Diagnosis is based on the clinical features of the disease, with the location of the pain as an important discriminating factor. The spot of maximum pain and painful swelling in MPAT is located 2 to 6 cm proximal to the insertion, whereas in case of insertional Achilles tendinopathy, the spot of maximum pain is at the tendon-bone junction. Symptoms can be exacerbated when getting up after a period of rest. In isolated paratendinopathy, there is a local thickening of the paratenon, and the area of swelling does not move with dorsiflexion and plantarflexion of the ankle. In contrast, the area of swelling moves with dorsiflexion and plantarflexion of the ankle in case of isolated tendinopathy. Diagnostic imaging should be considered to rule out other causes of Achilles tendon pain or to establish the diagnosis of MPAT when in doubt.

As in the case of insertional Achilles tendinopathy, the aetiology of MPAT is likely multifactorial and may include advanced age, obesity, hypertension, diabetes, and steroid use, to mention only a few. Particularly in athletes, the onset of MPAT may also be influenced by poor training habits including excessive training, training on hard or sloping surfaces, and abrupt changes in scheduling.

It has been hypothesized that the healing of injuries of the Achilles tendon as a result of overuse involves the penetration of small blood vessels from the paratenon into the tendon in order to increase healing by providing improved blood flow. However, these small blood vessels are accompanied by small nerve fibres with high concentrations of nociceptive substances including glutamate, substance P, and calcitonin gene-related peptide (CGRP). Those small nerve fibres are considered the cause of pain in chronic MPAT.