Author(s): Laurenie Louissaint, MD, MS, Richard G. Chang, MD, MPH
Originally published: July 20, 2012 Last updated: November 8, 2021
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Disease/Disorder

Definition

Achilles tendinopathy (AT) is an umbrella term used to describe a spectrum of tendon disorders including tendinosis and paratendinopathy, which all present with similar clinical symptoms of pain, swelling and impaired Achilles tendon function. Tendinopathy can be acute or chronic (lasting longer than 12 weeks). The two anatomical classifications include insertional (at the calcaneus-Achilles tendon junction) and non-insertional (2 – 6 cm proximal to the insertion of the Achilles tendon onto the calcaneus).4,5

Etiology

AT is frequently associated with overuse injury despite the tendon being able to bear loads in excess of 3500N.3 In addition to sporting activities, there are other intrinsic and extrinsic factors contributing to development of this condition. Intrinsic factors include increasing age, gender, systemic diseases (diabetes, rheumatologic conditions, and metabolic disorders), biomechanical abnormalities (foot pronation, leg length discrepancy, pes cavus, and/or varus foot deformity) and obesity. Extrinsic factors include drugs (fluoroquinolones), excessive mechanical overload, and training errors such as excessive hill training and poor shock absorption.4,5

Epidemiology including risk factors and primary prevention

Achilles tendon pathology is associated with 50% of all sports related injuries. 75% of Achilles tendon ruptures occur in middle aged men participating in sports.3 AT may affect 9% of recreational runners and cause 5% of professional athletes to end their careers.5 Up to 4% of active adults may have asymptomatic degeneration, and it is frequently linked with jumping and running activities. Other causes of AT include fluoroquinolone use (0.2-2.0%) and systemic diseases (2.0 %) such as ankylosing spondylitis, psoriatic and rheumatoid arthritis. One study described the prevalence of non-insertional AT as 2.01 per 1000 patients.3

Patho-anatomy/physiology

The Achilles tendon originates from the gastrocsoleus complex and inserts onto the calcaneus distally. Histologically, it is composed of tenoblasts and tenocytes (90-95%), chondrocytes (5-10%) and some synovial cells. The extracellular matrix is made up of glycosaminoglycans, proteoglycans, and glycoproteins. Collagen accounts for 70-80% of the dry weight of the tendon and is composed primarily of type I (95%), type III, V, and XII. Elastin accounts for 2% of the dry weight; however, the tendon can undergo 200% strain before failing. Collagen forms fibrils, fibers, fascicles which come together to form bundles surrounded by an endotenon which carries the blood supply, nerves and lymphatics.3

Biomechanical intrinsic factors which contribute to AT include hyperpronation of the foot, along with ankle equinus (frequently caused by pes planus). Ankle equinus is defined by ankle dorsiflexion limited to 10-20°. This causes increased foot pronation in order to gain the added benefit of increased dorsiflexion in order to maintain proper gait mechanics. This excessive hyperpronation at the subtalar joint causes the gastrocnemius-soleus complex and tibiialis posterior to eccentrically contract with greater force. This compensation occurs to decelerate the rotation of the lower extremity and pronation of the foot. The frequent forceful contraction contributes to the development of AT.14

In AT, the tendon becomes thickened, brown and uneven. At the cellular level, there is an increase in the number of tenocytes, concentration of glycosaminoglycans, disorganization of the collagen fibers and neovascularization.  In chronic AT, there is an increased concentration of type III collagen, fibronectin, tenascin C, aggrecan, and biglycan.4

Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)

The majority of patients with AT recover fully and are able to return to sports participation. Grading is based on the severity of symptoms.

Grade 1: Morning discomfort in tendon, which resolves shortly after waking.
Grade 2: Pain during athletic activities that does not interfere with performance.
Grade 3: Pain that interferes with performance.
Grade 4: Pain that precludes sports participation.

In AT, tendon injury/repair occurs in three stages:4

Stage 1: Inflammatory – Lasts a few days with release of vasoactive and chemotactic factors
Stage 2: Proliferative – Lasts a few weeks and type III collagen levels peak
Stage 3: Modeling – Decreased collagen production and fibrous consolidation process beginning after 6 weeks.

