Corticosteroid - or more commonly called “cortisone” - injections are routinely performed in medical offices throughout the world. Injections for the knee have been described as far back as 1897, but it really wasn’t until the 1960s that knee injections of steroids became widely available. Over the last 50 yeas, thousands of papers have been dedicated to corticosteroid injections of the knees but not many of them can stand up to rigorous scientific analysis. Furthermore, the use of steroid injections have been extrapolated to other joints and tendons in the body, but the truth is, the value and effect of injections in these areas may be even less understood and scientifically proven.
If we were to zoom down into cells we would see complex shaped protein molecules that acct as landing sites, or “receptors” for steroids. When a steroid chemical binds to one of these receptors they can affect hormone or gene expression. As scientists, we know that corticosteroids have both anti-inflammatory and immunologic effects, but their mechanism of action are complex and not completely understood. There are a handful of studies of cortisone injections in the knee for arthritis which show fleeting effects of pain relief, but its unclear exactly how or why this commonly used medication actually helps.
Typical arthritis is a gradual loss of cartilage from the ends of the bones. You can see the pearly white cartilage if you ever pick up a chicken bone and look at its end. This cartilage helps to absorb and distribute pressure within our joints. Over the years from injuries or wear and tear, and also likely from genetics, cartilage in the knee can become thinner and thinner until the bones of the knee are touching each other. This increase stress on the cartilage-less bone can cause pain and some inflammation, but arthritis really isn’t an inflammatory condition, so it doesn’t make complete sense why a corticosteroid can help. There is no doubt that it can provide some relief, usually just a few weeks, but if you ask doctors, patient responses are variable. Some patients swear by their annual or semi-annual injection cortisone injections while others will tell you they maybe only had one or two days of relief and then the pain came back. Unfortunately, this unpredictable response is even less predictable when it comes to treating non-arthritis conditions of the knee such as tears of the ligaments, tendons, or other structures.
When it comes to corticosteroid injections, especially in the world of orthopedics, you will find surgeons who inject everyone, only older patients or specific diagnoses, or sometimes nobody at all. Those surgeons who inject everyone have several beliefs among which include that cortisone is rather harmless, it is effective, and if it doesn’t work then there is always surgery. Those who avoid it altogether point to the potential risks and instead lead patients towards less-studied, but possibly superior alternatives such as Platelet-Rich-Plasma (PRP) or stem cells. These are promising options, but the verdict is still out on their long-term efficacy and unlike cortisone, they are not covered by insurance and run anywhere from 500 to 2,000 dollars an injection. In addition, injections that mimic the lubrication fluid of the knee have been shown to be more effective and longer lasting than cortisone, but due to some conflicting earlier studies, many national medical specialty groups cannot fully recommend them and insurances are starting to approve them less often for the knee, and won’t even consider it for other joints in the body. Some doctors adopt the belief that there may be a risk to the cartilage with cortisone and therefore will limit their injections only to those who already have evidence of arthritis with the belief that the die has already been cast when it comes to the status of the cartilage in the knee.
Geography of patient demand may also play a role. For example, a surgeon in the Midwest may see a farmer who only wants to come to the doctor for a knee injection once or twice a year and has no interest in traveling to get an MRI or weekly Physical Therapy visits. Or in Southern California, a 49 year-old semi-professional volleyball player may want an injection before an upcoming tournament since that is what he or she has been doing for years and is convinced their performance is not limited by pain because of the effects of the injection. Injection patterns also vary from the private practice to the academic setting where financial considerations and reimbursements differ. In private practice, increased overhead and decreased reimbursement from insurance companies may force physicians to rely on cortisone injections as a significant source of revenue, which is further bolstered with the use of ultrasound that helps the surgeon locate more specifically where the injection is going.
When we look at the basic science studies of corticosteroids in the laboratory, we know that cortisone injections have an effect on the health of cartilage. There is a time- and dose-dependent effect of corticosteroids. Beneficial effects of corticosteroids occur at low doses and short exposure times where there may actually be increased cell growth and recovery from damage. However, at higher doses and longer exposure times, corticosteroids can be associated with cartilage damage. The scientific evidence in treating other conditions of the body which are commonly injected is even less convincing. Perhaps the two most injected areas of the body that have the least supporting evidence are the rotator cuff of the shoulder and the tendons of the elbow. Just to clarify, as muscles insert into bones, they become thick tendons as opposed to the meaty substance of the muscles so they can make bone and joints move. This is in contrast to ligaments which are thick bands that simply connect one bone to another without moving anything.
The rotator cuff is a group of tendons that help rotate you shoulder internally and externally and also help you to start raising your arm out at the side. When these tendons become injured or over-used they can become inflamed and the covering over them called the bursa can also get inflamed leading to a condition called “bursitis” or inflammation aka “itis” of the bursa. In order to reduce this inflammation, doctors often inject cortisone into the bursa of the shoulder. Unfortunately, the overall effects of injection in the tendons aren’t fully understood and recent studies of the effects of cortisone on rotator cuff tendons in rats have shown decreases in tendon strength after only a single injection. Repeated corticosteroid injections are especially worse.
When it comes to cortisone injections for inflammation of the tendons on the outside of the elbow, a condition commonly referred to as “tennis elbow”, the results are also mixed. There is no doubt that patients can experience relief with corticosteroid injections, but some controversy has been raised due to the fact that some studies have shown that patients who received cortisone shots had a much lower rate of full recovery than those who did nothing or who underwent physical therapy. They also had a higher risk of relapse than people who adopted a more conservative approach. That being said, many patients are too busy and active to adopt a more complacent wait-and-see approach and are seeking a more immediate solution to their pain by visiting their doctor. To them, simply being told to wait it out after making an appointment and paying a copay seems like a waste of time.
To complicate matters, many studies show that the pain affecting these tendons or bursa, i.e. the "itis", may not actually be inflammation. Tennis elbow for example actually shows less evidence of inflammation and more evidence of blood vessel invasion and tissue degeneration and disarray. So the question then becomes why do these injections work? Some scientists think there is an effect on the nerve receptors involved in creating the pain in the sore tendons. They act to change the biology of pain in the short term. This why corticosteroid injections may be actually helpful for the acute inflammatory-type pain but don't actually do anything to cure the disease. In some cases like rotator cuff bursitis where the tendons are pinched under the top of a forward leaning shoulder blade, physical therapy to re-train the shoulder blade to get it out of the way as the arm is raised is really the long-term solution to the problem and the role of the injection may be to help the patient find short-term pain relief to be able to do the therapy.
As a profession, orthopedics and other medical specialties are continuing to reappraise what we have been doing for decades to see if the evidence actually shows what we are doing is helping the patient, or if what we are doing is only useful in the short-term with other therapies perhaps better in the long-term. That is why there is a quest underway for better and longer-lasting therapies but as medical professionals and scientists, we must be careful to continue to self-reflect and see what the evidence of efficacy actually tells us.