Hyaluronic acid injections in the knee: who they help and for how long

A hyaluronic acid injection temporarily improves the properties of joint fluid and reduces pain in osteoarthritis. It is most often given into the knee, at the early and moderate stage of osteoarthritis. The effect lasts on average seven to eight months and depends on the stage. Hyaluronic acid does not grow cartilage.

What hyaluronic acid is and why it is injected

Hyaluronic acid is a natural component of healthy joint fluid. It gives the fluid its thickness: the joint surfaces glide easily over each other, and impacts are cushioned.

In osteoarthritis the joint fluid becomes thinner and these properties worsen. The idea of the injection is to restore them temporarily. The result can be less pain and easier movement, especially when walking and on stairs.

What osteoarthritis is and how it develops: osteoarthritis.

Who it helps most

Stage	What to expect
Early: joint space slightly narrowed, pain under load	Best result, the effect lasts longest
Moderate: joint space clearly narrowed	Often a good result
End stage: joint space has practically disappeared	Usually a small result
Active inflammation, fluid in the joint	Inflammation has to settle first, then the injection

Hyaluronic acid is most often injected into the knee. For the shoulder, ankle and other joints we decide individually. I have a separate article on the hip joint: injection therapy.

How it is done and what happens next

I give the injection under ultrasound guidance: the screen shows the needle and the joint cavity, so the product goes exactly into the joint and not around it. If there is excess fluid in the joint, I remove it first: the fluid dilutes the product, and its appearance tells us about the cause of the inflammation. More detail: fluid in the joint.

The procedure is done as an outpatient and takes a few minutes. You go home the same day, with advice to reduce load for a while. In the first days, a feeling of fullness in the joint or mild discomfort is common and settles on its own.

The signs that mean you should contact us straight away are different: marked swelling of the joint, redness, fever, or pain that gets worse day by day.

How long the effect lasts

The effect lasts on average seven to eight months. At the early stage it is usually longer, at the later stage shorter.

We do not assess the result the next day: change appears gradually, and the conclusion is drawn after several weeks. If the effect was good, the injection can be repeated when it wears off. If there was almost no effect, there is no point in repeating the same thing, and we think about another path.

What hyaluronic acid cannot do

• it does not grow cartilage or widen the joint space; the same goes for supplements taken by mouth: myth: cartilage regrows with supplements;
• it cannot switch off active inflammation quickly: other methods are used for that, sometimes a steroid injection;
• it cannot replace exercise, weight control and spreading the load correctly.

The injection is part of a complete plan. It gives the best result when the thigh muscles are strengthened and the load on the joint is reduced at the same time. More detail: conservative treatment. On PRP as an alternative: PRP therapy.

If the injection no longer helps

If the effect of hyaluronic acid becomes shorter and shorter, it usually means that the osteoarthritis has progressed. In that case we talk honestly about the next step and look at what has changed on the X-ray.

I do not perform knee replacement: I operate only on the hip joint. If the knee needs surgery, I will refer you to a knee surgeon and give you everything we found at the consultation to take with you. On knee pain in general: knee pain.

Key points

• Hyaluronic acid temporarily improves the properties of joint fluid.
• It gives the best result at the early and moderate stage of osteoarthritis.
• The effect lasts on average seven to eight months, depending on the stage.
• It does not grow cartilage and cannot replace exercise.
• I give the injection under ultrasound guidance.

If your knee or another joint has hurt for more than a week, book a consultation.