A gel-like supplement to the natural lubricating fluid in an arthritic joint — most commonly used in the knee. It is a joint injection (viscosupplementation), not a biologic, and one of the knee-osteoarthritis injections insurers most often cover.
Hyaluronic acid — HA for short — is a naturally occurring substance in your joint's synovial fluid. It's what gives that fluid its slippery, shock-absorbing quality. In an arthritic joint, the natural HA becomes thinner and less effective, and the joint moves less smoothly. A hyaluronic acid injection supplements that fluid with a gel-like product designed to mimic the HA your body makes. You'll sometimes hear this called "viscosupplementation" or, more casually, "gel shots."
There are several HA products on the market. Some are given as a single injection (such as Synvisc-One or Monovisc); others are given as a series of three to five weekly injections (such as Hyalgan, Supartz, or Euflexxa). Both approaches have supporting evidence and similar overall outcomes — the choice often comes down to insurance coverage and patient preference.
The strongest evidence for HA is in knee osteoarthritis, particularly after NSAIDs, physical therapy, and activity modification have stopped giving enough relief but joint replacement isn't yet on the table. It's often a reasonable next step before — or alongside — orthobiologic options like PRP.
HA is generally not the right choice when joint replacement is clearly indicated (severe, end-stage arthritis with mechanical symptoms), when there is active infection in or near the joint, or in the rare patient with a known allergy to a product component (some products are derived from avian sources). If you have a history of significant gout or other crystal arthritis flares, we'll discuss timing carefully.
We confirm the target joint, review your medications, and walk through what to expect. Visits are short — usually 20 to 30 minutes total.
The skin over the joint is cleaned and numbed with a small amount of local anesthetic. If the joint is swollen, we may draw off a bit of extra fluid first.
The HA is injected into the joint using ultrasound or fluoroscopic guidance to confirm placement. The injection itself usually takes less than a minute.
You'll rest a few minutes, then walk out. If you're doing a weekly series, we'll schedule the next visit before you leave.
Most patients walk out and go about their day. About one in ten experiences a temporary "post-injection flare" — warmth, swelling, and soreness in the joint for one to three days. Ice and acetaminophen (Tylenol) usually handle it. Unlike PRP and BMAC, NSAIDs are fine if you need them.
HA doesn't work right away. Most patients begin to notice less pain and easier movement around the two-to-four-week mark, with the full effect by about six weeks. Benefit averages around six months, though some patients get noticeably longer relief and others get less. If it helps, the injection (or series) can be repeated. If it doesn't, we'll talk about whether to try a different product, move to PRP or BMAC, or consider other options.
HA injections are generally well tolerated. The most common issue is the temporary flare described above. Bleeding and infection are very rare. Allergic reactions are uncommon but possible. Specific risks are reviewed before we proceed.
HA is one of the few knee-osteoarthritis injections insurers often reimburse. KeyTone Medical is out of network with all commercial health insurance plans, so the procedure itself is self-pay — on request we provide a superbill, an itemized and coded receipt, for you to submit to your plan under its out-of-network guidelines. Off-label uses (hip, shoulder, ankle, CMC) are typically not reimbursed at all and are cash-pay. We'll go over cost before scheduling.
No. PRP is made from your own blood and works by delivering growth factors to stimulate healing. HA is a manufactured gel that lubricates and cushions the joint. They work by different mechanisms and have different evidence bases. Sometimes patients benefit from one, sometimes the other, occasionally both at different points.
On average, about six months — but the range is wide. Some patients get a year or more; some get only a couple of months; some don't get meaningful relief at all. If you respond well, the injection or series can be repeated, typically no more often than every six months.
Often, for knee osteoarthritis — when there's imaging consistent with OA and documentation that conservative measures haven't been enough. One thing to know: we're out of network with commercial plans, so reimbursement comes to you through a superbill claim rather than us billing your insurer directly. Off-label uses for hip, shoulder, ankle, or thumb are usually not reimbursed.
The honest answer is that the evidence is genuinely mixed. Some high-quality trials show modest benefit; others show little difference from placebo. Real-world experience is also mixed — some patients clearly benefit, others don't. We'll set realistic expectations and reassess after the first few weeks rather than committing you to repeated injections that aren't helping.
We usually ask you to take it easy for the first 24 to 48 hours — no running, heavy lifting, or high-impact activity — to let the joint settle. After that, normal activity is fine. Continuing with physical therapy and reasonable activity actually helps the injection work.
Authoritative references on this topic, for patients who want to read further. These are educational resources, not medical advice.
Educational information only. This page describes hyaluronic acid injections in general terms. Whether they're appropriate for you depends on your history, exam, imaging, and treatment goals. The risks, benefits, alternatives, and expected results will be discussed in detail at your visit.
