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What’s the difference between Achilles tendonitis, tendinosis, tendinopathy, and tendinitis?

Updated: May 27, 2023

There is no significant difference between Achilles tendonitis, tendinosis, tendinopathy, and tendinitis. It boils down to a disagreement among researchers – let’s call them Team Tendonitis and Team Tendinopathy. In this article, we’ll explain why researchers propose these different names and why we use tendonitis, tendinosis, tendinopathy, and tendinitis interchangeably. Remember, if you need more help with an Achilles injury, you're welcome to consult one of our team via video call.

What's the difference between tendonitis, tendinitis, tendonosis, tendinosis and tendinopathy?

In this article:

We've also made a video about this:

What tendonitis and tendinitis imply

Medical terms that end in “itis” are used when something is inflamed.

What tendinopathy and tendinosis imply

Medical terms that end in “opathy” or “osis” imply that there is no inflammation and that the condition is mostly caused by degeneration of the tissue, in this case the tendon.

Which of these are correct? It depends on how the tendon pain developed and how long it has been going on for. In overuse injuries, which we mostly treat, there is little or no inflammation most of the time, whereas there is usually inflammation when the tendon pain is caused by something else.

Team tendonitis and tendinitis

What the research shows

In tendon injuries caused by overuse, inflammation is likely only present during the first two or three weeks (reactive stage).

You can also get an acute flare-up on top of a chronic overuse tendon injury, which may mean an increased inflammatory reaction at that point.

Other causes of tendon pain where excessive inflammation is part of the injury process and the main cause of the injury include tendon injuries caused by antibiotics and inflammatory conditions like gout or arthritis.

Team tendinopathy and tendinosis

What the research shows

There is evidence that in cases where tendon pain or injury has been present for more than a few weeks (typically on and off for several months), the structure in that part of the tendon changes. Early studies claimed that there is no inflammation present in those stages but more recent research has shown that perhaps there are some subtle inflammatory actions happening.

Which team are we on?

We don’t care what you call it. Treatment should not be based on whether a condition’s name is followed by “itis” or “osis” or “opathy”! What is important to us is that you assess the person in front of you and create a treatment plan that is best suited to the current state their tendon is in.

The plan should take into consideration:

  • how sensitive the tendon is,

  • how strong it is,

  • what other health issues might be affecting it,

  • what activities a person wants to get back to doing,

  • and what else is going on in their lives that needs to be considered.

So we use the terms tendonitis, tendinitis, tendinosis, and tendinopathy interchangeably so that everyone can understand that the advice we are providing is appropriate for all of these labels.

Don’t let all of this confuse you – the name really doesn’t matter! We’ll mostly be using Achilles tendinosis and tendinopathy, but know that it's exactly the same as Achilles tendonitis or tendinitis for the purposes of how we treat our patients’ Achilles injuries.

How we can help

Need more help with your Achilles injury? You’re welcome to consult one of the team at TMA online via video call for an assessment of your injury and a tailored treatment plan.

Meet the TMA physios

We're all UK Chartered Physiotherapists with Master’s Degrees related to Sports & Exercise Medicine. But at Treat My Achilles we don't just value qualifications; all of us also have a wealth of experience working with athletes across a broad variety of sports, ranging from recreationally active people to professional athletes. You can meet the team here.

Find out how our online service for treating Achilles tendon injuries work.
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About the Author

Maryke Louw is a chartered physiotherapist with more than 15 years' experience and a Master's Degree in Sports Injury Management. Follow her on LinkedIn and ResearchGate.


  1. Cook, J. L., et al. (2016). "Revisiting the continuum model of tendon pathology: what is its merit in clinical practice and research?" British Journal of Sports Medicine 50(19): 1187-1191.

  2. Cook, J. L. and C. R. Purdam (2009). "Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load-induced tendinopathy." British Journal of Sports Medicine 43(6): 409-416.

  3. Dakin, S. G., et al. (2014). "Resolving an inflammatory concept: The importance of inflammation and resolution in tendinopathy." Veterinary Immunology and Immunopathology 158(3): 121-127.

  4. Khan, K. M., Cook, J. L., Kannus, P., Maffulli, N., & Bonar, S. F. (2002). Time to abandon the “tendinitis” myth: painful, overuse tendon conditions have a non-inflammatory pathology.

  5. Scott A, Docking S, Vicenzino B, et alSports and exercise-related tendinopathies: a review of selected topical issues by participants of the second International Scientific Tendinopathy Symposium (ISTS) Vancouver 2012 British Journal of Sports Medicine 2013;47:536-544.

  6. Millar, N. L., et al. (2017). "Inflammatory mechanisms in tendinopathy–towards translation." Nature Reviews Rheumatology 13(2): 110-122.

  7. Scott, A., et al. (2020). "Icon 2019: international scientific tendinopathy symposium consensus: clinical terminology." British Journal of Sports Medicine 54(5): 260-262.


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