Tendons transmit force between muscles and bones and, when stretched, store elastic energy that contributes to movement.1 The tendinous portion of the gastrocnemius and soleus muscles merge to form the Achilles tendon, which is the largest and strongest in the body, but one of the most frequently injured.2,3 Conservative management options for chronic Achilles tendinopathy include eccentric (lengthening) exercises, extracorporeal shockwave therapy (ESWT), topical nitroglycerin, low level laser therapy, orthoses, splints or injections (e.g. corticosteroids, hyperosmolar dextrose, polidocanol, platelet-rich plasma), while a minority of patients require surgery (using open, percutaneous or endoscopic methods).4–8 Here we assess the management options for patients with chronic Achilles tendinopathy (lasting over 6 weeks).
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About Achilles tendinopathy
Achilles tendinopathy (see Box 1) is a common injury (with or without sporting activity).2,9 Insertional tendinopathy affects the insertion of the tendon on the calcaneum (comprising around 25% of cases); mid-portion (also called mid-substance or non-insertional) tendinopathy affects the tendon around 2–6cm above the insertion, where there is a region of hypovascularity (comprising around 75% of cases).10,11
Box 1: Tendinopathy
After injury, tendons typically undergo three healing phases: acute inflam-mation (lasting a few days); a ‘proliferative’ phase (lasting around 3 weeks) in which fibroblasts produce new collagen, and vascular endothelial growth factor facilitates neovascularisation; and a collagen remodelling phase with decreased cellularity and vascularity (lasting up to a year).12
Tendinopathy indicates a failed healing response, with haphazard proliferation of tenocytes, disruption of collagen fibres, increase in non-collagen matrix and neovascularisation.4
In adults aged 21–60 years, the incidence of mid-portion Achilles tendinopathy is around 2.35 per 1,000.9 The incidence is rising, mainly because more people participate in recreational and competitive sports.3 Risk factors for tendinopathy include strenuous physical activities such as running and jumping, ageing, diabetes mellitus, obesity, hypertension, dyslipidaemia, rheumatoid arthritis or other inflammatory joint diseases, the use of fluoroquinolone antibiotics, abnormal lower limb anatomy, sports training errors (e.g. high intensity or poor technique), poor equipment or unfavourable environmental conditions (e.g. heat, cold, humidity).2,8,11,13,14
The diagnosis of tendinopathy is based on pain (which in severe cases may interfere with activities of daily living), swelling and impaired performance; morning stiffness is common and patients may have decreased strength and endurance of the calf muscles.6,10,15 In the past, the term ‘Achilles tendonitis’ was used as the aetiology was assumed to be inflammatory (and treatment included corticosteroids and non-steroidal anti-inflammatory drugs).16,17 However, more recently, patho-anatomic studies have questioned this “due to the lack of inflammatory changes found in tendons”.16 Ultrasound studies may be helpful in making the diagnosis.
The initial management of Achilles tendinopathy is conservative (e.g. rest; correction of training errors, foot malalignments and muscle weakness; analgesia [e.g. paracetamol, NSAIDs]; an orthosis that puts the hindfoot in neutral). Early intervention is preferable as management becomes more complicated and less predictable once the condition becomes chronic.5 Other treatments that have been tried, particularly once the condition becomes chronic, include eccentric exercises, ESWT, topical nitroglycerin, low level laser therapy, orthoses, splints, injections or surgery.4–6,8
Few randomised controlled trials have been published comparing the effectiveness of different treatment methods for chronic tendinopathy.4
In concentric exercises, a muscle is shortened while contracting (e.g. a toe raise); in eccentric exercises, a muscle is lengthened while contracting (e.g. a controlled lowering of the body from the position of toe raise; see Figure and Box 2).4,6
Box 2: Eccentric exercises
The patient starts in a single-leg standing position with the weight on the forefoot and the ankle in full plantar flexion (involved leg only tip-toe on a step); the Achilles tendon is then eccentrically loaded by slowly lowering the heel to a dorsiflexed position (forefoot on step and heel below); the patient then returns to the starting position using the arms and other leg to avoid concentric loading (both feet tip-toe on step).18 Movements are slow and controlled with moderate but not disabling pain.8
In a systematic review,10 eccentric exercises were found to be superior to wait-and-see in two randomised controlled trials,19,20 superior to traditional concentric exercise in two randomised controlled trials21,22 but not a third,15 and superior to night splints in one randomised controlled trial.23 The potential unwanted effects include delayed-onset muscle soreness or exacerbation of the tendinopathy; these typically occur when the exercises are performed too quickly, incorrectly, or with too abrupt an increase in load.6
Extracorporeal shockwave therapy
In ESWT, a device (positioned using ultrasound or clinical symptoms) passes acoustic shockwaves through the skin to the affected area.24 The rationale for using ESWT is to stimulate soft-tissue healing and inhibit pain receptors.4,25
In a systematic review,10 ESWT was superior to wait-and-see and equivalent to eccentric exercises in one randomised controlled trial20 but not superior to placebo in another.26 Unwanted effects include transient reddening of the skin.20
In a randomised controlled trial, 50 people with chronic (at least 6 months) insertional Achilles tendinopathy received either ESWT or eccentric muscle training.27 At 4 months from baseline, the Victorian Institute of Sports Assessment – Achilles (VISA-A) score (the primary outcome measure, see Box 3) increased more with ESWT than eccentric exercises (ESWT: from around 53 at baseline to 79 vs. exercises: from 53 to 63; difference between groups p = 0.005; effect-size thresholds are 5 points for a small effect and 15 points for a moderate effect).28 More patients on ESWT reported success (“completely recovered” or “much improved” on a 6-point Likert scale; 64% vs. 28%, p < 0.02).
