The newest knee injections fall into two categories: recently approved treatments you can get now and experimental therapies working through clinical trials. Among currently available options, some of the most notable recent additions include an autologous protein solution called nSTRIDE APS, an extended-release steroid formulation, and a coral-derived cartilage repair implant. On the experimental side, gene therapy injections and exosome-based treatments are in early clinical trials.
nSTRIDE Autologous Protein Solution
One of the newer injection-based treatments for knee osteoarthritis is nSTRIDE APS, which works by concentrating your own blood proteins into a single shot delivered directly into the joint. A small blood sample is drawn and processed in a bedside device that isolates anti-inflammatory proteins, particularly a natural substance your body produces to block inflammation signals. The concentrated solution is then injected back into your knee.
What makes nSTRIDE stand out is its durability. In a head-to-head trial comparing it to a standard hyaluronic acid injection (Synvisc-One), both groups saw roughly 40% pain reduction at 12 months. But at the four-year mark, the gap widened significantly: 80.6% of nSTRIDE patients were still experiencing meaningful pain relief from their original injection, compared to 62.7% in the hyaluronic acid group. Nearly 12% of nSTRIDE patients qualified as high responders, meaning they achieved 90% or greater pain improvement without needing regular pain medication. Only 3.3% of hyaluronic acid patients hit that threshold.
Extended-Release Steroid Injection
Traditional steroid injections for knee pain tend to wear off within a few weeks. Zilretta changed that by embedding the steroid in tiny biodegradable microspheres that dissolve slowly inside the joint, releasing medication gradually over about 12 weeks. In real-world use, the average patient went roughly 16 to 17 weeks before needing a second injection, and 74% of patients returned for their second dose between weeks 16 and 24.
This is a meaningful upgrade over conventional cortisone shots for people who find relief fades too quickly. The slow-release design also keeps more of the steroid inside the joint rather than leaking into the bloodstream, which may reduce the blood sugar spikes and other systemic effects that make some patients wary of repeated cortisone injections.
CartiHeal Cartilage Repair Implant
For patients with actual cartilage damage rather than general osteoarthritis wear, the CartiHeal Agili-C implant represents a different approach entirely. This isn’t a traditional injection but a small implant made from aragonite, a form of calcium carbonate derived from coral skeletons. A surgeon places it into the damaged cartilage site during a minimally invasive procedure, and over time the body absorbs the implant while regenerating its own cartilage tissue in its place. UC Davis Health began performing the procedure in late 2023 following FDA approval, and it’s now available at select orthopedic centers.
Bone Marrow Concentrate vs. PRP
Platelet-rich plasma (PRP) has been a popular regenerative injection for years, but bone marrow aspirate concentrate (BMAC) is increasingly positioned as the more potent option for knee osteoarthritis specifically. BMAC is drawn from your hip bone, processed to concentrate stem cells and growth factors, then injected into the knee. Lab comparisons show BMAC contains significantly higher levels of a key anti-inflammatory protein (the same one nSTRIDE concentrates) compared to PRP. It also contains stem cells that PRP simply doesn’t have.
In one clinical study, ten patients treated with a combination of BMAC and PRP for full-thickness cartilage lesions in the knee showed improvement in both pain and function scores at one and two years after treatment. The evidence suggests BMAC may be better suited for osteoarthritis because of its stronger anti-inflammatory profile, while PRP’s higher concentration of growth factors that promote blood vessel formation makes it potentially more useful for tendon and muscle injuries where healing and blood supply are the priority.
Neither PRP nor BMAC is covered by most insurance plans. Out-of-pocket costs typically range from $500 to $2,000 per PRP injection and $3,000 to $8,000 for BMAC, depending on the provider and region.
Gene Therapy Injections in Clinical Trials
The most futuristic option currently being tested is FX201, a gene therapy injection in Phase 1 clinical trials. Instead of delivering a drug that wears off, FX201 uses a modified virus to deliver a gene directly into the cells lining your knee joint. Those cells then produce their own anti-inflammatory protein on an ongoing basis, essentially turning your joint into its own treatment factory. The gene is designed with an inflammation-sensitive switch, meaning it ramps up production when inflammation is active and dials back when it’s not. This is still early-stage research, so it’s not available outside of trials.
Exosome therapy is another experimental approach. Exosomes are tiny communication packets released by stem cells that appear to stimulate cartilage repair without requiring the stem cells themselves. PRP-derived exosomes have shown even stronger cartilage-protective effects than PRP alone in lab studies. The main bottleneck is that current technology for extracting and purifying exosomes reliably enough for clinical use hasn’t caught up to the science.
What to Expect After a Knee Injection
Recovery from most knee injections is straightforward. The first 24 hours should involve relative rest to allow the injected material to absorb properly and to monitor for any reaction. For steroid and hyaluronic acid injections, you can begin light activity like stationary cycling or bodyweight exercises 24 to 48 hours afterward, then gradually increase intensity.
The most common side effect across all knee injections is temporary pain and swelling at the injection site. For hyaluronic acid injections specifically, adverse reaction rates run between 3.7% and 8.5%, though clinical trials show these rates are essentially the same as placebo injections, suggesting much of the discomfort comes from the needle itself rather than the substance. A small number of patients experience what’s called a severe acute localized reaction: significant swelling, redness, and restricted motion that typically starts 4 to 12 hours after the injection. This looks alarming but is far more common than actual infection and usually resolves on its own. Ice and over-the-counter pain relievers are generally enough to manage it.
If you have a known allergy to hyaluronic acid products or, in the case of bird-derived formulations, allergies to eggs or feathers, let your provider know before the procedure. Avoiding strenuous activity for 48 hours after any injection helps the treatment stay concentrated in the joint rather than getting flushed into the bloodstream through increased circulation.