Diagnosing Achilles tendinopathy is like delicious spaghetti carbonara: it is all about key ingredients, but not all chefs use the same recipe.

Achilles tendinopathy is the term used to describe the clinical entity of localised Achilles tendon pain that is associated with load-bearing activities. Achilles tendinopathy as a term was agreed on the 2018 International Scientific Tendinopathy Symposium Consensus (ICON) statement—which followed an expert meeting in Groningen (the Netherlands).1 Having uniform terminology is important for many reasons. But a clinical term is not the same as a diagnosis with clear diagnostic criteria. Clear diagnostic criteria help patients understand their problem, guide treatment and determine prognosis. Naming a medical condition can be likened to naming a recipe, but the exact ingredients used can differ between chefs. In this editorial, we discuss the diagnostic challenges, where ‘top chefs’ disagree which ingredients are present in mid-portion Achilles tendinopathy.

The paradigm shift in diagnosing injuries in sports medicine

Many medical diagnostic tests are often validated by comparing them to a gold standard (eg, imaging, surgical or histological findings). Most sports injuries and long-standing musculoskeletal pain conditions have unclear pathogenesis and lack clear gold standards (consider patellofemoral pain). When imaging was added to the clinical diagnostic criteria in patients with patellofemoral pain it added no value.2 The classic tissue-based diagnosis paradigm has been increasingly abandoned. A paradigm shift towards using history and clinical examination as the cornerstones in the diagnostic process has occurred. Could this work in Achilles tendinopathy?

Clinical diagnostic criteria: which ingredients are needed for Achilles tendinopathy?

Patient history is incontrovertibly an essential ingredient to diagnose Achilles tendinopathy—patients must have Achilles tendon pain, which worsens on loading.1 Also, patients can point to whether their pain is localised to the Achilles tendon. On examination, physicians can assess localised tendon thickening with tenderness (pain on palpation). These three clinical findings are simple and can be assessed reliably3—but are all three of them essential ingredients to diagnose Achilles tendinopathy?

What do top chefs say?

Let’s examine which diagnostic criteria expert researchers use. Do their Achilles tendinopathy cookbooks all use the same ingredients? Our recent review with network meta-analysis on treatments for mid-portion Achilles tendinopathy4 extracted diagnostic criteria from 25 randomised controlled trials. Localised Achilles tenderness, localised tendon thickening and pain associated with load-bearing activities were the most commonly used ingredients (figure 1). When all three clinical diagnostic elements are present, the clinical diagnosis seems straightforward—just like if one is presented with a traditional carbonara. But there are less straightforward clinical cases, like when the tendon is painful but there is no thickening. This is where it becomes a challenge to define the point at which the condition is deemed to be present. There is spaghetti, egg and bacon, but no parmesan—is it still carbonara? It may well be that there are variations within the recipe (ie, subclassifications) but it would be great if chefs could agree on this.

Figure 1

Extracted criteria used for the diagnosis in the randomised trials for mid-portion Achilles tendinopathy (n=25). The displayed signs and symptoms are located to the Achilles tendon mid-portion or are a result of pain in this area. VISA-A; Victorian Institute of Sport Assessment—Achilles. VAS; Visual Analogue Scale.

Should imaging be part of the recipe?

Imaging might be useful, especially in challenging cases where not all clinical diagnostic criteria are present. It can depict characteristic changes for tendinopathy: increased tendon thickness, abnormal tendon structure and increased vascularity. A major drawback of imaging is that ‘abnormal’ findings (also referred to as ‘morphological changes’) are present in 25% of asymptomatic Achilles tendons.5 A similar problem is present in other musculoskeletal disorders, such as osteoarthritis.6

How do expert chefs feel about imaging? The majority (74%) of the ICON participants felt that imaging was not an essential ingredient for diagnosing Achilles tendinopathy.1 Yet more than half (55%) of the randomised studies we reviewed4 used imaging in the diagnostic process. It is clear that top chefs do not all agree on the need for imaging!

Is a pathological tendon a vital ingredient to diagnose Achilles tendinopathy?

A recipe where the patient has localised Achilles tenderness and a normal imaging appearance is another challenging case. Is that Achilles tendinopathy? Cook and Purdam’s proposed continuum model of pathology proposes a potential sequence of changes.7 Increased tendon cell proliferation and glycosaminoglycans with well-arranged tendon fibres are the features of early reactive tendinopathy. These findings cannot be detected using conventional ultrasound or MRI. While the presence of pathological changes in that situation cannot be confirmed with current method, that phenomenon (localised tenderness with ‘normal’ imaging) may be a subcategory of Achilles tendinopathy (early stage tendinopathy—preimaging). This opens the discussion whether we should consider tendinopathy as a clinical entity (like patellofemoral pain) or as a continuum with specific progressive pathology (like osteoarthritis, which uses the Kellgren and Lawrence Scale to classify the radiological severity of the disease). Should we distinguish different subclassifications of Achilles tendinopathy?

Can we agree on the exact recipe(s) for Achilles tendinopathy?

It is hard to define the exact ingredients needed to diagnose Achilles tendinopathy. How can we improve our diagnostic recipe(s)? The ICON meetings, where lots of top chefs attend, could be an appropriate platform to initiate a new widely supported agreement on diagnostic criteria for Achilles tendinopathy. Uniform diagnostic recipes on when to diagnose Achilles tendinopathy would be a great start.8 Identifying possible subclassifications, based on certain diagnostic ingredients, has several possible advantages: improving tailored individual treatments or better inform us a patient’s prognosis.9