For millions of people living with osteoarthritis, the daily reality is often defined by a persistent, grinding cycle of pain, joint stiffness, and a steadily declining ability to perform everyday activities. Common medical treatments, ranging from readily available over-the-counter pain medications to targeted steroid injections, may temporarily blunt the sharpest edges of these symptoms. However, medical science has long recognized a critical limitation in these conventional therapies: none of them possess the ability to halt or reverse the underlying structural joint damage that drives the disease forward.
A breakthrough study led by researchers at Yale University now suggests a radically different therapeutic paradigm. In findings recently published in the scientific journal Bioactive Materials, a team of scientists has demonstrated that the established medication lacosamide can serve a dual purpose in the fight against osteoarthritis. Not only does the drug successfully reduce joint pain, but it also actively reverses cartilage damage. Crucially, these regenerative and analgesic effects were shown to be exceptionally strong when the medication was delivered directly inside the joint using a specialized, temperature-sensitive hydrogel.
Why Osteoarthritis Damages Cartilage
Osteoarthritis is frequently described in colloquial terms as a simple condition caused by routine wear and tear, but that characterization overlooks the complex and destructive biology driving the disease from within.
Within a healthy human joint, specialized cells known as chondrocytes are tasked with maintaining the integrity of the cartilage. They achieve this by constantly balancing the creation of new extracellular matrix tissue with the controlled removal of older material. Osteoarthritis fundamentally disrupts this delicate biological equilibrium. As the disease takes hold, cartilage begins to break down at a pace far faster than the chondrocytes can manufacture replacements. Eventually, this protective cushioning wears away entirely, leaving bare bones to rub painfully against one another. As the condition advances into its later stages, many patients find themselves facing invasive joint reconstruction procedures, including total knee replacements.
"There is a major unmet need in osteoarthritis," explains the study’s principal investigator, Chuan-Ju Liu, PhD, who serves as the Charles W. Ohse Professor of Orthopaedics & Rehabilitation at Yale. "We need therapies that don’t just mask pain but actually change how the disease progresses."
At present, there is not a single medication approved by the U.S. Food and Drug Administration that can simultaneously stop osteoarthritis pain and prevent the structural breakdown of cartilage. The pioneering work directed by Liu suggests that medical science may soon be able to address both halves of this clinical problem using a single, unified therapeutic strategy.
By taking an existing medication and pairing it with an advanced biomaterial designed to keep the drug localized within the joint, the Yale researchers have outlined an approach that could potentially preserve vital joint tissue while delivering sustained, potent pain relief entirely without relying on addictive opioids.
A Protein Linked to Pain and Cartilage Loss
The core of the Yale research centers on Nav1.7, a specific protein that functions as a voltage-gated sodium channel. These channels act as microscopic gates embedded within cell membranes, playing a fundamental role in the generation and propagation of electrical signaling throughout the body.
For years, the scientific and medical communities believed that Nav1.7 operated primarily within specialized peripheral nerve cells dedicated to transmitting pain sensations to the brain. Because of this presumed role, the protein had long been a target for various pain management drugs. However, more recent investigative work conducted by Liu and his research team revealed a surprising and previously unrecognized twist: Nav1.7 is also highly active in chondrocytes, the very cells responsible for building and maintaining healthy cartilage.
In a healthy joint, Nav1.7 remains relatively quiet and subdued. In an osteoarthritic joint, however, its activity increases dramatically. The researchers discovered that this pathological surge in activity serves a double blow. Not only does it intensely amplify pain signaling pathways, but it also actively pushes chondrocytes toward breaking down the very cartilage they are supposed to preserve.
This dual involvement makes Nav1.7 an unusually promising therapeutic target, as it exerts direct influence over both the subjective sensation of pain and the objective, physical deterioration of joint tissue.
"When Nav1.7 becomes dysregulated, it contributes to both joint degeneration and pain," Liu notes. "Our findings suggest that Nav1.7 is a dual-acting target. By blocking this single protein, we can potentially quiet the pain nerves and tell the cartilage cells to not only stop breaking down but start repairing as well."
Epilepsy Drug Shows Potential for Cartilage Repair
Rather than spending years attempting to design and synthesize an entirely new chemical entity from scratch, Liu’s team decided to test existing medications that are already known to inhibit sodium channels. Among the candidates evaluated, lacosamide stood out by producing remarkably strong biological effects at considerably lower concentrations, while simultaneously offering a much more favorable safety profile than older drugs belonging to the same pharmacological class.