Box 3: Victorian Institute of Sports Assessment – Achilles (VISA-A) validated questionnaire
Duration of morning stiffness (0 = 100 minutes and 10 = 0 minutes)
Pain on stretching Achilles tendon (0 = strong severe pain; 10 = no pain)
Pain on walking (0 = strong severe pain; 10 = no pain)
Pain walking downstairs (0 = strong severe pain; 10 = no pain)
Pain during/immediately after 10 single leg heel raises from flat surface (0 = strong severe pain; 10 = no pain)
Number of single leg hops without pain (0 = none; 10 = 10)
Current sport/physical activity (0 = none; 4 = modified training and modified competition; 7 = full training and modified competition; 10 = competing at same or higher level than when symptoms began)
Duration of training and practice (maximum score 30 points for exercise over 30 minutes with no pain).
Scores summed; maximum 100 points if asymptomatic.29
Effect-size thresholds are 5 points for a small effect and 15 points for a moderate effect.28
In another randomised controlled trial, 68 people with chronic (at least 6 months) non-insertional Achilles tendinopathy received eccentric muscle training alone or with ESWT.25 At 4 months from baseline, the VISA-A score (the primary outcome measure) had increased more in the group receiving both treatments (from around 50 at baseline to 87 vs. from 51 to 73, p = 0.0016). More patients in the combination group reported success (“completely recovered” or “much improved” on a 6-point Likert scale; 82%% vs. 56%, p = 0.001).
Nitroglycerin is metabolised to release nitric oxide, which is thought to play a role in tendon healing through fibroblastic synthesis of collagen.1 Some trials have used a 5mg/24 hour glyceryl trinitrate patch (unlicensed use) cut into quarters and one quarter placed over the area of maximal tenderness/pain for 24 hours, then replaced with another quarter patch and so on.18
A systematic review found two randomised controlled trials of topical nitroglycerin in the treatment of chronic (over 6 weeks) Achilles tendinopathy; one trial found a benefit of nitroglycerin in terms of pain on activity or at night and tendon tenderness, but the other trial found no difference from placebo at 6 months on pain at rest or with activity.1 The most commonly described unwanted effect with this treatment is headache, which can be severe enough to stop treatment.18
Low level laser therapy
This treatment uses laser sources at powers too low to cause measurable temperature increases.30 At the cellular level, it may increase collagen production, down-regulate matrix metalloproteinases and decrease the capillary flow of neovascularisation.7
A systematic review found four randomised controlled trials or controlled clinical trials, involving a total of 175 patients, comparing laser with placebo.30 Two studies showed positive effects on pain scores at the final assessment and two were inconclusive, but the results of all four were not pooled together.30
Orthoses and splints
As increased pronation has been associated with Achilles tendinopathy, a foot orthosis has been tried for patients with this problem.8 A systematic review found only limited evidence from two small trials.8
Morning stiffness is common in athletes with Achilles tendinopathy, so a night splint might be effective in reducing this problem.31 In a randomised controlled trial, 58 patients with mid-portion tendinopathy (total of 70 tendons) received eccentric exercises with or without a night splint.31 The VISA-A score (the primary outcome measure) increased in both groups (no splints: from around 50 at baseline to 76 at 1 year, p < 0.01; with night splints: from 49 at baseline to 78 at 1 year, p < 0.01; no significant difference between groups).
