The clinical diagnosis of Achilles tendinopathy: a scoping review

Background Achilles tendinopathy describes the clinical presentation of pain localised to the Achilles tendon and associated loss of function with tendon loading activities. However, clinicians display differing approaches to the diagnosis of Achilles tendinopathy due to inconsistency in the clinical terminology, an evolving understanding of the pathophysiology, and the lack of consensus on clinical tests which could be considered the gold standard for diagnosing Achilles tendinopathy. The primary aim of this scoping review is to provide a method for clinically diagnosing Achilles tendinopathy that aligns with the nine core health domains. Methodology A scoping review was conducted to synthesise available evidence on the clinical diagnosis and clinical outcome measures of Achilles tendinopathy. Extracted data included author, year of publication, participant characteristics, methods for diagnosing Achilles tendinopathy and outcome measures. Results A total of 159 articles were included in this scoping review. The most commonly used subjective measure was self-reported location of pain, while additional measures included pain with tendon loading activity, duration of symptoms and tendon stiffness. The most commonly identified objective clinical test for Achilles tendinopathy was tendon palpation (including pain on palpation, localised tendon thickening or localised swelling). Further objective tests used to assess Achilles tendinopathy included tendon pain during loading activities (single-leg heel raises and hopping) and the Royal London Hospital Test and the Painful Arc Sign. The VISA-A questionnaire as the most commonly used outcome measure to monitor Achilles tendinopathy. However, psychological factors (PES, TKS and PCS) and overall quality of life (SF-12, SF-36 and EQ-5D-5L) were less frequently measured. Conclusions There is significant variation in the methodology and outcome measures used to diagnose Achilles tendinopathy. A method for diagnosing Achilles tendinopathy is proposed, that includes both results from the scoping review and recent recommendations for reporting results in tendinopathy.


INTRODUCTION
Achilles tendinopathy describes the clinical presentation of pain localised to the Achilles tendon and associated loss of function with tendon loading activities (De Vos et al., 2021;Millar et al., 2021). However, clinicians display differing approaches to the diagnosis of Achilles tendinopathy due to inconsistency in the clinical terminology, an evolving understanding of the pathophysiology, and the lack of consensus on clinical tests which could be considered the gold standard for diagnosing Achilles tendinopthy (De Vos et al., 2021;Millar et al., 2021;Docking, Ooi & Connell, 2015;Cook et al., 2016). Conversely, when describing the clinical condition of persistent pain and dysfunction of the Achilles tendon in relation to mechanical loading, consensus agreement has identified the preferred terminology to be 'tendinopathy' rather than other common terms such as 'tendinitis' and 'tendinosis' . However, the consensus agreement for terminology does not provide a clear criteria with which to diagnose Achilles tendinopathy (De Vos et al., 2021).
Additionally, when considering the diagnosis of Achilles tendinopathy, distinctions can be made between the diagnosis of tendinopathy and clinical diagnosis of Achilles tendinopathy. As described by Aggarwal et al. (2015), a diagnosis is based off a broad set of signs and symptoms to reflect all the potential features and severity of a pathology. Whereas, a clinical diagnosis of Achilles tendinopathy requires a specific set of signs, symptoms and tests to define a homogenous group of patients across studies and geographical regions (Aggarwal et al., 2015). In the case of Achilles tendinopathy, the diagnosis of Achilles tendinopathy is determined by the presentation of pain localised to the Achilles tendon and associated loss of function with tendon loading activities (De Vos et al., 2021;Millar et al., 2021). However, this broad description may include other pathological disease processes such as retrocalcaneal bursitis, complete or partial rupture of the Achilles, tarsal tunnel syndrome, neuroma/neuritis of the sural nerve, rupture posterior tibial tendon, or arthritic conditions of the ankle that need to be differentially diagnosed . Thus, it becomes relevant to understand the process to determine a clinical diagnosis of Achilles tendinopathy.
The clinical diagnosis of Achilles tendinopathy is predominantly derived from patient history, patient reported load related pain, and pain provocation tests . Patient history, localised Achilles tendon pain and pain on palpation are considered key to diagnosing Achilles tendinopathy (De Vos et al., 2021;Millar et al., 2021) and can all be assessed reliably . Additional pain provoking tests; such as the single leg heel raise, hop test, Royal London Hospital Test or Painful Arc Sign; have been suggested as useful to confirm a clinical diagnosis of Achilles tendinopathy Reiman et al., 2014). However, many leading researchers disagree on the which clinical tests are essential to diagnose Achilles tendinopathy (De Vos et al., 2021). Conversely, it is agreed that uniform diagnostic criteria would be useful in identifying possible subclassifications of Achilles tendinopathy and thus improving tailored individual treatment programmes or monitoring patient progress (De Vos et al., 2021). Table 1 The nine core health domains of tendinopathy as recommended by Vicenzino et al. (2020).

