid inside movable joints.

What researchers found

CBD or its related compounds could be measured following oral administration, including in samples associated with the joint environment.

The study provided information about dosing, absorption and short-term tolerability.

Why this matters

For an orally administered compound to affect a joint directly, it generally needs to be absorbed and distributed to relevant tissues.

Finding CBD-related compounds in synovial fluid supports the possibility that oral CBD can reach the equine joint environment.

What this study does not prove

The study did not establish that CBD:

  • Reduced arthritis pain

  • Improved lameness

  • Repaired cartilage

  • Reduced synovitis

  • Reached a clinically effective concentration

Detection is not the same as therapeutic effectiveness.

Responsible conclusion

Oral CBD can be absorbed by horses, and CBD-related compounds can reach the joint environment. Clinical trials are still needed to determine whether those concentrations improve pain or inflammation.

Study 5: THC and CBD in Equine Palliative Care

Oral and Topical Chronic Administration of THC-Rich and CBD-Rich Cannabis Oils in a Horse

Published: 2026
Type: Equine clinical case report
PubMed:
https://pubmed.ncbi.nlm.nih.gov/42311392/

Horse described

The report involved a senior rescued gelding with multiple severe problems, including:

  • A large chronic ulcerative lesion

  • Severe malnutrition

  • Non-weight-bearing lameness

  • Refractory pain

  • Suspensory-tendon rupture

  • Early osteomyelitis

  • Chronic joint disease

  • An equine sarcoid

What treatment was used

The palliative-care plan included both THC-rich and CBD-rich full-spectrum cannabis oils.

The oils were administered orally, while the formulation was also applied topically to the wound. Cannabinoids were used as part of a broader multimodal care program rather than as the horse’s only treatment.

What was reported

During the treatment period, the authors reported improvements in areas including:

  • Appetite

  • Body condition

  • Pain

  • Mobility

Treatment continued for approximately 10 months. The authors concluded that controlled research is still needed to establish appropriate doses and uses.

Why this study matters

This appears to be one of the most directly relevant published equine reports involving:

  • THC

  • CBD

  • Topical administration

  • Chronic pain

  • Mobility

  • Long-term palliative care

Why it must be interpreted carefully

This was a single case report, not a randomized clinical trial.

The horse also received other treatments. Therefore, the report cannot determine:

  • Which treatment caused the improvement

  • Whether THC was necessary

  • Whether topical treatment contributed independently

  • Whether the same approach would be safe for another horse

  • Whether it would treat ordinary equine arthritis

  • What effects would occur in a healthy or competition horse

A case report provides a documented clinical observation. It does not prove cause and effect.

Responsible conclusion

A 2026 case report documented long-term oral and topical THC-rich and CBD-rich cannabis use as part of multimodal palliative care for one severely compromised horse. Reported improvements justify further study, but the case does not establish safety or effectiveness for the wider equine population.

Study 6: The Endocannabinoid System as a Pain and Inflammation Target

Equine Endocannabinoid-System Research and Potential Pharmacological Targets

Published: 2025
PubMed:
https://pubmed.ncbi.nlm.nih.gov/41394912/

Type of research

Equine-focused scientific research examining the endocannabinoid system as a possible therapeutic target.

Scientific basis

The endocannabinoid system participates in biological processes connected to:

  • Pain signaling

  • Inflammatory responses

  • Immune activity

  • Cell proliferation

  • Tissue regulation

Researchers are studying whether changing this system could eventually help manage equine inflammatory or painful conditions.

Why this matters

Cannabinoid research is not based only on the cannabis plant.

Researchers may investigate:

  • Naturally produced equine endocannabinoids

  • CB1 receptors

  • CB2 receptors

  • Cannabinoid-related receptors

  • Enzymes that create or break down endocannabinoids

  • Drugs that affect these pathways without using THC

Important distinction

Identifying a biological target does not mean researchers already have an approved or proven treatment.

What Volume II Shows Overall

What has been demonstrated in horses

Research has shown that:

  • Equine joint tissue contains cannabinoid receptors.

  • Cannabinoid-receptor expression is associated with joint inflammation.

  • Oral CBD can be absorbed and distributed within the horse.

  • CBD-related compounds can reach the equine joint environment.

  • Oral CBD can influence thermal-pain sensitivity under controlled conditions.

  • A small clinical study reported improved comfort in horses with mild osteoarthritis receiving CBD alongside conventional treatment.

  • One case report described oral and topical THC-rich and CBD-rich cannabis use in equine palliative care.

What has not been established

Current equine research has not yet proven that:

  • Topical THC reliably relieves equine arthritis.

  • A cannabis balm penetrates deeply enough to treat an equine joint.

  • THC is safe for routine topical use in horses.

  • CBD or THC can repair cartilage or reverse arthritis.

  • Findings from one product apply to all cannabis products.

  • Cannabinoids should replace established veterinary pain treatment.

  • There is a standardized therapeutic dose for equine pain.

  • Long-term cannabinoid use is safe for all horses.

Best Evidence-Based Summary

Early equine research suggests that the endocannabinoid system participates in joint inflammation and pain processing. Oral CBD has affected pain sensitivity in controlled testing, reached the joint environment and shown preliminary benefits in a small osteoarthritis study. A recent case report has also documented THC-rich and CBD-rich cannabis use in equine palliative care. However, controlled studies of topical THC for equine arthritis remain lacking.

Educational Statement for Everwild Ranch

Horses possess cannabinoid receptors in tissues involved in joint inflammation and pain signaling. Equine studies have begun examining CBD absorption, joint-fluid exposure, osteoarthritis symptoms and pain sensitivity. The early findings support continued research, but topical THC has not yet been proven as a standardized treatment for equine arthritis.

Research Status

Strongest equine evidence

  • Cannabinoid receptors exist in equine joint tissue.

  • Oral CBD is absorbed by horses.

  • Oral CBD can affect experimentally measured pain sensitivity.

Preliminary equine evidence

  • Oral CBD may support comfort in some horses with mild osteoarthritis.

  • Cannabinoid therapy may have a future role in equine palliative care.

Major research gap

  • Controlled trials evaluating topical THC or CBD for naturally occurring equine joint pain and arthritis.