Lacosamide is already an established prescription medication widely used in the medical field to treat epilepsy. Yet, when the Yale researchers examined its effects on joint tissue, they discovered that its impact on cartilage depended heavily on precise dosing parameters.
In this context, a higher dose was not necessarily better. At an optimal low concentration, lacosamide encouraged chondrocytes to manufacture the specific proteins required to build new cartilage while actively suppressing the destructive biochemical processes that break tissue down. When the drug concentration strayed outside this narrow window—becoming either too high or too low—those protective and regenerative benefits quickly faded away.
"This tells us the system is finely tuned," Liu observes. "There is an optimal range where the drug helps restore balance without overcorrecting. What stood out was not just its effectiveness, but how little of a dose was needed."
Further biochemical investigation revealed that lacosamide also alters the fundamental ways in which cells communicate with one another within the joint environment. Specifically, the drug was found to stimulate the release of two highly beneficial signaling proteins: HSP70 and midkine.
HSP70 is a well-known molecular chaperone that helps cells cope with cellular stress and actively supports tissue repair mechanisms. Meanwhile, midkine plays an important role in regulating inflammation and shielding joint tissue from progressive degeneration. Together, the presence of these two proteins appears to foster a biochemical microenvironment that is vastly more favorable for maintaining and restoring healthy cartilage.
"These proteins create a supportive environment for cartilage maintenance," Liu explains. "They allow the effects of the drug to extend beyond individual cells and influence the entire tissue."
Smart Hydrogel Keeps the Drug Inside the Joint
While initial preclinical testing demonstrated that oral administration of lacosamide could be effective, taking the medication by mouth means the drug circulates systematically throughout the entire body. This widespread distribution inherently increases the potential for unwanted side effects in unrelated organ systems.
To circumvent this limitation, the researchers turned their attention to intra-articular injection, a medical technique that allows a medication to be placed directly inside the cavity of the affected joint, delivering the therapeutic agent precisely where it is needed most.
Even with direct injection, however, a significant physiological obstacle remained. "The knee joint, which is also the most common location for osteoarthritis, naturally acts like a leaky bucket," Liu points out. "The body’s natural drainage system can clear out liquids injected into the knee within hours."
To keep the medication anchored in place for an extended period, the research team engineered a specialized hydrogel formulated from Collagen II. This advanced biomaterial possesses unique thermo-responsive properties. It remains in a free-flowing liquid state while stored inside a cool syringe, but rapidly transitions into a firm, gel-like matrix once it reaches normal human body temperature.
Once injected into the joint space, the smart hydrogel functions as a localized storage depot for lacosamide. It holds the medication securely within the affected area while gradually releasing the active compound in a controlled, sustained manner over the course of several weeks.
"The hydrogel acts as a local reservoir," Liu says. "It holds the drug in place in the location it is needed most and releases it slowly over time. It transforms a daily pill into a long-lasting, local treatment that stays active for a month or longer."
In the team’s preclinical studies, a single administration of the lacosamide-infused hydrogel once every four weeks proved significantly more effective at preventing cartilage loss than administering an oral dose of the drug every single day.
Existing Drug Could Speed Clinical Testing
One of the most significant practical advantages of utilizing lacosamide is that the medication is already fully approved by regulatory agencies for human use. This established clinical history could potentially enable researchers to move toward formal human clinical trials involving osteoarthritis patients much more rapidly than would ever be possible with a novel, unproven chemical compound.
Furthermore, lacosamide has already undergone human safety evaluations in clinical settings for specific nerve-related pain conditions linked to Nav1.7 mutations. These past human trials provide the research team with a greater degree of confidence that the promising results observed in laboratory and preclinical studies could eventually translate into safe, meaningful pain relief for everyday patients.
This work also reflects a broader, highly innovative direction in modern translational medicine, which seeks to combine existing pharmacological agents with advanced biomaterials to maintain precise spatial and temporal control over how treatments are delivered within the body. If this targeted delivery method ultimately proves successful in human clinical trials, it could substantially reduce the frequency of medical interventions required by patients, minimize systemic side effects, and offer much longer-lasting structural protection against progressive joint damage.
"We are not just developing a treatment," Liu concludes. "We are developing a system that allows the medicine to work more effectively where it matters most. Our goal is to move beyond symptom control and towards true disease modification. This effort brings us closer to that reality."