Introduction & Diagnosis
What used to be known as Achilles tendinitis, Achilles tendinopathy is particularly common among middle-aged runners & those involved in jumping sports. In runners it has an annual incidence of 7% to 9%. It affects males more frequently than females. It occasionally afflicts sedentary individuals, particularly those with co-morbidities including obesity, diabetes and inflammatory arthropathies.
There are two classic forms, the mid-substance and the insertional types. While they may present similarly, the distinction between them is important when it comes to rehabilitation, as they will respond differently to exercise.
Symptomatology:
Pain and stiffness will often be worse after rest, particularly first thing in the morning. It will be present at the start of activity but settle after warming up. It will then often be worse after activity, and as the condition progresses pain may last throughout activity.
Signs:
Mid-substance tendinopathy is characterised by tenderness 2-6cm proximal to the Achilles insertion. With insertional tendinopathy the region of tenderness is over the posterior calcaneous. Strength testing will usually reveal decreased plantar flexor strength and .endurance
Differential Diagnosis:
While the clinical diagnosis is usually straight forward, other injuries to consider include 2:
1. Acute Achilles tendon rupture
2. Partial tear of the Achilles
3. Retro calcaneal bursitis. This will often co-exist with insertional tendinopathy.
4. Posterior ankle impingement.
5. Irritation or neuroma of the sural nerve.
6. Os trigonum syndrome
7. The presence of an accessory soleus. This is rare but occasionally responsible for persistent pain in the Achilles region.
8. Achilles tendon ossification
9. Plantaris tendinopathy.
10. Systemic inflammatory disease
Imaging:
This is rarely necessary, but may be helpful when the diagnosis not clear. MRI and ultrasound have similar reliability.
Examination:
Palpation of the area of tenderness is the key finding. Additional tests may include the one or two-legged hop test comparing sides, and a muscular endurance test such as the repetitive heel raise. When the diagnosis is unclear, tests should also be conducted to rule out other conditions listed above. Description of these tests is beyond the scope of this newsletter, however, the forced plantar flexion test can be helpful in excluding posterior impingement or os trigonum syndrome.
References:
1. Alfredson, H et al (1998). Heavy-load eccentric calf muscle training for the treatment of chronic Achilles tendinosis. AJSM, 26, 3, 360-366.
2. Carcia, C et al (2010). Achilles tendinopathy: clinical practice guidelines. JOSPT, 40, 9, A1-A26.
3. Sussmilch-Leitch, S et al (2012). Physical therapies for Achilles tendinopathy: a systematic review and meta-analysis. Journal of Foot & Ankle Research, 5, 15.
Anatomy & Pathology
Anatomy:
The Achilles tendon is the largest and strongest tendon in the body, and in adults is approximately 15cm in length. It is the conjoined tendon of the gastrocnemius and soleus muscles. It is wide and flat proximally, becomes rounded as it descends, and becomes flatter and wider again close to its insertion. In the transitional region from round to flat tendon, the collagen fibres twist 90°. Tendon fibres from gastrocnemius are situated more posteriorly and laterally, while those from soleus are relatively anterior and medial.
There is no synovial sheath surrounding the Achilles tendon. However it is contained within a ‘paratenon’, a single layer of fatty areolar tissue. This permits gliding of the tendon within its surrounding tissues, and provides a limited blood supply to the tendon. Blood vessels also enter at the musculotendinous junction, and the distal insertion. However the region of tendon 2 to 6 cm proximal to the calcaneus is relatively avascular. This, and the change in orientation of tendon fibres, may be factors in the development of mid-substance tendinopathy (see below).
Achilles tendinopathy is most prevalent in middle-aged and older individuals. It is associated with decreases in musculotendinous strength, endurance and plyometric ability. This is because the mechanical properties of the tendon are known to change with disease. Because the turnover rate of collagen decreases with increasing age, recovery in older people is likely to be slower.