Domain Description Example
Patient rating of overall condition A single assessment numerical evaluation 0-100% Pain on activity or loading Patient reported intensity of pain during a tendon loading activity. VAS, NRS Participation Patient rating of participation levels in sport or engagement across other areas. Tegner Activity Scale Function Patient rating of function and not referring to the intensity of their pain.

Patient Specific Function Scale
Psychological factors Patient rating of psychological impact (e.g. Pain self efficacy, kinesiophobia, catastrophisation) . PCS Disability Scores from a combination of patient rated pain and disability due to pain in relation to tendon specific loading activities VISA-A Physical function capacity The quantitative measures of physical tasks such as number of hops, number of squats and dynamometry.
Single leg heel raise Quality of life Patient rating of general wellbeing EQ-5D Pain over a specified time Patient reported intensity of pain over a specified time period (e.g. morning, night, 24 h).
of the topic, a scoping review was used to facilitate the collection and charting of evidence with the aim of identifying key themes, knowledge gaps and types of evidence currently available. Figure 1 provides an overview of the overall study design and process to answer the primary aim and specific objectives.

Search strategy
A single researcher (WM) completed a literature search to identify, screen and select studies in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis Extension for Scoping Reviews (PRISMA-ScR) (Tricco et al., 2018). A detailed, multistep search of PubMed, CINAHL, ProQuest and SPORTDiscus was conducted between May 2020 and July 2020, before being updated in April 2021. In addition to the electronic database search, reference lists from included articles were reviewed for additional articles. To ensure a broad search, key words were truncated to allow for variations in spelling and combined using Boolean operators in addition to the use of MeSH terms to allow for review of all relevant articles. The full electronic search for the PubMed database is provided in Table 2. Data extraction and synthesis WM extracted data from publications meeting the inclusion criteria into an Excel spreadsheet. Data extraction, grouping and plotting were performed by WM in line with previously published recommendations (Peters et al., 2020), where extracted data included author, year of publication, participant characteristics, methods for diagnosing Achilles tendinopathy and outcome measures. Data was extracted in tabular and graphical forms with results grouped by study design and categorised according to the hierarchy of evidence (Daly et al., 2006;Evans, 2003;Merlin, Weston & Tooher, 2009). Diagnostic criteria were presented in tabular form including year of publication, population, subjective and objective measures. Terminology and outcome measures were presented in graphical form with terminology grouped by publication year and outcome measures grouped by purpose of measure (disability, pain, psychological, quality of life). Following data extraction, data synthesis was performed according to a previously published methodological framework (Thomas & Harden, 2008). Data was synthesised  (Vicenzino et al., 2020) to identify areas of overlap and gaps in the current evidence. Studies could be allocated to multiple groups. Quality appraisal was not required as per recommended methodology for scoping reviews (Peters et al., 2020;Arksey & O'Malley, 2005).

Selection of sources of evidence
The search results are displayed in the PRISMA Flow Diagram (Fig. 2). The search strategy generated 11,561 results with two further results identified via reference list searching. Following duplicate removal and title and abstract screening, 554 full-text articles were Verrall Von Wehren et al., 2019;Wang et al., 2012;Wei et al., 2017;Xu et al., 2019;Zellers et al., 2019;Zhang et al., 2017;Zhang et al., 2020;Zhuang et al., 2019;Romero-Morales et al., 2019b) were included in this scoping review.

