Prevalence

Injury to the TA is very common among a variety of populations, from elite athletes to mostly sedentary individuals. As with many injuries of this aetiology, they present more commonly among the athletic population than in inactive people, and it has been reported that athletes are at up to thirty times greater risk of developing Achilles Tendinopathy (AT) than their sedentary counterparts (Brukner & Kahn, 2007).
AT has been reported most commonly among individuals who participate in middle and long-distance running, tennis, badminton, volleyball, track and field, and soccer (Paavola et al, 2002).
Siobhani et al (2013) investigated the prevalence of AT in ballet dancers, and found it to be up to 338.5/1000.
Conflicting reports of prevalence have been reported in runners, both elite and amateur. It is accepted that incidences are increased in those who regularly run, though the numbers vary. Reports of between 25% and 50% are common in the literature (Siobhani et al, 2013; Abate et al, 2012; Gaida et al, 2010; Kraemer at, 2012; Fredburg & Stengaard-Pederson, 2008).
Kraemer et al (2012) reported AT as the second most common overuse/chronic injury in rugby players, only behind chronic lateral ankle instability.
Similar to that in ballet dancers, Joseph et al (2012) reported a lifetime prevalence of AT in male gymnasts at approximately 40%.
In a study of elite professional footballers across Europe, Gajhede-Knudsen et al (2013) reported that 2.5% of all injuries sustained by soccer players were AT.
The reported prevalence of AT in the sedentary population varies within a limited range throughout the literature, thus suggesting consistency of the findings. Authors claim that the prevalence of the condition is between 5.9%-10% (Fredburg & Stengaard-Pederson, 2008; de Jonge et al, 2011; Gaida et al, 2010; Abate et al, 2012).
Another interesting finding in the literature is the presence of AT related changes in asymptomatic tendons. Gaida et al (2010) found that approximately 13% of asymptomatic runners had evident pathology under ultrasound investigation. Joseph et al (2012) described more modest findings in a non-athletic population, suggesting that 3.8% of people had sub-clinical degenerative changes in the TA. Contrary to these, other findings show much more significant incidences of asymptomatic degeneration in tendons, with Joseph et al (2012) describing sub-clinical changes in up to 40% of male gymnasts. The investigations by Magnan et al (2014) suggested similar levels to this in runners, with 34% of people without pain showing ultrasonographic changes.
The incidence of AT has been reported as high in middle to long distance runners, however in a study of former elite athletes in Finland, Kujala et al (2005) found that sprinters more commonly suffered from TA ruptures that tendinopathy.
Across the literature it is reported that up to 30% of those who suffer AT have bilateral symptoms (Öhberg & Alfredson, 2004), and that over 40% of patients develop symptoms on the contralateral side, up to 8 years after the initial appearance of AT (Paavola et al., 2000).
AT has been most commonly reported in individuals between the ages of 30-60 years, and in recent years there has been no distinction between the prevalence in men and women (Paavola et al, 2002; Gravare Sibernagel, 2006; Longo et al, 2009).
As the presence of AT is a clinical diagnosis using subjective and objective assessment, the presence of ultrasonographic changes has been shown to have limited correlation with diagnosis. In a study by Comin et al (2013), the presence of sonographic abnormalities was common in ballet dancers, but only the presence of hypoechoic changes was predictive of future tendon pathology. Thus the presence of abnormalities detected using ultrasound imaging cannot constitute prevalence rates (Boesen et al, 2011).