Do Joint Supplements Actually Work? New Research Review Examines Supplements for Canine Osteoarthritis
If you've practiced veterinary medicine for more than a minute, you've fielded the question: "Should I give my dog glucosamine?" As osteoarthritis remains one of the most common conditions we manage in canine patients, the promise of disease-modifying osteoarthritic drugs (DMOADs) that could actually alter disease progression—not just mask symptoms—is incredibly appealing. But do these supplements live up to their marketing claims?
A new review published in the Journal of Veterinary Medical Science tackles this question head-on, examining the clinical efficacy and safety of DMOADs with particular focus on glucosamine (GlcN) and pentosan polysulfate (PPS). Lead author Eugene C. Bwalya and colleagues evaluated these treatments against the rigorous outcome measures prescribed by the European Medicines Agency (EMA), and their findings are worth discussing with your clients—and perhaps reconsidering in your own treatment protocols.
The DMOAD Promise: Beyond Symptom Management
Let's start with why this matters. We all know that NSAIDs remain the frontline therapy for canine OA, and for good reason—they work. But here's the catch: NSAIDs control pain and inflammation without addressing the underlying pathophysiological destruction happening in the joint. They're essential for quality of life, but they're not changing the disease trajectory.
DMOADs represent a different approach entirely. These agents theoretically target the pathophysiologic processes of OA with the goal of preventing, slowing, or even reversing the morphologic changes associated with the disease. If they work as advertised, DMOADs could fundamentally change how we manage OA—shifting from symptom control to actual disease modification.
That's a big "if."
What the Research Actually Shows
Bwalya and colleagues conducted a systematic review of clinical studies examining GlcN and PPS, looking specifically at whether these widely-used supplements demonstrate meaningful clinical efficacy when evaluated by EMA standards. These standards exist for a reason—they help separate genuine therapeutic effects from placebo responses, subjective bias, and the natural variability we see in OA progression.
The review is particularly timely given how common these recommendations have become in veterinary practice. Glucosamine, often combined with chondroitin sulfate, is probably the most frequently recommended supplement for canine OA. PPS, administered by subcutaneous or intramuscular injection, has gained popularity as a more aggressive DMOAD option. But popularity doesn't equal efficacy.
Glucosamine: The Supplement Everyone Recommends
The evidence for glucosamine is... complicated. While numerous in vitro and experimental studies have suggested potential benefits, translating those laboratory findings into consistent clinical outcomes has proven challenging. Some studies show modest improvements in mobility and pain scores; others show no significant difference from placebo.
Part of the challenge is bioavailability. Oral glucosamine faces significant obstacles in reaching joint tissues in therapeutically relevant concentrations. Even when it does reach the joint, questions remain about whether it can meaningfully impact the complex cascade of inflammatory mediators and matrix-degrading enzymes driving OA progression.
The review highlights a critical issue many of us overlook: effect size. Even when studies show statistically significant improvements with glucosamine supplementation, the clinical significance of those improvements is often questionable. A statistically significant reduction in lameness scores sounds impressive until you realize the actual difference may not be perceptible to owners or meaningful for the patient's quality of life.
Pentosan Polysulfate: The Injectable Alternative
PPS has been marketed as a more potent DMOAD option, with proposed mechanisms including stimulation of hyaluronic acid synthesis, inhibition of degradative enzymes, and anti-inflammatory effects. The injection route theoretically bypasses bioavailability concerns that plague oral supplements.
But again, the clinical evidence is mixed. While some studies report improvements in mobility and pain scores, others fail to demonstrate clear advantages over placebo or standard NSAID therapy. The review emphasizes that many PPS studies have methodological limitations—small sample sizes, lack of appropriate controls, or subjective outcome measures—that make definitive conclusions difficult.
The Safety Question
One area where both GlcN and PPS generally perform well is safety. Compared to long-term NSAID use, both supplements have favorable adverse effect profiles. Glucosamine occasionally causes mild gastrointestinal upset, but serious adverse reactions are rare. PPS has been associated with bleeding tendencies in some cases (due to its heparin-like structure), but these effects are typically manageable.
This favorable safety profile is part of their appeal, particularly for older patients with comorbidities or those requiring long-term management. Even if efficacy is modest, low risk of harm makes them reasonable adjunctive options—as long as we're honest with clients about what we do and don't know.
What This Means for Your Practice
So where does this leave us? The review doesn't deliver the clear "yes" or "no" answer we might want, and that's probably the most honest conclusion available given current evidence.
Here's what we can reasonably tell clients:
DMOADs are not miracle cures. Despite marketing claims, current evidence doesn't support the idea that glucosamine or PPS fundamentally alter OA progression in most dogs. They're not going to regenerate cartilage or reverse joint damage.
Some patients may experience modest benefits. Individual responses vary, and some dogs do seem to show improvements in mobility and comfort when supplemented with GlcN or treated with PPS. Whether this represents genuine pharmacological effects, placebo-by-proxy (owners perceiving improvement), or natural disease fluctuation remains unclear.
Safety profiles are generally favorable. For clients looking for "something else" beyond NSAIDs, these options carry relatively low risk. That makes them reasonable to try, especially as adjunctive therapy.
NSAIDs remain the evidence-based standard. Until stronger evidence emerges for DMOADs, NSAIDs should remain our primary pharmacological intervention for managing OA pain and inflammation.
Multimodal management is key. Rather than relying on any single intervention, the best outcomes come from combining pharmacological management (primarily NSAIDs) with weight management, controlled exercise, physical rehabilitation, and environmental modifications.
The Bigger Picture
This review serves as a valuable reminder to approach supplement recommendations with the same evidence-based scrutiny we apply to pharmaceutical interventions. The fact that something is "natural" or has a favorable safety profile doesn't exempt it from requiring solid efficacy data.
It's also worth acknowledging the challenge of conducting high-quality clinical research on chronic conditions like OA. Placebo responses are significant, disease progression is variable, and measuring meaningful clinical outcomes is complex. The review appropriately applies EMA standards precisely because these rigorous criteria help us distinguish genuine therapeutic effects from confounding variables.
Moving Forward
For veterinarians already recommending glucosamine or PPS, this review doesn't necessarily mean you need to stop. But it does suggest we should be more measured in our claims and clearer with clients about evidence limitations.
Consider framing these recommendations as: "Some dogs seem to benefit from these supplements, though the scientific evidence is mixed. They're generally safe, so they're worth trying as part of a comprehensive management plan. Let's reassess in 6-8 weeks to see if your dog shows meaningful improvement."
That's honest, evidence-based, and appropriately cautious—which is exactly the standard we should apply to all our therapeutic recommendations.
The Bottom Line
DMOADs represent an appealing concept: medications that don't just mask OA symptoms but actually modify disease progression. Unfortunately, current evidence for glucosamine and pentosan polysulfate doesn't strongly support that promise. While generally safe and possibly providing modest benefits in some patients, these agents haven't demonstrated the disease-modifying effects that would justify their widespread use as primary OA therapies.
Until better evidence emerges, our OA management approach should remain grounded in proven interventions: NSAIDs for pain control, weight management, appropriate exercise, and physical rehabilitation. DMOADs can play a supporting role, but they shouldn't be oversold to clients desperate for solutions to their dogs' chronic joint disease.
Full Text Link: A review of the clinical efficacy and adverse effects of disease modifying osteoarthritic drugs (DMOADs) in dogs with special focus on glucosamine and pentosan polysulfate; do they work? - Journal of Veterinary Medical Science, published online October 31, 2025.