Specific secondary or associated conditions and complications

Achilles tendon rupture is the most feared complication of AT. It may happen acutely or as an extension of a pre-existing partial tear of the tendon’s dorsal surface. Fluoroquinolone use has been linked to an increased risk of rupture, particularly in older populations taking concomitant oral steroids.4,6 Histologic examination confirms the presence of degenerative changes in > 75% of cases.1

Inflammation of the subcutaneous or retrocalcaneal bursae may mimic insertional AT. Extrinsic factors, such as high-heel or tight-fitting shoes with hard heel counters have been implicated in the development of calcaneal bursitis. In a small percentage of patients, the etiology may be infectious or reactive.  In skeletally immature athletes, calcaneal apophysitis (Sever’s disease) is the most common cause of Achilles-related pain.  Symptoms of Sever’s disease respond well to activity modification.

Essentials of Assessment

History

Patients with AT generally complain of a dull, burning pain along the tendon itself. The triad of pain, swelling and functional impairment are indicative of AT. It is important to evaluate for the intrinsic and extrinsic risk factors as outlined above.

A sudden “popping” sensation followed by pain and swelling during sudden pivoting movements or rapid acceleration should be suspicious for a tendon rupture.

Physical examination

Examination of the Achilles tendon begins with inspection of the tendon for any bruising or swelling. The tendon should be palpated along its length to assess for tenderness, thickness or any palpable gaps along the tendon. The ankle should be ranged in dorsiflexion and plantarflexion, which may reveal some crepitus. It is important to remember that an Achilles tendon rupture may be missed on exam due to inability to palpate a defect in the tendon, patient’s inability to walk and plantarflex the tendon, or a painless tendon rupture.

The sensitivity of palpation to detect a tendon abnormality is about 0.73. Other tests that can be used to assess tendon pathology include Matles test, O’Brien’s test, Copeland test, and the Thompson test. The Thompson and Matles tests have the highest sensitivities, close to 0.9.7

Functional assessment

As part of a thorough patient evaluation, it is important to assess for any gait and biomechanical abnormalities, which may be present such as leg length discrepancy, pes planus, or varus deformity of the foot.

Laboratory studies

If a systemic inflammatory process is suspected, a laboratory work-up may include complete blood count with differential, erythrocyte sedimentation rate, C-reactive protein, rheumatoid factor, and anti-DNA antibody levels.

Imaging

Plain radiography has a low yield in detecting soft tissue pathology However, it can be helpful for detecting bony pathology such as enthesopathy.  Both ultrasound (US) and magnetic resonance imaging (MRI) provide the necessary anatomical detail for detecting AT pathology. Typical findings include a thickened paratenon, heterogeneity of tendon structure and increased vascularity of the ventral aspect of the tendon on color Doppler-augmented US and contrast-enhanced MRI.  Early AT may present with increased fluid surrounding the tendon. Increased vascularity of the tendon’s dorsal side may indicate a partial tear, which may progress, unless managed appropriately.3

Hartgerink et al performed a study of 26 Achilles tendon tears using ultrasound and compared this to surgical findings. They found a sensitivity of 100%, specificity of 83% and positive predictive value of 83% in detecting partial from full thickness tears using ultrasound15. This and other studies show that US is helpful in detecting AT, however MRI is necessary to establish a definitive diagnosis.16

Although ultrasound can provide insight on the anatomical and morphologic features of AT, it lacks the full capability to assess the tendon’s mechanical properties that are altered due to extrinsic factors that lead to the tendinopathy.

New advances in ultrasound-based technologies such as shear wave sonoelastography (SWE) and strain sonoelastography (SE) not only allow for the evaluation of both AT stiffness and elasticity, but ultimately can aid in an early diagnosis.33 Schneebeli et al 2021 study compared SE to SWE and found that SE used with a reference material was able to detect elasticity changes between the different contraction levels compared to the latter. Further studies are needed to evaluate the mechanical properties in pathological tendons.34

Supplemental assessment tools

Visual analog pain scale (VAS) and Victorian Institute of Sports Assessment – Achilles (VISA-A), an 8-question survey, have been validated for use in the AT population17

Environmental

Training in inclement weather, excessive uphill or downhill running and physical deconditioning is associated with an increased risk of AT. Those at greater risk for Achilles tendon rupture tend to be older and less physically conditioned

Social role and social support system

Since rehabilitation of AT may require significant changes to training/competition regimen, assistance of a sports psychologist may be necessary.