Types of tendon pathology:
1. Mid-substance tendinopathy. 55 to 65% of cases of Achilles tendinopathy occur in the mid-portion. This is usually a persistent or chronic disorder associated with a degenerated tendon. It is considered to be non-inflammatory. There will be a palpable thickening 2-6cm above the heel, which moves with dorsi- and plantarflexion (unlike a paratenonitis – see below). On current understanding, the Achilles is the only region of the body where a true mid-substance tendinopathy occurs. The difference here is that there is no direct bony contact with the diseased area of tendon. While tendinopathy can occur in the mid-region of other tendons, - such as supraspinatus, psoas major, tibialis anterior, and peroneus longus - compression between tendon and bone is an important causative factor in these examples.
2. Insertional tendinopathy. The pathology associated with insertional Achilles tendinopathy has been found to be similar to that of mid-substance tendinopathy. That is, the process is one of degeneration rather than inflammation. However insertional Achilles is often associated with retrocalcaneal bursitis and sometimes with a Haglund’s deformity (see below). It is also more common in sedentary and obese individuals, unlike mid-substance tendinopathy which is more common in recreational and elite sportspeople. The mechanism is thought to be compression of the undersurface of the tendon against the calcaneal tuberosity. For this reason, the condition is more likely to be aggravated by uphill running and other activities that cause repeated or sustained ankle dorsiflexion.
3. Paratenonitis. This can occur in conjunction with tendinopathy. The paratenon surrounding the Achilles can become inflamed. This will result in diffuse tenderness and swelling on both sides of the tendon. There may be associated nodularity and crepitus. This is particularly common in middle and long-distance runners. It often results in swelling between the paratenon and tendon, which can be visualized and palpated. The area of swelling and tenderness typically remains fixed with ankle plantar- and dorsiflexion. Paratenon pathology may co-exist with degenerative tendon disease.
4. Retrocalcaneal bursitis. The retrocalcaneal bursa is a horseshoe-shaped bursa between the anterior Achilles and the posterior surface of the upper calcaneus. There will be pain and often swelling palpated anterior to the tendon. Like insertional Achilles tendinopathy, it will be exacerbated by activities that involve ankle dorsiflexion. The superficial bursa, which is posterior to the Achilles tendon, can occasionally become inflamed. However this is not as common as retrocalcaneal bursitis.
5. Haglund’s deformity. This is an abnormal prominence of the posterosuperior aspect of the calcaneal tuberosity. This deformity increases the risk of insertional Achilles and retrocalcaneal pathology, due to mechanical irritation. There is also a possibility that chronic insertional tendinopathy or bursitis may in turn lead to the development of the Haglund’s lump.
References:
1. Cook, J & Purdam, C (2009). Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load-induced tendinopathy. British Journal of Sports Medicine, 43, 409-416.
2. Heckman, D et al (2009). Tendon disorders of the foot and ankle, part 2: Achilles tendon disorders. AJSM, 37, 6, 1223-1234.
3. Jonsson, P et al (2008). New regime for eccentric calf muscle training in patients with chronic insertional Achilles tendinopathy: results of a pilot study. British Journal of Sports Medicine, 42, 746-749.
Risk Factors for Achilles Tendinopathy
Risk Factors for Achilles Tendinopathy
Extrinsic Factors:
1. Overload due to increased, altered or incorrect training stimulus.
2. Faulty equipment / footwear
3. Running technique. While the ideal running style will depend on several factors, there is preliminary evidence that a rearfoot strike pattern may load the Achilles significantly less than a forefoot or even midfoot strike pattern.
4. Environmental factors. The type of training surface will influence tendon loads. It has been found that a firmer or stiffer running surface may reduce the injury risk. A military study showed recruits were more likely to develop tendinopathy during the winter months.
Intrinsic factors:
Studies have found the following factors to be associated with greater risk:
1. Age. Tendinopathy is more prevalent in middle-aged and older individuals. Healing time will increase with advancing age.
