Is Tennis Elbow the Same as Tendonitis?

Tennis elbow is often called a form of tendonitis, but that label is misleading. When researchers examine the tissue involved in chronic tennis elbow under a microscope, they consistently find degeneration rather than the active inflammation that “tendonitis” implies. The distinction matters more than you might expect, because it changes what treatments make sense and what the condition actually needs to heal. Understanding why tennis elbow earned its inflammatory reputation, and why that reputation is outdated, clears up a lot of confusion about the condition.

What Is Actually Happening Inside the Tendon

Tennis elbow, formally called lateral epicondylitis, targets the tendons on the outside of your elbow where the forearm muscles that extend your wrist anchor to bone. The primary tendon involved is the extensor carpi radialis brevis (ECRB), which helps stabilize the wrist during gripping and lifting. For decades, clinicians assumed that overuse caused inflammation in this tendon, so they called it tendonitis and treated it accordingly with anti-inflammatory drugs and ice.

Histological studies have consistently overturned that assumption. When pathologists examine tissue removed from chronic tennis elbow cases, they find collagen degeneration, disorganized tendon fibers, and an increase in immature repair cells rather than the white blood cells you would expect if inflammation were driving the problem. One ultrasound study of 72 patients found the most common appearance was a focal area of abnormal tissue deep within the tendon, which corresponded at surgery to collagen degeneration with fibroblastic proliferation rather than an inflammatory process.¹ The correct description for this type of tissue breakdown is tendinosis, a term that captures degeneration without implying inflammation.²

That does not mean inflammation plays zero role. Early in the injury, or during acute flare-ups, some inflammatory activity likely occurs. Researchers have also identified pain-related neurochemicals like substance P in the tendons of people with chronic tennis elbow, suggesting that the pain signaling system becomes sensitized over time even after any initial inflammation resolves.³ But the dominant process in a tennis elbow case that has been bothering you for weeks or months is failed healing and tissue breakdown, not ongoing inflammation.

Why the Terminology Problem Is Not Just Academic

Calling tennis elbow “tendonitis” steers people toward inflammation-fighting treatments. The logic seems straightforward: if the tendon is inflamed, take something to reduce inflammation. But a Cochrane review looking at the evidence for nonsteroidal anti-inflammatory drugs (NSAIDs) found only limited evidence that topical NSAIDs may help with pain for up to four weeks, and the data had enough methodological problems that firm conclusions could not be drawn.⁴ If the underlying problem were truly inflammatory, you would expect anti-inflammatory drugs to be more convincingly effective.

The preferred umbrella term now is “tendinopathy,” which simply means something is wrong with the tendon without specifying whether it is inflammation, degeneration, or both.² The older labels “tendinitis” and “epicondylitis” persist in medical literature and everyday conversation mostly out of habit. When your doctor says you have tennis elbow tendonitis, they are almost certainly describing the same degenerative condition that researchers now classify as a tendinopathy. The name has not caught up to the science.

Who Gets It and What Puts You at Risk

Despite the name, most people with tennis elbow have never picked up a racket. The condition affects roughly two to three percent of working-age adults, and occupational risk factors are at least as important as recreational ones. A large study of over 3,700 workers found that the prevalence of lateral epicondylitis was about 2.4 percent, and the strongest risk factor was a combination of hard physical exertion with repetitive elbow and wrist movements for more than two hours a day. Among men doing this kind of work, the odds of developing the condition were more than five times higher than among those without those exposures.⁵

Jobs that involve repetitive gripping, twisting, or lifting with the forearm are the main culprits. Think plumbers, electricians, cooks, assembly-line workers, and anyone who spends hours using hand tools. The ECRB tendon is vulnerable because of its anatomy: it generates near-maximal force when the wrist is extended and the forearm is pronated (palm facing down), which is exactly the position many manual tasks demand.⁶ Systematic reviews of work-relatedness have confirmed that physically demanding occupations with repetitive arm movements carry elevated risk.⁷

Age also plays a role. Tennis elbow peaks between the ages of 35 and 55, likely because tendon tissue becomes less resilient and slower to repair over time. There is no strong consensus on whether men or women are more susceptible overall, though the occupational data suggests that the type and intensity of repetitive work matters more than sex.

The Corticosteroid Trap

Corticosteroid injections are one of the most commonly offered treatments for tennis elbow, and the early results look impressive. A randomized trial published in JAMA found that at four weeks, patients who received a corticosteroid injection were dramatically more likely to report improvement than those who received a placebo injection. Pain scores, disability measures, and quality of life all favored the steroid group in the short term.⁸

The one-year follow-up from the same trial tells a different story. At twelve months, the corticosteroid group had lower recovery rates and substantially higher recurrence compared to placebo. Over half of the steroid group experienced recurrence, versus about 12 percent of the placebo group.⁸ A separate study found that when tennis elbow recurred after a steroid injection, patients often perceived more significant pain and disability than they had initially, sometimes leading to additional injections or premature surgery.⁹

This pattern makes more sense once you understand the underlying pathology. If the tendon is degenerating rather than inflaming, a powerful anti-inflammatory might suppress pain signals temporarily without addressing or even worsening the structural problem. The short-term relief can also encourage you to return to aggravating activities before the tendon has had time to remodel, setting up the cycle of recurrence.

Treatments That Address the Actual Problem

Because tennis elbow is fundamentally a failed-healing process, the treatments that work best tend to be those that stimulate tendon repair rather than suppress inflammation. Eccentric exercise, where you slowly lower a weight using the affected wrist, is one of the best-studied approaches. The loading creates a mechanical stimulus that encourages the tendon cells to lay down new, properly organized collagen.¹⁰ It is not a quick fix. You typically need to do these exercises consistently for several weeks before the tendon starts responding, and the initial period can be uncomfortable.