Professional Issues

Each clinician should address any risk factors for rupture of the Achilles if the older patient returns to “weekend athletics” or if the high level athlete returns to the court or field. Treatment may vary for patients depending on their previous level of activity. For example, a high level athlete or individuals with physically demanding jobs will require more aggressive management. A full recovery is important to maintain their previous function. It is important for the clinician to determine the patient’s personal and professional needs in order to create a personalized treatment regimen. Physicians should also make patients aware that their rehabilitation management to full recovery may take time and weigh the patient’s personal desire to return to usual activity. As a general principle, their overall rehabilitation management should be closely monitored.

Rehabilitation Management and Treatments

Available or current treatment guidelines

According to the Orthopedic section of the American Physical Therapy Association 2018 practice guideline for midportion Achilles tendinopathy, the initial steps in conservative management of AT consisted of activity modification and an emphasis on mechanical loading in therapy (eccentric exercise), which was found to decrease pain and improve function.  Meanwhile, bracing, orthoses, splinting and elastic taping all were found to provide minimal or no benefit. Rigid taping may be used to decrease strain on the Achilles tendon and/or alter foot posture in patients with midportion Achilles tendinopathy. 35 In recalcitrant cases, surgery may be considered in those who fail conservative management.36 

At different disease stages

New onset/acute

  • Activity modification
  • Cryotherapy to control pain and edema.
  • Non-steroidal anti-inflammatory drugs (NSAIDs) reduce pain and inflammation and facilitate physical therapy. Studies between oral NSAIDs and placebo show no overwhelming evidence of quicker return to activity, but they are reasonable medications for pain relief.
  • Intratendinous steroid injections are not recommended due to reported increased risk of Achilles tendon rupture, although no randomized study has shown that to be true. However, adverse events have been reported in 82% of corticosteroid trials while only providing short term pain improvement.4,5
  • Once healing has begun patients can begin a rehabilitation program. Many systematic reviews show benefit of eccentric strength training (EST) in non-insertional AT.4

Subacute

  • Includes secondary prevention and disease management strategies
  • Gastrocnemius/soleus stretching and EST are important in maintaining mobility and decreasing muscle tension.
  • Therapeutic ultrasound decreases pain and swelling in the acute inflammatory phase of tendon injuries, but there is lack of evidence to support its use in AT.4,5

Chronic/stable

  • Includes secondary prevention and disease management strategies and rehabilitation strategies that intend to optimize function.
  • Studies have shown eccentric strengthening can produce normalization of tendon tissue in non-insertional Achilles tendinopathy2,20-22
  • With respect to injections, ultrasound guided paratenon injection (aka high-volume image guided injection,) using high volumes of local anesthetic, saline, with or without corticosteroid is an option and has a role for chronic cases of non-insertional AT. Current studies have shown that the procedure is safe and there are benefits in improving pain and function (yet short term), but more study is needed.18-20
  • As stated above, intratendinous corticosteroid injections are not recommended because of the high risk of adverse events including Achilles tendon rupture.5,8,20
  • In chronic cases, a multidisciplinary team is helpful to optimize patient outcomes.  Ideally, the physiatrist would lead a clinical team of physical therapists, orthotists, surgical consultants, nutritionist, and a sports psychologist.
  • For recalcitrant pain not improved with lifestyle modification, medications, and physical therapy, surgical management can be considered. Repair of an elongated or a partially torn tendon should be considered for patients with high functional demands. Physiatrist’s role should be to help establish the necessity of surgery in certain clinical scenarios and to ensure conservative options have been exhausted and biomechanical and other risk factors addressed.
  • Several techniques can be used during both open and percutaneous procedures, including removal of the damaged peri-tendinous tissue, longitudinal incisions on the tendon to stimulate repair, or longitudinal incisions with damaged intra-tendinous excision.37 The incidence of postsurgical complications is 11%.4,5

Patient & family education

Patients should be counseled and educated regarding theories supporting the use of physical therapy and the role of mechanical loading; modifiable risk factors, including BMI and shoe wear; and typical time course for recovery from symptoms.35

Emerging/unique interventions

Given the current emphasis on healthcare metrics, patient reported outcome measures (PROM) help measure a patient’s perceived impact from Achilles tendinopathy. Both VAS and The Victorian Institute of Sports Assessment–Achilles tendinopathy questionnaire (VISA-A) can be used to assess patient’s pain and stiffness. Either the Foot and Ankle Ability Measure (FAAM) or the Lower Extremity Functional Scale (LEFS) can also be used to assess activity and participation in clinical settings. 35

Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills

Patient education should focus on preventive strategies, and validated outcomes measures (e.g., PROM) should be employed to document treatment progress. Training and exercise modification is very important.  Analysis of gait and incorporation of strengthening other muscles besides the ankle/foot complex, such as the core and hip would be ideal in decreasing the risk for further injury.