2. Abnormal dorsiflexion (particularly decreased) range of motion.
3. Increased or decreased subtalar pronation.
4. Reduced calf strength or endurance.
5. Co-morbidities including obesity, hypertension, increased cholesterol, diabetes, and systemic inflammatory arthropathies, particularly rheumatoid and psoriatic arthritis.
Interventions for Achilles Tendinopathy
Exercise
1. Exercise has consistently been shown to be the gold standard treatment for Achilles tendinopathy. However, it is important for practitioners to understand and educate their patients regarding the realistic healing timeframes involved. While other musculoskeletal tissues such as bone, ligament and muscle, may be expected to heal over 6 to 12 weeks, the healing time for tendon is considerably longer. Depending on age, tendon pathology and intrinsic influences, the patient may be faring well with recovery over 3, 6 or even 12 months. In past years, it has been customary for experts to recommend 3 months of conservative management before consideration of surgical intervention. In most instances of tendon healing, this is an unreasonable expectation.
The best form of exercise will depend on the stage, type and severity of the disease. Very broadly, moderate to heavy isometric exercise often forms a ‘base’ from which to start and progress the strengthening programme. In many instances this has been found to provide very effective analgesia, and well as a safe early training load. Tendinopathy is known to be associated with cortical muscle inhibition. Isometric exercise has been found to significantly reduce intracortical inhibition, and this may be related to the mechanism for pain relief. These exercises can generally be performed daily, and are often recommended to be performed up to several times per day.
More recently, there has been increasing research into heavy slow resistance training. While not so effective for pain relief, this training method has been found to be effective in improving function and strength, particularly in medium to later stage rehab. Due to the physiological effects of such loads on collagen, namely a net decrease in strength and structure over 24 to 36 hours, such exercises might only be performed twice weekly in the early stages. The frequency is progressed as function and strength improves.
Speed is another consideration when prescribing exercise. Tendon load is increased substantially when increasing the speed of contraction. So training for speed and power is addressed towards the later stages of rehab.
Kinetic chain strength is addressed throughout rehab, and particularly before return to sport. It is known that several muscle groups throughout the lower limbs will be adversely affected with localised tendinopathy. It will be insufficient to target only the Achilles in the strength programme.
(a) Mid-substance Achilles tendinopathy: Several studies have shown heavy, full-range eccentric strengthening (e.g. weighted heel lowering off a step) to be extremely effective for the treatment of mid-substance tendinopathy. However, more recent research has shown that eccentric training is only one component of overall strengthening. Functional recovery is reliant on restitution of musculotendinous isometric and concentric/eccentric force generating capacity. And strengthening for power and throughout the entire ‘kinetic chain’ is an essential component of overall management.
(b) Insertional Achilles tendinopathy: This condition also responds well to exercise. However in the early and intermediate stages of recovery, full range loading and even passive calf muscle stretching is usually contraindicated for insertional Achilles tendinopathy. This is because of the significant causative role in the disease played by bony compression on the undersurface of the Achilles. Modified exercise that controls for this compressive loading has been shown to be very effective in treating insertional Achilles pain. This usually involves avoiding or minimising dorsiflexion past plantargrade until later stage recovery.
Following recovery & return to sport, an Achilles maintenance programme is recommended to be continued for at least one sporting season.
Shock Wave Therapy (SWT)
Also known as extracorporeal shock wave therapy, this is applied via a mechanical device that somewhat resembles an ultrasound machine. Shock waves are abrupt, high amplitude pulses of mechanical energy. This is applied directly to the painful area of tendon, where it is proposed a healing response is stimulated. There is a degree of discomfort associated with the treatment. The results of studies are equivocal. For Achilles tendinopathy, two studies found it to be no more effective than a sham intervention (cited in Sussmilch-Leitch, et al).
Laser Therapy (LT)
Like SWT, most RCT studies have looked at the effectiveness of LT in combination with exercise. There is evidence that these interventions combined are an effective treatment for Achilles tendinopathy. No quality studies have reported the effect of LT in isolation for this condition.