Platelet-rich plasma (PRP) injections have generated substantial interest as an alternative to corticosteroids. The idea is that concentrated platelets from your own blood deliver growth factors directly to the damaged tendon. One randomized trial found that PRP consistently outperformed both glucocorticoid and saline groups on function and disability measures at three and six months.¹¹ Another trial found PRP showed superiority in pain, grip strength, and function scores compared to extracorporeal shock wave therapy and a sham injection.¹²

The PRP picture is not entirely settled, though. A separate randomized controlled trial comparing PRP, corticosteroid, hyaluronic acid, and saline injections found significant improvement in all groups over time, and concluded that none of the injection treatments performed clearly better than placebo at longer follow-up.¹³ That finding raises an uncomfortable possibility: tennis elbow might improve substantially on its own given enough time, and some of what we attribute to treatment effects could be natural recovery. PRP’s advantage may lie in speeding up a process that would happen eventually, rather than producing a uniquely different outcome.

A more unusual approach involves topical nitroglycerin patches applied over the affected tendon. Nitric oxide is thought to support collagen synthesis in the tendon, potentially helping build stronger scar tissue along the lines of stress.¹⁴ Small trials have shown reductions in pain and symptoms with this method.¹⁵ It is not widely adopted yet, partly because of side effects like headaches from the nitroglycerin, but it represents the kind of treatment logic that follows from understanding tennis elbow as a degenerative rather than inflammatory condition.

When It Might Not Be Tennis Elbow

Not all pain on the outer side of the elbow comes from the tendons. Radial tunnel syndrome, a compression of the deep branch of the radial nerve in the forearm, can produce pain in a very similar location. Some researchers have suggested that a proportion of “resistant” tennis elbow cases, those that just do not get better with standard treatment, may actually involve nerve compression rather than or in addition to tendon problems.¹⁶

Distinguishing between the two is genuinely difficult. The definitions, terminology, and clinical tests for radial tunnel syndrome overlap enough with tennis elbow that diagnostic confusion is common even among specialists.¹⁷ One practical clue: if your pain sits slightly further down the forearm from the bony point of the elbow, or if finger and wrist extension against resistance provokes pain more than gripping does, nerve involvement may be worth investigating. This is particularly important if you have been doing all the right things for tendon recovery and seeing no progress.

The Role of Your Brain in Persistent Elbow Pain

Chronic tennis elbow is not purely a tissue problem. A cross-sectional study of people with lateral elbow tendinopathy found that fear-avoidance beliefs and pain catastrophizing were both strongly associated with how intense and persistent the pain was.¹⁸ In plain terms, if you believe that using your arm will cause damage and you avoid all activities because of that belief, the pain tends to be worse and last longer than the tissue damage alone would predict.

This does not mean the pain is imaginary. Neurochemical changes in the tendon and spinal cord, like the substance P accumulation noted earlier, provide a biological basis for amplified pain signaling. But the way you think about and respond to that pain can either help or hinder recovery. Eccentric exercise, for example, works partly by gradually demonstrating to your nervous system that loading the tendon is safe and even beneficial. Avoiding all use of the arm can have the opposite effect, reinforcing the brain’s threat assessment and making the tendon less tolerant of normal loads over time.

Surgery and the Placebo Problem

For the roughly 5 to 10 percent of cases that do not improve with conservative treatment over six to twelve months, surgery becomes a consideration. The standard surgical approach involves identifying and removing the degenerative tissue in the ECRB tendon, either through an open incision or arthroscopically. Arthroscopic approaches allow surgeons to inspect the joint for other problems and may allow more precise removal of the damaged tissue.¹⁹

The evidence for surgery took a humbling turn with a randomized, double-blinded trial that compared real surgical debridement to a sham procedure where everything was identical (anesthesia, incision, postoperative care) except the tendon was not actually treated. Both groups improved substantially in pain, stiffness, grip strength, and functional scores. There was no significant difference between the real surgery and the sham at any time point, including at two and a half years of follow-up.²⁰

This is only one trial, and it does not prove that surgery never helps anyone. But it does suggest that some of the improvement attributed to surgery may come from the postoperative rehabilitation, the forced rest period, or the natural resolution of the condition over time. It also raises questions about how much of any tennis elbow treatment’s benefit, including injections and even exercise, reflects the body’s own healing capacity rather than the specific intervention. For a condition rooted in tissue degeneration, time and gradual reloading may be the most underrated treatment of all.

Nitroglycerin Patches and the Search for Better Options

The idea of slapping a heart-medication patch on your elbow to heal a tendon sounds far-fetched, but it follows logically from the biology. Nitric oxide promotes collagen synthesis, and tendinosis is a collagen problem. Early trials of topical glyceryl trinitrate patches placed over the lateral epicondyle have shown reductions in pain compared with placebo patches, and the theoretical mechanism involves helping the tendon build stronger repair tissue along the lines of stress it actually faces.¹⁵ The practical downsides, mainly headaches and skin irritation from the patch, have kept this approach on the fringes of mainstream practice. But it illustrates how recognizing tennis elbow as a degenerative condition rather than an inflammatory one opens up treatment strategies that would never have been considered under the old “tendonitis” framework.

Tennis elbow, then, is technically not tendonitis, even though the two terms are used interchangeably almost everywhere. The practical lesson is straightforward: if you are dealing with tennis elbow that has lasted more than a few weeks, treatments aimed purely at reducing inflammation are unlikely to solve the problem. Approaches that encourage the tendon to rebuild, whether through controlled loading, growth-factor injections, or simply time and patience, align better with what is actually happening in the tissue.