This guide summarizes evidence on the effectiveness and safety of three treatments for osteoarthritis of the knee: use of the supplements glucosamine, chondroitin, or both combined; viscosupplementation (injection of hyaluronan into the knee); and arthroscopic lavage and debridement of the knee joint. The evidence evaluated comes primarily from comparisons of each treatment approach with a placebo. This guide does not address other treatments, such as exercise, physical therapy, pain medications, corticosteroid injections, or knee replacement.

Clinical Issue

Osteoarthritis (OA) is the most common form of chronic arthritis worldwide and is a key cause of pain and disability in older adults. In the United States, clinically significant disease affects 10–20 percent of individuals age 60 and over. Osteoarthritis of the knee, about twice as common as OA of the hip, is becoming an increasingly important condition with the aging of the U.S. population.

Osteoarthritis risk factors include injury, prior joint inflammation, abnormalities of joint shape, and obesity. The natural history of knee OA and the factors leading to its progression are not fully understood.

The goals of treatment are to reduce pain and improve joint function. Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used as first-line treatment for OA pain, along with exercise and weight loss. The treatments described in this guide are intended to promote healing of damaged cartilage in the knee or to augment the composition of synovial fluid.

Clinical Bottom Line

For people with osteoarthritis of the knee, the following treatments do not lead to clinically meaningful improvement.

• Glucosamine hydrochloride and chondroitin sulfate
  LEVEL OF EVIDENCE:
• Viscosupplementation (intra-articular injection of hyaluronan products)
  LEVEL OF EVIDENCE:
• Arthroscopic lavage with or without debridement
  LEVEL OF EVIDENCE:

Glucosamine and Chondroitin

The dietary supplements glucosamine and chondroitin have been advocated as treatments for osteoarthritis pain based on the theory that they may increase the rate of new cartilage formation. Glucosamine is a precursor to glycosaminoglycan, which is believed to play a role in the growth of cartilage and its repair. Chondroitin is part of a large proteoglycan molecule that gives cartilage flexibility and is thought to inhibit enzymes that break down cartilage.

Both substances are found naturally, and supplements are made from animal tissue. Chondroitin sulfate is purified from animal cartilage, such as cartilage from cows or sharks. Glucosamine comes from the shells of crabs, lobsters, or shrimp.

They are both sold over the counter as oral supplements. Supplements are not subject to review or approval by the U.S. Food and Drug Administration and are not standardized. As such, the amount of active ingredients or possible contaminants may vary among products. Glucosamine is available in different forms, most commonly glucosamine sulfate or glucosamine hydrochloride.

Viscosupplementation

Synovial fluid serves as a shock absorber to reduce friction from joint motion. Hyaluronic acid is a naturally occurring substance found in synovial fluid. As cartilage wears down in osteoarthritis, the level of hyaluronic acid in the joint also decreases.

The intra-articular injection of hyaluronan, known as viscosupplementation, is believed to improve the elastoviscosity of the arthritic joint by increasing the hyaluronic acid concentration. In clinical practice, hyaluronan injections are performed in an effort to reduce pain and improve function. The clinician enters the joint space with a needle, injecting a small amount of hyaluronan product (2.5–5 cc of solution). The procedure is repeated from three to five times over a period of several weeks.

Arthroscopic Surgery for Osteoarthritis

Arthroscopic surgery allows a surgeon to visualize the interior joint space. The procedure provides access to the joint for lavage, using saline irrigation to remove particulate material, such as cartilage fragments and calcium crystals. Arthroscopy also allows for debridement, whereby surgical instruments are used to smooth any rough articular surfaces. The goals of arthroscopic lavage and debridement are to decrease synovitis and improve joint motion.

Other Options

The available research has found none of the treatments reviewed in this guide to be effective for the general population of people with knee osteoarthritis. Thus, clinicians may need to consider other treatments.

AHRQ has released a separate guide for clinicians on non-narcotic pain medications for osteoarthritis, available at www.effectivehealthcare.ahrq.gov. Analgesic medicines provide pain relief and may allow people to improve their activity levels. Other approaches, such as exercise and weight loss, can relieve knee symptoms and offer other health benefits as well.

For some people with severe osteoarthritis, total knee replacement may relieve symptoms and improve function. It is important to consider the potential risks and benefits of this surgical procedure. AHRQ has published an evidence report on total knee replacement that is available on the AHRQ Web site: www.ahrq.gov/clinic/tp/kneetp.htm.

Resources for Patients

Osteoarthritis of the Knee: A Guide for Adults is a companion to this Clinician’s Guide. It can help people develop strategies for managing knee osteoarthritis. It provides information about glucosamine/chondroitin, viscosupplementation, and arthroscopic surgery, as well as general self-help approaches.

Choosing Pain Medicine for Osteoarthritis: A Guide for Consumers provides information about both prescription and over-the-counter non-narcotic analgesic medications, including NSAIDs.

For More Information

For electronic copies of the consumer guides, this clinician’s guide, and the full systematic review, visit this Web site: www.effectivehealthcare.ahrq.gov

For free print copies, call:

The AHRQ Publications Clearinghouse

(800) 358-9295

Consumer’s Guide, AHRQ Pub. No. 09-EHC001-A

Clinician’s Guide, AHRQ Pub. No. 09-EHC001-3

Source

The source material for this guide is a systematic review of 86 research publications. The review, Treatment of Primary and Secondary Osteoarthritis of the Knee (2008), was prepared by Blue Cross and Blue Shield Association Technology Evaluation Center Evidence-based Practice Center. The Agency for Healthcare Research and Quality (AHRQ) funded the systematic review and this guide. The guide was developed using feedback from clinicians who reviewed preliminary drafts. The full systematic review is available at www.effectivehealthcare.ahrq.gov.

AHRQ created the John M. Eisenberg Center at Oregon Health & Science University to make research useful for decisionmakers. This guide was written by Susan Woods, M.D., Erin Davis, B.A., Martha Schechtel, R.N., Valerie King, M.D., and David Hickam, M.D., of the Eisenberg Center.