Tendonitis can be classified into three different stages. It starts with acute Achilles tendon pain and if the right steps are not taken to get the tendon back to a healthy state, it progresses. The structure of the tendon weakens over time and can start degenerating and disintegrating. Ultimately leading to an Achilles tendon rupture.
1. Reactive tendonitis (First stage)
The acute phase of Achilles tendonitis (reactive tendonitis) is caused by a change in the amount of work that your Achilles tendon needs to do. Straining, overload and overburdening the Achilles tendon is the biggest deciding factor. Usually, in this phase there will be some inflammation and possibly swelling around the tendon or tendon sheath (synovium).
Let’s say you felt your Achilles ‘pulling’ during a run uphill, but it seems to go away after a while. Now you continue running every day for the rest of the week. At the start of each run you feel pain in your heel, but it improves when you run. It can’t be that bad then, can it? When you push through this pain every time, you are repeatedly causing micro-trauma to your Achilles tendon. If you do not get the right treatment during this phase, the structure of your Achilles tendon starts to change and it gets weaker. At this stage the tendon has the potential to recover and revert back to its normal structure.
2. Tendon dysrepair (Second stage)
Reactive tendonitis (first stage) can progress to tendon dysrepair (second stage) if the tendon is not allowed to recover. During this phase there is continuous breakdown and disorganisation of the collagen network as your body continues to try and heal the tendon. This means that the collagen fibers are not neatly arranged in bundles, but they tear away from each other, like a cable or rope where the individual strands break and seperate. Applying more force will cause more damage.
In this phase, you will feel a dull pain in your heel at the start of your run, but it will linger a little bit longer, and bother you more and more. Now you start to feel the pain not just during your run, but also throughout the day with simple activities like walking or climbing stairs. As the tendon structure changes, it is not capable of doing the work it should and this causes you more pain. If you do not decrease the burden on your Achilles tendon and allow it to rest, further damage will occur and it can now lead to problems elsewhere, like the knee, hip and lower back.
3. Degenerative tendonitis (Final Stage)
Degenerative tendonitis is the final stage and at this stage there is a poor prognosis for the tendon. The degeneration of the tendon are now irreversible. The structure of the Achilles tendon weakens further. Adhesions form between the tendon and the sheath around it. These adhesions are patches of wound tissue that attempts to heal the torn fibers. The adhesions, together with the fact that the tendon thickens, makes the tendon less flexible. The normal gliding movement of the tendon inside the sheath becomes impossible.
Now, the tendon is able to carry even less load. Leaving you in pain with simple daily activities. This phase of tendonitis usually bothers older people who has had underlying and ongoing Achilles tendon problems, or younger people who has continued to overload the tendon.