Characteristics of sources of evidence
In grouping the included articles by publication type, narrative reviews were the most common (27.2%) followed by cohort studies (19.6%), case control studies (18.8%), randomised controlled trials (12.7%), cross-sectional studies (10.8%), case reports (3.8%), protocols (3.2%), systematic reviews (1.9%), clinical guidelines (1.9%) and one consensus statement (0.6%). The years of publication of included studies ranged from 1980 to 2021, with 2017 to 2020 producing the most publications. Table 3 provides the general characteristics of the reviewed studies, including year of publication, type of publication, terminology and tendinopathy location. As highlighted in Fig. 3, the terminology used to describe tendon pain varied, with 'tendinopathy' being the most prevalent term used to describe tendon pain. Thus, during this scoping review, tendinopathy, will be used to describe pain located in the Achilles tendon that impairs function.

Clinical guidelines and consensus statements
Two of the included clinical guidelines Martin et al., 2018) discussed midportion Achilles tendinopathy, with one clinical guideline  and one consensus statement  discussing insertional Achilles tendinopathy (Table 4). Clinical measures used to diagnose Achilles tendinopathy was consistent across the clinical guidelines and consensus statement, with location of pain being the main differentiating factor between diagnosing midportion or insertional tendinopathy. Common methods with which midportion tendinopathy was diagnosed included subjective reporting of pain located in the Achilles tendon 2-6 cm above the calcaneal insertion that is increased with tendon loading and reported tendon stiffness. Similarly, insertional tendinopathy was diagnosed via subjective reporting of pain and swelling at the calcaneal insertion of the Achilles tendon. Pain on palpation was utilised to confirm clinical diagnosis in both midportion and insertional tendinopathy. While additional objective tests for midportion tendinopathy included the 'Painful Arc Sign' and 'Royal London Hospital Test'.

Systematic reviews
All three included systematic reviews assessed midportion Achilles tendinopathy (Table 5) Magnussen, Dunn & Thomson, 2009). Subjective reporting of pain with tendon loading was included as a diagnostic feature of midportion Achilles tendinopathy in all three systematic reviews Magnussen, Dunn & Thomson, 2009). Two of the systematic reviews  identified the location of tendon pain Table 3 Characteristics of included studies.

Characteristics
No. of studies (n)
as 2-6 cm above the calcaneal insertion, with one (Magnussen, Dunn & Thomson, 2009) defining the location of tendon pain as 2-7 cm above the calcaneal insertion. Palpation of the Achilles tendon, passive dorsiflexion, pain with single-leg heel raise and pain hopping or jumping were included as clinical tests in all included systematic reviews Magnussen, Dunn & Thomson, 2009). Two of the systematic reviews  included the 'Painful Arc Sign' and 'Royal London Hospital Test' as diagnostic measures for midportion Achilles tendinopathy. Table 6 highlights the characteristics of the included randomised controlled trials.

Protocols
Of the five included protocol studies, two studies  investigated midportion Achilles tendinopathy, one study  investigated insertional Achilles tendinopathy and two studies Post et al., 2020) investigated both insertional and midportion Achilles tendinopathy (Table 12). The most common reported subjective criteria utlised to diagnose Achilles tendinopathy was location of pain, with midportion Achilles tendinopathy defined as pain 2-6 cm above the calcaneal insertion in two studies , and 2-7 cm above the calcaneal insertion in one study . Insertional tendinopathy was defined as the distal 2 cm of the Achilles tendon in one study  and the Achilles 'insertion' in another study . Clinical diagnostic tests varied with three studies Mansur et al., 2017) including palpation, two studies Post et al., 2020) including pain during a single-leg heel raise and two studies including pain during hopping (Aggarwal et al., 2015;O'Neill et al., 2019). One study did not specify objective clinical tests .