Cutting Edge/Emerging and Unique Concepts and Practice

Cutting edge concepts and practice

Extracorporeal shock wave therapy (ESWT)is believed to initiate a reparative process that promotes tenocyte, proliferation, collagen synthesis, neovascularization and pain relief.28

Although safe and well tolerated, the high diversity of application methodologies prevents ESWT effectiveness for Achilles tendinopathy from being fully recommended. Further multicenter, comparative randomized controlled studies are still needed.29    

Topical glyceryl trinitrate theoretically increases nitric oxide concentrations leading to improved fibroblast function and wound healing.  One randomized, double blind, placebo controlled study showed improvement in symptoms, while others found no difference.4,6

A number of different injectable therapies are available, but high-quality research comparing the effectiveness of these interventions is lacking.

In 2015, Lynen et al compared three once weekly ESWT and two once weekly ultrasound guided hyaluronic acid paratendinous injections for AT.  Statistically significant improvements in pain were reported with the hyaluronic acid injection group at one, three, and sixmonths.8  

Platelet-rich plasma (PRP) injections appear to show promise in recalcitrant mid-portion AT.9,10 PRP is believed to facilitate healing due to its high concentration of growth factors, which may promote tendon remodeling, especially when combined with percutaneous needle tenotomy. Krogh et al, in a randomized placebo controlled blinded study of 24 patients with non-insertional Achilles tendinopathy compared one single ultrasound guided PRP injection versus a saline injection over a 3 month period found no statistically significant improvement in VISA-A score.11   Limitations of this study included a poor follow up rate, questionable needle tenotomy technique, and an unstructured post-procedure rehabilitation protocol.   Based on the available research, PRP therapy may be reserved for those patients who fail to improve with anti-inflammatory medications, activity modification, bracing, and physical therapy.10,11 Kearney et al most recent RCT in 2021 did not support the use of PRP for the treatment of chronic midportion AT.30 Due to conflicting literature, a greater call for larger studies (and in comparison to surgical techniques) is required for further clarification.5,9,18-21

Prolotherapy induces an inflammatory process, which initiate the body’s wound-healing cascade, and lead to cellular proliferation, collagen deposition, and eventually tissue repair,14–16 thereby leading to pain reduction and functional improvement.  Dextrose, one of the most commonly used substances, is hypothesized to initiate a wound healing cascade of inflammation, granulation tissue formation, matrix formation, and remodeling.31 There is insufficient evidence to support the clinical benefits of dextrose prolotherapy. More high-quality randomized controlled trials are warranted to establish the benefits of prolotherapy. Other sclerosing agents, including polidocanol, which promote vessel thrombosis, may result in decreased tissue inflammation and neovascularity in patients with chronic AT.4,6 Ebbesen et al 2018 RCT established polidocanol as a safe treatment, but the study only provided mid-term effects similar to the placebo group, and questioned its use in chronic AT.32    

Percutaneous needle tenotomy of the tendon is a minimally invasive option for patients’ refractory to conservative treatment. Of note, this treatment option is based on existing literature for treatment for other chronic tendinosis such as lateral epicondylosis.25,26 A separate retrospective study of 26 patients by Ellis et al., 88.5% reported pain relief in up to an 18 month follow up period).21,22,27

Using the similar principles found with needle tenotomy, percutaneous ultrasound tenotomy, uses ultrasound energy toemulsify, debride, and remove pathologic tendon tissue. Tenex is one example device that uses such technology. There appears to be positive results with animal studies, with possible benefit in humans.38,39

