Hyaluronic acid injections for osteoarthritis of the knee

This fact box will help you to weigh the benefits and harms of hyaluronic acid injections for osteoarthritis of the knee. The information and numbers are based on the best scientific evidence currently available.

This fact box was developed by the Harding Center for Risk Literacy.

What is osteoarthritis of the knee?

Osteoarthritis is a degenerative disease due to wear and tear of the joint cartilage. Many different factors, such as obesity and strain on the joints, can lead to osteoarthritis of the knee (gonarthrosis). However, the cause is not always clear. At an advanced stage of the disease, joint cartilage and other structures within the joint deteriorate. Consequently, joint pain and stiffness may occur [3].

What are hyaluronic acid injections?

Hyaluronic acid is a substance that is naturally present in the joint fluid. It works in various ways, e.g. by cushioning and lubricating joints [1].

In order to treat osteoarthritis of the knee,industrially produced hyaluronic acid is injected directly into the impaired knee (“intra-articular”) to prevent further degeneration.

Who might consider hyaluronic acid injections?

Adults who suffer from osteoarthritis of the knee can consider hyaluronic acid injections.

Hyaluronic acid injections are currently not covered by statutory health insurance in Germany. Patients have to pay for this treatment because it is considered a non-essential health service.

What are alternative treatment options?

Alternative treatment options include physical therapy, treatment with painkillers, and joint replacement surgery.

Fact box hyaluronic acid injections for osteoarthritis of the knee
Fact box hyaluronic acid injections for osteoarthritis of the knee © Harding Center for Risk Literacy
What does the fact box show?

The fact box shows the benefits and harms of hyaluronic acid injections compared to placebo injections for people with osteoarthritis of the knee.

The table may be read as follows:

The results of existing studies (meta-analyses) are inconsistent regarding the benefits of hyaluronic acid injections. Some studies show benefits in in terms of pain relief and improvement of joint function while others do not. It is hence difficult to definitively assess the benefits. However, two high-quality studies (meta-analyses) indicate that hyaluronic acid injections may lead to a reduction in pain and improvement in function of the knee joint  for up to 26 weeks.

The numbers in the fact box are rounded. The numbers in the benefits section are based on 10 studies with 19,400 participants [1]. The numbers in the harms section are based on 8 studies with about 2,300 participants [2].

What other aspects should be considered?

The studies (meta-analyses) in the systematic review by Campbell et al. (2015) and the studies in each of these meta-analyses differed in many respects: in their measurement instruments, the number of patients included, the length of treatment, and the type of hyaluronic acid injected. Moreover, nothing is known about the long-term effects of the treatment.

Do the results provide proof (evidence) for the benefits and harms of the hyaluronic acid injections?

The study on the benefits is a systematic review of several meta-analyses by Campbell et al. (2015) that analyzed various reviews (meta-analyses) of the benefits and harms of hyaluronic acid injections for osteoarthritis of the knee.The quality of the meta-analyses considered in the review are inconsistent and the results partly contradictory. Nevertheless, the results should not be discounted because the conclusions are based on two high-quality meta-analyses.

What does this mean?

The meta-analyses included in the systematic review are of moderate quality. None of the meta-analyses had serious deficits that might have biased the results. Thus, there are indications that hyaluronic acid injections might be beneficial. Further research on the basis of studies with high levels of evidence (I and II) is necessary in order to obtain conclusive results.

Version history of the fact box
  • December 2016 (last update)

Information within the fact box was obtained from the following sources:

[1] Campbell KA, Erickson BJ, Saltzman BM, et al. Is local viscosupplementation injection clinically superior to other therapies in the treatment of osteoarthritis of the knee: A systematic review of overlapping meta-analyses. Arthroscopy 2015;31(10):2036-45.e14. doi: 10.1016/j.arthro.2015.03.030.

[2] Trojian TH, Concoff AL, Joy SM, et al. AMSSM scientific statement concerning viscosupplementation injections for knee osteoarthritis: importance for individual patient outcomes. Br J Sports Med 2016;50(2):84-92. doi: 10.1136/bjsports-2015-095683.

[3] Jüni P, Hari R, Rutjes AWS, et al. Intra-articular corticosteroid for knee osteoarthritis. Cochrane Database Syst Rev 2015(10) doi: 10.1002/14651858.CD005328.pub3.

Documentation on how the numbers in the fact box were determined is available on request.