DISCUSSION Overview
The clinical diagnosis of tendinopathy is commonly determined via both patient history and clinical tests (Cook et al., 2016;Coombes, Bisset & Vicenzino, 2015;Lewis, 2016;Lewis et al., 2015;Maffulli, Khan & Puddu, 1998;Malliaras et al., 2015;Scott et al., 2013). However, with no consensus on gold standard clinical tests with which to diagnose tendinopathy (Docking, Ooi & Connell, 2015), many research studies utilise a variety of measures to diagnose Achilles tendinopathy . The primary aim of this scoping review was to provide a method for clinically diagnosing Achilles tendinopathy that aligns with the nine core health domains. In order to achieve this, specific objectives were determined that included identifying the most common clinical tests used to diagnose Achilles tendinopathy, identifying the most common outcome measures used to assess Achilles tendinopathy, and summarising the studies to date. This will allow for greater consistency in both research and clinical settings. Additionally, this review aimed to identify the both the areas of strength and weakness

Terminology
As highlighted in Fig. 3, 'Tendinopathy' was the most commonly term used to describe persistent Achilles tendon pain, particularly in more recent studies. This scoping review aligns with the previous consensus statements advocating the consistent use of the term tendinopathy to describe persistent Achilles tendon pain and associated loss of function in relation to mechanical loading . There was a noticeable reduction of the use of alternative terms such as tendinitis and tendinosis, particularly since 2018, indicating progression towards unifying the terminology used to describe the clinical condition of persistent pain and dysfunction in the Achilles tendon that is associated with mechanical loading.
A difficulty identified in this scoping review was the inclusion of symptom duration as a measure to diagnose Achilles tendinopathy (Tables 6, 7, 8 and 9). When used as a measure, duration of symptoms varied significantly from four weeks up to 12 months, making identifying a consistent duration of symptoms to diagnose Achilles tendinopathy difficult and potentially contributing to the different terminology used within research and clinical practice. The term tendinitis indicates an inflammatory condition of the Achilles tendon that may develop symptoms in a shorter duration of time, whereas tendinosis indicates a change in tendon structure that would require a longer duration of time for symptoms to develop . Additionally, the clinical condition of Achilles tendinopathy does not display the characteristics of an inflammatory response such as with tissue tearing (Cook et al., 2016), and the structural changes, as those expected in tendinosis, are not required to be present for pain or dysfunction to develop (Cook et al., 2016).
The nine core health domains of tendinopathy Vicenzino et al. (2020) reported that the lack of agreed upon tendon health related domains impedes the progress of tendinopathy research. The nine identified domains (patient rating of overall condition, pain on activity or loading, participation, function, psychological factors, disability, physical function capacity, quality of life, and pain over a specified timeframe) should allow for greater consistency in the reporting of tendon research (Vicenzino et al., 2020). This scoping review further highlights the inconsistency in the methods used to diagnose and assess Achilles tendinopathy. There was variation in the methodology used to clinically diagnose and assess Achilles tendinopathy for all key themes; subjective history, clinical tests and outcome measures.

Subjective history
Multiple measures were identified to determine a diagnosis of Achilles tendinopathy from the subjective interview (Tables 4,5,6,7,8,9,10,11 and 12). The most commonly used measure was self-reported location of pain, with midportion Achilles tendinopathy most commonly being defined as an area located 2-6 cm above the calcaneal insertion of the Achilles tendon. Insertional tendinopathy was most commonly defined as the distal 2 cm of the Achilles tendon. Additional measures included pain with tendon loading activity, duration of symptoms, and tendon stiffness following tendon loading or at a particular time of the day (i.e. morning stiffness). Interestingly, while a change in Achilles tendon loading activity (both an increase and decrease) is considered a catalyst for Achilles tendinopathy (Cook et al., 2016), it was only utilised as a specific criterion in nine of the included studies Barker-Davies et al., 2017;Cook, Khan & Purdam, 2002;Feilmeier, 2017;Nichols, 1989;Sorosky et al., 2004).

