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Achilles tendinopathy is a major cause of prolonged pain and disability in sportspeople and those who undertake an active lifestyle such as hiking and walking. 1- 3 It may cause 2-16% of people to abandon the causative activity. 1, 2, 4, 5 In some settings, 20-30% of patients who present with this condition require surgical treatment. 6- 8 Furthermore, as physical inactivity is a risk factor for many multisystem diseases, 9 Achilles tendinopathy can lead to suboptimal overall health, not just sporting inconvenience.
There have been many studies published on the subject of Achilles tendinopathy, but there remain very few prospective studies of treatment outcome. 4, 10- 13 One factor that limits efficacy studies in Achilles tendon research is the lack of a standardised outcome measure by which to evaluate treatment of Achilles tendinopathy. 14
Several quantitative tests of ankle function 15 have been used to measure outcome in Achilles tendinopathy, 4 and there are tests to evaluate Achilles tendon function after complete rupture. 16 However, condition specific numerical scales generally have greater sensitivity and specificity than general purpose scales. 17- 20 The inventor of the much used Lysholm scale for knee instability emphasised the need for "different or modified scoring systems for the follow-up of patients with different diagnoses". 18 A specific scale for patients with patellar tendinopathy 19 has proved useful in numerous peer reviewed studies. 21- 23 Therefore the aim of this study was to develop and test a questionnaire based instrument to measure the severity of Achilles tendinopathy.
Methods
To develop the questionnaire we performed item generation, item reduction, item scaling, and pretesting as outlined below. We then tested its validity and reliability in clinical and control populations. Ethics approval was obtained from the University of British Columbia ethics committee.
item generation
The Victorian Institute of Sport tendon study group (Melbourne, Australia) first developed an index of severity for patellar tendinopathy. 19 We used this as a template from which to develop a questionnaire specifically for use in Achilles tendinopathy. The literature was reviewed to find items that would be appropriate for inclusion. In addition, colleagues were consulted to find unpublished items used in clinical practice. The second step involved the interview of colleagues with expertise in the area of...