In general, the development of hyaluronate sodium for knee osteoarthritis dates back to the early to mid 1990’s. The full mechanism on how these compounds work has not been fully understood, but it is believed that they stimulate the cells in the joints to produce joint fluid and thus provide lubrication and cushioning within the joint. In the United States, these compounds have only been FDA approved for the use in the knee joint, but around the world they have been used successfully in a number of joints including shoulders, hands, hips and feet.
Knee Joint Injections
The first compound used was Synvisc. This has been produced from the rooster combs (the flesh on the top of their head) and was highly refined. Initially, it was administered in a series of five injections and has gradually been changed to a single injection. Orthopedic knee surgeons were the first to perform such injections and still probably perform the most of these injections. Since it was the first product on the market, many physicians are likely to use it.
From experience, however, it has significant drawbacks. The number one is that since it is refined from an animal product, there is a definite significant percentage of people who will have an acute inflammatory reaction to this injection. The reaction in the joint is not distinguishable from a joint infection and does often require further intervention, from checking the patient for infection, aspirating the joint, possible hospitalization, and further injection of the joint with steroid.
Since the early 2000’s, artificial hyaluronate sodium compounds have been genetically engineered and are absolutely pure compounds without any material that could cause an allergic response. All these compounds are somewhat similar and have similar effectiveness. Again, initially they came in a series of five injections, but they then refined it to a series of three injections, and now some are a single dose injection. The effectiveness in a variety of studies ranges for reducing knee pain from about 10 percent of people to 30 percent and a maximum of up to 50 percent. Injections often have to be repeated every six months to be most effective.
Who Would Benefit From Knee Injections?
The indications for these injections are osteoarthritis of the knee. Patient selection includes those who cannot take NSAID medications like ibuprofen, those who have not had long relief with steroid joint injections or are limited with steroid use, and those who have mild to moderated degenerative changes to the joint.
Once a patient is found to be a candidate for hyaluronate sodium joint injections, product selection is the next issue. In reality, this is the grey zone for recommendations, and experience with these products is helpful. Manufacturers of the products are pushing the single dose compounds, which these are convenient, however from providers it seems these may be somewhat less effective at producing results than those that are a series of three injections. Again, patient selection may be the most important factor but this is hard to tell definitively. The products that are a series of five injections do not seem to work better than those that are three injections. Further, none of the products are really better than the others when they are genetically engineered pure chemicals.
Choosing the hyaluronate sodium products for injection is based now on several practical issues. The first is to choose an artificial product that is pure. From personal experience, it is a nightmare to deal with an inflammatory reaction to one of these products and the only one that has this issue has been Synvisc, and you’d be best to avoid this injection unless you have a very experienced orthopedic surgeon who can assess your risk of a bad reaction. The best results are from genetically engineered pure products that are a series of three injections, since these tend to induce the cells in the knee to produce joint fluid on their own.
Single shot products may not be as good at inducing the knee cells to produce lubrication from a technical standpoint. The choices then are from three products that include Hyalgan, Euflexxa, and Supartz. These should all produce relatively equal results for the patients, but again on average if the knee osteoarthritis is not extreme, relief in about 30 to 50 percent of the patients is expected. All these products are FDA approved for the knee and the services to provide injections are usually covered by all insurances and are not considered experimental.
The last selection criterion is based on product cost and if an insurance carrier has a specific drug preference. The recommendation for a hyaluronate sodium supplementation product therefore would be one of the three products that include Hyalgan, Euflexxa, or Supartz unless the insurance carrier requires a single shot product, either Orthovisc or Monovisc.
Beyond the above discussion, all these injections should be done with some type of visualization procedure, either fluoroscopy or ultrasound to prove needle location and delivery to the joint space. Secondly, for those patients who want the state of the art treatment and who can pay cash, studies indicate that PRP injections have about a 50 percent success rate for pain relief for at least six months at a time. Furthermore, for the cash paying clientele, they can also use hyaluronate products as well as PRP in many of the joints in the body with about a 50% percent success rate.
Thomas Cohn, MD
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