Objective clinical tests
As with subjective history, numerous clinical tests were identified to diagnose Achilles tendinopathy (Tables 4,5,6,7,8,9,10,11 and 12). The most commonly identified clinical test for Achilles tendinopathy was tendon palpation (including pain on palpation, localised tendon thickening or localised swelling). Although, palpation is commonly used to identify the region of pain and is a common clinical measure used to diagnose Achilles tendinopathy Reiman et al., 2014;Martin et al., 2018), studies reported multiple regions of interest for midportion Achilles tendinopathy. Painful regions were described as the 'midportion', 'middle third', 2 to 4, 2 to 5, 2 to 6, 2 to 7, 4 to 6 and 4 to 7 cm above the calcaneal insertion. Similarly, the region of interest in insertional Achilles tendinopathy was described as the 'insertion', calcaneal tuberosity, distal 2 cm, and distal 5 cm.
While there was consistency in the included studies in their use of palpation as a clinical test, there is significant variation in the additional clinical tests used to confirm a diagnosis of Achilles tendinopathy (Tables 4,5,6,7,8,9,10,11 and 12). Further clinical tests used to assess Achilles tendinopathy included tendon pain during loading activities (single-leg heel raises and hopping). The most frequently used clinical, tendinopathy specific tests, were the Royal London Hospital Test and the Painful Arc Sign. The Royal London Hospital Test is considered positive when the is a reduction in palpable Achilles tendon pain on ankle dorsiflexion . The Painful Arc Sign is considered positive when the area of swelling identified with palpation moves with active ankle plantarflexion and dorsiflexion .

Outcome measures
As was the case for the clinical features, there were significant variations in the outcome measures utilised for making a diagnosis of Achilles tendinopathy (Fig. 4). While overall disability and participant perceived pain were commonly measured, the impact of Achilles tendinopathy on quality of life and psychological factors were rarely measured. Psychological factors such as pain efficacy, catastrophisation and kinesiophobia scales were identified as important outcome measures in the diagnosis tendinopathy (Vicenzino et al., 2020), which aligns with the identified psychological outcome measures (PES, TKS and PCS). Similarly, disability measures that combine patient rated pain and function in relation to tendon-specific activities were identified as integral to monitoring tendinopathy outcomes. This scoping review identified the VISA-A questionnaire as the most commonly used outcome measure to monitor Achilles tendinopathy. In addition to psychological factors and disability, overall quality of life was identified as a core health domain in tendinopathy (Vicenzino et al., 2020). The scoping review identified three different outcome measures (SF-12, SF-36 and EQ-5D-5L) that were utilised to assess participant quality of life.
An example evidence-based method for clinically diagnosing Achilles tendinopathy While there was significant variation in the methods used to diagnose Achilles tendinopathy, some common themes can be identified. When considering a consistent method for diagnosing and assessing Achilles tendinopathy, it is important to ensure research follows consensus recommendations on both terminology used and reporting outcomes Vicenzino et al., 2020). Thus, Table 13 provides an Self-reported location of pain Clinician asks patient "Can you point out where you get your pain" Pain located 2-6 cm above the calcaneal insertion (midportion) Pain located in the distal 2 cm of the Achilles tendon N/A Self-reported pain with tendon loading Patient reported intensity of pain using a VAS or NPRS while performing an Achilles tendon-specific loading task (single-leg heel raise, hopping) Patient reported increased pain on a VAS or NPRS with Achilles tendon-specific loading task (single-leg heel raise and hopping) Pain with loading or activity Self-reported tendon stiffness or pain over a specified time Clinician asks about pain and stiffness over specified timeframes (e.g. morning, night, 24 hours) Patient reported morning stiffness or pain Patient reported pain or stiffness at the onset of activity that may "warm-up" Pain over a specified time Self-reported overall rating of Achilles tendon Clinician asks "Can you rate your Achilles tendon where 100% represents no problems and 0% is the worst-case scenario" Patient reported level of condition Patient rating of overall condition