In a systematic review,32 one randomised controlled trial was found that compared corticosteroid injections with placebo injections in a total of 48 patients with mid-substance Achilles or patellar tendinopathy for over 6 months. This study found no benefit of corticosteroids at 3 weeks in the subgroup of patients with Achilles tendinopathy (standardised mean difference [SMD] in pain score 0.73, 95% CI −0.11 to +1.56). The corticosteroid group had an increased risk of tendon atrophy (relative risk [RR] 20.92, 95% CI 1.32 to 331.74) and one Achilles tendon rupture was reported in the corticosteroid group (RR 1.53, 95% CI 0.06 to 36.23).
The rationale for using high-volume injections is to produce local mechanical effects causing neovessels to stretch, break or occlude, and to damage the accompanying nerve supply by trauma or ischaemia, decreasing pain.33 We found no randomised controlled trials evaluating high-volume injections for the management of the Achilles tendinopathy. One retrospective cohort of 30 patients suggested that image-guided injections of 10mL 0.5% bupivacaine hydrochloride with 25mg hydrocortisone acetate, followed by up to 40mL of normal saline was effective in returning patients to sport (19 of 21 patients returning questionnaires) but this approach requires further research before it can be recommended.33
Hyperosmolar dextrose (prolotherapy)
In prolotherapy, a solution of hypertonic glucose and local anaesthetic is injected alongside the painful area of the tendon, with the aim of stimulating inflammation (due to local tissue trauma caused by dehydration) followed by collagen deposition.7,34
In a systematic review, one randomised controlled trial was found comparing prolotherapy (weekly injections for 4–12 treatments), eccentric exercises, or both, in 43 patients with mid-portion Achilles tendinopathy for over 6 weeks.32 Compared with the exercise group, outcomes did not differ in the prolotherapy group (overall improvement at 12 weeks: RR 1.69, 95% CI 0.92 to 3.12; 26 weeks: RR 1.27, 95% CI 0.80 to 2.02; 52 weeks: RR 1.00, 95% CI 0.72 to 1.39) or in the combination group (data not shown). Because of the resources involved in carrying out the injections (e.g. radiologist trained in musculoskeletal pathology) and risks involved in skin puncture, it has been suggested that the treatment should be used only when conservative measures have been ineffective.35
Autologous blood injections
The rationale for using this is to introduce an assortment of growth factors to an area of tendinopathy.3 In a randomised controlled trial, 33 patients with Achilles tendinopathy in 40 tendons (mean duration 11 months) received eccentric exercises for 12 weeks with or without a peri-tendinous autologous blood injection.28 Improvements in VISA-A scores were similar at 6 weeks (7.7 units in injection group and 8.7 units in exercise-only group) but had improved more in the injection group by 12 weeks (improvement in VISA-A score 18.9 units vs. 9.4 units). The authors used effect-size thresholds of 5 (small effect) and 15 (moderate effect) and concluded that there is some evidence for small short-term symptomatic improvements with the addition of autologous blood injection, but that double-blinded studies with longer follow-up and larger sample sizes should be performed.
Platelet-rich plasma is a sample of autologous blood with concentrations of platelets above baseline values, obtained by centrifuging or filtering the autologous blood after anticoagulation.3 It is thought that inherent growth factors released from platelets encourage tenocyte migration and differentiation at the site of tendon injury, although the evidence for this remains weak.17
In a systematic review,32 one randomised controlled trial was found comparing platelet-rich plasma with placebo injections (each in addition to usual care with eccentric exercises) in 54 participants with chronic (over 2 months) mid-substance Achilles tendinopathy.36 Outcomes did not differ between the groups at 6 or 24 weeks (RR of improvement at 6 weeks: 1.00, 95% CI 0.44 to 2.28 and at 24 weeks 0.88, 95% CI 0.57 to 1.38; SMD in function score at 6 weeks 0.18, 95% CI −0.35 to +0.72 and at 24 weeks 0.05, 95% CI −0.48 to +0.59).36 The 1-year follow-up of the same trial also showed no difference between the groups.37
There is a proliferation of small blood vessels in tendinopathy, with nerve fibres alongside the neovascularisation, which may generate the pain associated with the condition.18 In theory, injecting a sclerosing agent such as polidocanol into the areas of neovascularisation could sclerose the vessels and eradicate pain-generating nerve fibres either directly (by destruction) or indirectly (by ischaemia).18,38
In a systematic review,10 polidocanol was superior to local anaesthetic in one double-blind randomised controlled trial involving 20 patients.38 However, in a more recent retrospective study of 48 patients with mid-portion Achilles tendinopathy (53 tendons) treated with polidocanol, no beneficial effect of the injections was shown; only 44% of patients were pain-free or had only minimal pain at 6 weeks.39
