Achilles tendinopathy is an umbrella term that can encompass both tendinitis and tendinosis. It is also possible (and common) to have co-existing diagnoses; where someone has a degenerative tendon with low grade chronic symptoms, but they turn it into a reactive tendon and re-introduce higher grade symptoms and swelling after an increase in activity. This is also known as an ‘acute-on-chronic’ tendinopathy.
As opposed to tendinitis and tendinosis, which are conditions of the tendon itself, achilles paratenonitis is an acute injury involving inflammation and swelling of the lining of the achilles tendon, also known as the tendon sheath. Typically, there will be high grade pain and significant swelling around the tendon, with a key difference to tendinitis being the presence of crepitus. Crepitus is a creaking or crunching like sensation that can be felt when pointing the foot up and down. The term achilles peritendinitis is also used interchangeably with paratneonitis to describe this condition.
We also need to consider other diagnoses around the achilles tendon, which include; insertional achilles tendinopathy, retrocalcaneal bursitis, subcutaneous calcaneal bursitis, Kager’s fat pad inflammation and plantaris-related achilles pain.