Objective tests
Palpation Performed by the clinician gently palpating the whole length of the tendon in a proximal to distal direction Patient reported pain located 2-6 cm above the calcaneal insertion (midportion) with or without subjective opinion of tendon thickening or swelling Patient reported pain located in the distal 2 cm of the Achilles tendon with or without subjective opinion of tendon thickening or swelling Performed by the clinician palpating the tendon for any local tenderness with the ankle either in neutral position or in slight plantarflexion. The ankle is then actively dorsiflexed and plantarflexed. With the ankle in maximum dorsiflexion, the portion of the tendon found to be tender is palpated again.
Patient reported pain on palpation reduces significantly or disappears with maximum dorsiflexion N/A Painful Arc Sign Performed by the clinician identifying the intratendinous swelling in the tendon and asking the patient to actively dorsiflex and plantarflex the ankle joint observing the movement of the swelling between the malleoli The intratendinous swelling moves relative to the malleoli with the Achilles tendon during the ankle movement N/A

VISA-A
The VISA-A questionnaire is a valid and reliable tool to evaluate clinical severity of Achilles tendinopathy that has been translated into multiple languages. Patients can self-administer the questionnaire The maximum score is 100, with healthy subjects scoring a minimum of 96 .

PCS
Patients are asked to indicate the degree to which they have the above thoughts and feelings when they are experiencing pain using the 0 (not at all) to 4 (all the time) scale.
A total score is yielded (ranging from 0-52), with a score of 30 or below indicating a clinically relevant level of catastrophising (Scott et al., 2013).

SF-12
The SF-12 is a self-reported outcome measure assessing the impact of health on an individual's everyday life.
The SF-12 creates two summary scores, mental health and physical health (Pham et al., 2014).

Quality of Life
Note: N/A, not applicable; cm, centimetres; VAS, Visual Analogue Scale; NPRS, Numerical Pain Rating Scale; VISA-A, Victorian Institute of Sport Assessment-Achilles; PCS, Pain Catastrophising Scale; SF-12, 12-Item Short Form Survey.
amalgamation of the common features used to diagnose Achilles tendinopathy identified in the scoping review and the previously identified nine core health domains for tendinopathy (Vicenzino et al., 2020). While the VISA-A is Achilles tendon specific, any validated and reliable pain questionnaire and quality of life questionnaire may be used in place of the Pain Catastrophising Scale and SF-12.

Limitations
This review was limited to publications in English, which may have excluded key studies published in other languages. Additionally, the screening, inclusion, exclusion and data extraction was performed by one reviewer (WM), which decreases the probability all relevant studies were identified for review and could lead to reviewer bias. The methodological quality of the studies was not assessed as per guidelines for completing scoping reviews (Peters et al., 2020;Arksey & O'Malley, 2005), meaning studies of poor design are given equal weighting to those of better quality, however, the descriptive nature of the scoping review limits the potential impact of individual studies' methodological quality on results. The aim of a scoping review is to provide an overview of all literature within a field of evidence (Pham et al., 2014), and while there is no specific requirement for methodological quality appraisal, assessing individual literature methodological quality utilising a standardised tool may help authors identify gaps in the literature related to low quality research in addition to lack of research.

CONCLUSIONS
The specific objectives, including the most common clinical tests used to diagnose Achilles tendinopathy and identifying the most common outcome measures used to assess Achilles tendinopathy were highlighted, with the scoping review identifying the significant variation in the methodology and outcome measures used to diagnose Achilles tendinopathy. This scoping review provides a detailed summary of the current evidence and common themes were identified in the available research to provide an evidence-based method to diagnose Achilles tendinopathy utilising both subjective and objective testing, in addition to recommendations regarding common outcome measures. The primary aim of this scoping review was to identify and provide a method for clinically diagnosing Achilles tendinopathy that aligns with the nine core health domains and a method for diagnosing Achilles tendinopathy is proposed, that includes both results from the scoping review and recent recommendations for reporting results in tendinopathy. The development of a method for the clinical diagnosis of Achilles tendinopathy is key to developing greater homogeneity in future research. By standardising the clinical diagnosis of Achilles tendinopathy, future research is able to investigate other areas of this complex condition and identifying possible subclassifications of Achilles tendinopathy and thus improving tailored individual treatment programmes or monitoring patient progress. Additionally, an evidence-based method for the clinical diagnosis of Achilles tendinopathy will allow clinicians to be more confident with their diagnosis and provide patients with greater certainty.