An emerging novel treatment is tendon scraping, which involves using a scalpel or needle to separate neovascularization between the affected tendon and the adjacent fat pad.40,41,43 Existing studies by Alfredson et al, which have used either a scalpel or percutaneous scraping with a needle under ultrasound and color doppler guidance for patients with midportion Achilles tendinopathy,  appear to show similar decreases in pain, function, complication rate, and a quicker return to sport and tendon loading when compared to prolotherapy and polidocanol injections.41,42,43

Another percutaneous technique that has been studied is radiofrequency microtenotomy and coblation of the affected tendon. Here, a radiofrequency probe generating at a low temperature (40-70 degrees Celsius) is activated for 0.5 seconds while light axial pressure is applied to puncture the tendon perpendicularly over a number of areas.21,22 Approximately 20 points over the tendon are mapped prior to the procedure. 21  Based on a 2012 review of 47 patients by Shibuya et al., their study reported that 14.7% of patients had to be re-operated on due to ineffective results, with 6.4% of patients having AT rupture (associated with higher BMI).22,23 Other smaller studies have reported more successful results (“90-95 % success rate”) lasting at least 6 months to 3 years.24  Due to the lack of level 1 studies with other studies using concurrent potentially confounding surgical techniques (e.g. arthroscopy, adhesiolysis) and variable results, this treatment option should not recommended.

Gaps in the Evidence-Based Knowledge

Although, VAS is used as a subjective indicator of a patient’s symptoms and an indicator of a modality’s effectiveness, there is a lack of studies using objective testing to monitor the progression of AT or predict the risk of tendon rupture. Future double-blinded randomized controlled studies are needed to clarify the best option among the novel therapies and procedures available (e.g., PRP, prolotherapy, ESWT, and tendon scraping) for pain reduction, as well as functional improvement in non-surgical candidates and comparing the latter to surgical candidates.4,5,6,18-20,22

References

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  6. Maffulli N, Papalia R. Pharmacological interventions for the treatment of Achilles tendinopathy: a systematic review of randomized controlled trials. British Medical Bulletin. 2015; 113; 101-115.
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  8. Lynen N, De Vroey T, Spiegel I. Comparison of peritendinous hyaluronan injections versus extracorporeal shock wave therapy in the treatment of painful achilles’ tendinopathy: a randomized clinical efficacy and safety study. Archives of Physical Medicine and Rehabilitation. 2017; 98: 64-71.
  9. Di Matteo B, Filardo G, Kon E, Marcacci M. Platelet-rich plasma: evidence for the treatment of patellar and Achilles tendinopathy–a systematic review. Musculoskelet Surg. 2015;Apr 99(1):1-9.
  10. Guelfi M, et al. Long-term beneficial effects of platelet-rich plasma for non-insertional Achilles tendinopathy. Foot and Ankle Surgery. 2015;Sep 21(3):178-81.
  11. Krogh T, Ellingson T. Ultrasound-guided injection therapy of Achilles tendinopathy with platelet-rich plasma or saline. The American Journal of Sports Medicine. 2016; 44(8): 190-197.
  12. Calder J, Stephen J, Dijk N. Plantaris Excision Reduces Pin in Midportion Achilles Tendinopathy Even in the Absence of Plantaris Tendon. The Orthopaedic Journal of Sports Medicine. 2016; 4(12): 1-9
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  16. Kayser R, Mahlfeld K. Partial rupture of the proximal Achilles tendon: a differential diagnostic problem in ultrasound imaging. Br J Sports Med. 2005;39(11):838.
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  18. Caudell GM. Insertional Achilles Tendinopathy. Clin Podiatr Med Surg.2017;34:195–205,
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  42. Alfredson H, Ohberg L, Zeisig E, Lorentzon R. Treatment of midportion Achilles tendinosis: similar clinical results with US and CD-guided surgery outside the tendon and sclerosing polidocanol injections. Knee Surg Sports Traumatol Arthrosc. 2007;15(12):1504–9.
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Original Version of the Topic

Clark C. Smith, MD and Grigory Syrkin, MD. Achilles tendinopathy. 7/20/2012

Previous Revision(s) of the Topic

Richard G. Chang, MD, MPH, Brian Pekkerman, DO, Puneet Ralhan, DO. Achilles tendinopathy. 7/31/2017

Original Version of the Topic

Laurenie Louissaint, MD, MS
Nothing to Disclose

Richard G. Chang, MD, MPH
Nothing to Disclose