A cortisone shot can provide significant short-term pain relief for tendonitis, with studies reporting success rates between 66% and 95% depending on the location and severity. But the relief is temporary, and the injection doesn’t heal the tendon itself. In fact, cortisone may slow the tendon’s natural repair process, which is why it’s typically reserved for cases where rest, ice, and physical therapy haven’t been enough.
How Cortisone Works on Tendon Pain
Cortisone is a synthetic version of cortisol, a hormone your body naturally produces to control inflammation. When injected near an inflamed tendon, it suppresses the inflammatory cascade by reducing the chemical signals that cause swelling, pain, and irritation. Within the first week, it lowers levels of the proteins responsible for triggering inflammation at the site.
Here’s the trade-off: inflammation is also part of how your body repairs damaged tissue. Cortisone disrupts that process. It decreases the activity of cells that break down and rebuild the structural fibers in your tendon, shifts the ratio of strong collagen to weaker collagen, and reduces overall cell survival in the area. Two weeks after exposure, studies have found that tendon cells begin transforming into fat and cartilage cells instead of healthy tendon tissue. So while the pain drops, the tendon’s ability to heal itself is temporarily compromised.
What the Success Rates Look Like
The numbers vary by location. For de Quervain’s tenosynovitis (a common wrist/thumb tendonitis), one study found 84% of patients were completely pain-free at two weeks, with another 8% reporting only mild pain that didn’t limit daily activities. Only about 4% of patients saw no improvement at all. Other studies on the same condition have reported cure rates between 66% and 95%.
For shoulder tendonitis, the picture is more mixed. Cortisone paired with physical therapy tends to produce small to moderate improvements in pain and function in the short term compared to physical therapy alone. But cortisone on its own doesn’t appear to outperform physical therapy in most studies. The injection buys you a window of reduced pain, which can make it easier to do the rehab exercises that actually drive long-term recovery.
How Long the Relief Lasts
Most people notice meaningful pain relief within a few days of the injection, though the first 48 hours can actually feel worse. About 35% of patients experience a post-injection flare, a temporary spike in pain and swelling at the injection site. This flare typically lasts around four days, with a range of one to seven days.
Once the flare subsides, the pain-relieving effects generally peak within the first few weeks. The critical question is what happens after that. At six-month and twelve-month follow-ups, cortisone injections consistently show no advantage over physical therapy alone. The pain relief fades, and without rehab or other treatment addressing the underlying cause, symptoms often return. This is why many clinicians view cortisone as a bridge, not a cure. It reduces pain long enough for you to participate in rehab, strengthen the surrounding muscles, and modify the activity that caused the problem.
Risks Worth Knowing About
The most serious concern is tendon weakening. In a cohort study of patients who received steroid injections for shoulder problems, 9.8% went on to develop a rotator cuff tear, compared to just 1.2% of patients who didn’t receive injections. That’s a meaningful difference, and it’s why repeated injections at the same site raise red flags.
The Achilles tendon carries its own specific risk. Because it bears your full body weight with every step, even a small amount of structural weakening can have serious consequences. Mayo Clinic physicians cite roughly a 2% risk of tendon rupture following a cortisone injection near the Achilles and recommend exploring other options if a first injection doesn’t help.
Other potential side effects include:
- Local tissue thinning: the skin and fat near the injection site can become noticeably thinner or lighter in color
- Post-injection flare: that temporary worsening of pain mentioned above, affecting roughly one in three patients
- Temporary blood sugar elevation: relevant if you have diabetes, as cortisone can raise glucose levels for several days
How Many Injections You Can Get
Clinical guidelines published in the BMJ recommend a maximum of three cortisone injections at any single tendon site. Injections should be spaced at least six weeks apart. If two injections don’t provide at least four weeks of relief each, repeating the injection isn’t recommended, because at that point, the risks of tendon damage outweigh the diminishing benefits.
The American Society of Regional Anesthesia and Pain Medicine published updated guidelines in 2025 noting that clinicians have historically used higher doses than what’s actually needed for effective relief. Lower doses appear to work just as well while reducing exposure to the drug’s negative effects on tissue.
Where Cortisone Fits in Treatment
Cortisone injections aren’t a first-line treatment for tendonitis. They make the most sense after you’ve tried conservative approaches, including rest, activity modification, icing, and physical therapy, for several weeks without adequate improvement. They also make sense when pain is severe enough to prevent you from doing the rehab exercises that would help you recover.
The strongest evidence supports using cortisone alongside physical therapy rather than instead of it. The injection controls pain in the short term while structured exercises rebuild tendon strength and correct the movement patterns that led to the injury. On its own, cortisone provides temporary relief but doesn’t change the long-term outcome compared to doing nothing beyond basic rest.
For weight-bearing tendons like the Achilles or patellar tendon, many clinicians are more cautious and may recommend alternatives like eccentric loading exercises, shockwave therapy, or platelet-rich plasma injections before considering cortisone. The risk-benefit calculation shifts when a weakened tendon could rupture under normal daily stress.