Only a minority of patients are recommended for surgery. Surgery aims to excise fibrotic adhesions; remove areas of failed healing; restore vascularity; and stimulate the remaining viable cells to initiate cell matrix response and healing.4 One of the least invasive procedures is percutaneous longitudinal tenotomy, which may be used for mild to moderate focal non-insertional Achilles tendinopathy.7 Another procedure, minimally invasive stripping, uses large diameter sutures that are passed through stab incisions and slid anterior to the tendon to free adhesions; this may be used in conjunction with longitudinal tenotomies.7 For moderate to severe tendinopathy, an open procedure can be performed, enabling removal of difficult adhesions.7 If over 50% of the cross-sectional area of the tendon is diseased, after debridement, the Achilles tendon may be augmented by a well-vascularised graft by transfer of the flexor hallucis longus tendon.7 These procedures are supported by ‘fair’ evidence (case control studies or case series).7 However, operative complications include skin necrosis, superficial and deep infections, seroma or haematoma formation, sural neuritis, new partial ruptures, deep venous thromboses, and sensitive or hypertrophic scars.7 Open surgery requires a relatively long postoperative rehabilitation, and normally takes 6 months before patients are back to full tendon-loading activity.40 Minimally invasive surgery may lead to reduced peri-operative morbidity, shorter hospital stay and reduced costs, but randomised controlled trials comparing these techniques with open surgery are required.41
In a randomised controlled trial, 20 patients with chronic (mean 28 months, range 6–150 months) painful mid-portion Achilles tendinosis were treated with either polidocanol or open surgery.40 At 12 weeks, six out of nine patients in the polidocanol group (one patient excluded, reason not stated) were satisfied and back to their previous recreational or sport activity (their mean VAS fell from 76 to 24, p < 0.005) but three were not satisfied (mean VAS 81). Eight of ten surgically treated patients were satisfied and back to their previous recreational or sport activity (their mean VAS fell from 75 to 21, p < 0.005) and two were not satisfied (one had a postoperative deep wound infection and the other had a VAS of 80).
In another randomised controlled trial, 31 patients with chronic (over 3 months) mid-portion Achilles tendinopathy (37 tendons), received “mini-open surgery” (the tendon was completely released from the ventral soft tissue by sharp dissection with a knife) or percutaneous scraping with a needle around the ventral tendon.42 There were no differences between the groups in terms of pain or patient satisfaction.
Limitations of the data
Although several non-operative and operative managements have been described, few randomised controlled trials have been published, and few patients have been included. Among conservative treatments, only eccentric exercises and ESWT are supported by high level scientific evidence.
What do guidelines say?
The National Institute for Health and Clinical Excellence (NICE) states that the current evidence on the efficacy of ESWT for refractory Achilles tendinopathy is inconsistent.24 Thus clinicians should ensure that the patient understands the uncertainty about efficacy of the procedure; inform the clinical governance leads in their Trusts; and carry out audit and a review of the clinical outcomes of the treated patients.24
Similarly, NICE states that current evidence on the safety and efficacy of autologous blood injection for tendinopathy is inadequate in quantity and quality; therefore, this procedure should only be used with special arrangements for clinical governance, consent and audit or research.43
More recent guidelines from the orthopaedic section of the American Physical Therapy Association state that there is strong evidence that clinicians should consider implementing an eccentric loading programme to decrease pain and improve function in patients with mid-portion Achilles tendinopathy.8 Based on moderate evidence, they recommend considering low level laser therapy.8 They also suggest that a foot orthosis can be used to reduce pain (based on weak evidence), and that night splints are not beneficial compared with eccentric exercises (based on weak evidence).8
Achilles tendinopathy is a frequent injury that may be associated with sport, or with systemic disorders, and a range of interventions has been suggested to manage the condition. However, there is limited evidence of benefit for many treatments. In sport-related tendinopathy, the first-line treatment should be physical therapy through an appropriately performed programme of eccentric exercises. There is insufficient evidence to recommend other conservative management options. In patients who fail to improve with non-operative treatments, surgery may be considered. Although no optimal surgical procedure has been identified, minimally invasive techniques may be associated with decreased peri-operative morbidity compared with open surgery.