Injections
Cortisone injections are not recommended for any Achilles related condition, including tendinopathy, paratenonitis or bursitis, due to the adverse effects on the mechanical properties of the tendon (Dean et al 2014; Heckman et al 2009), and the significantly increased risk of tendon rupture (Heckman et al 2009). The next newsletter will provide a more detailed overview of injection therapies for Achilles tendinopathy.
A discussion of surgical intervention for the management of recalcitrant Achilles tendinopathy is beyond the scope of this newsletter.
References:
1. Alfredson, H et al (1998). Heavy-load eccentric calf muscle training for the treatment of chronic Achilles tendinosis. AJSM, 26, 3, 360-366.
2. Carcia, C et al (2010). Achilles tendinopathy: clinical practice guidelines. JOSPT, 40, 9, A1-A26.
3. Cook, J et al (2016). Revisiting the continuum model of tendon pathology: what is its merit in clinical practice and research? British Journal of Sports Medicine, 50, 1187-1191.
4. Cook, J & Purdam, C (2009). Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load-induced tendinopathy. British Journal of Sports Medicine, 43, 409-416.
5. Dean, B et al (2014). Glucocorticoids induce specific ion-channel-mediated toxicity in human rotator cuff tendon: a mechanism underpinning the ultimately deleterious effect of steroid injection in tendinopathy? British Journal of Sports Medicine, 48, 1620-1626.
6. Heckman, D et al (2009). Tendon disorders of the foot and ankle, part 2: Achilles tendon disorders. AJSM, 37, 6, 1223-1234.
7. Jonsson, P et al (2008). New regime for eccentric calf muscle training in patients with chronic insertional Achilles tendinopathy: results of a pilot study. British Journal of Sports Medicine, 42, 746-749.
8. Magnusson, R et al (2009). Non-operative treatment of midportion Achilles tendinopathy: a systematic review. Clinical Journal of Sports Medicine, 19, 54-64.
9. Rio, E et al (2015). Isometric exercise induces analgesia and reduces inhibition in patellar tendinopathy. British Journal of Sports Medicine, 49.19,1277-1283.
10. Silbernagel, K & Crossley, K (2015). A proposed return to sport programme for patients with mid-portion Achilles tendinopathy: rationale & implementation. JOSPT, 45, 11, 876-886.
11. Silbernagel, K, et al (2011). The majority of patients with Achilles tendinopathy recover fully when treated with exercise alone: a 5 year follow-up. AJSM, 39, 3, 607-613.
12. Stanish, W. et al (1986). Eccentric exercise in chronic tendinitis. Clinical Orthopaedics & Related Research, 208, 65-68.
13. Sussmilch-Leitch, S et al (2012). Physical therapies for Achilles tendinopathy: a systematic review and meta-analysis. Journal of Foot & Ankle Research, 5, 15.
Recent History of Tendinopathy Research
Two famous research papers have laid the platform for a vast improvement in the way tendon disease is managed. Both studies examined the value of exercise in treating chronic Achilles tendinopathy:
Stanish et al in 1986 were the first authors to introduce the concept of eccentric exercise to promote tendon healing. They recognized that physiologically, eccentric (lengthening) muscle contraction forces may exceed concentric (shortening) and isometric (static) contraction forces up to threefold. They theorized that such forces would more successfully stimulate adaptation. The same authors also discussed the negative effects of rest and immobilization on bone, muscle, tendon and ligamentous tissues. For instance, it was found that normal primate ligaments when immobilized for 8 weeks, took 12 months to regain normal strength. Immobilization had long been advocated for painful tendons, and even today this is frequently prescribed. However immobilization is almost certainly counter-productive and most likely harmful to the tendon.
Other important strengthening concepts discussed by these authors included progressive load, and the speed of muscle contraction. Increasing speed greatly increases force development, and is one of the important late stage (e.g. prior to return to sport) training considerations.
The authors proposed that not only was pain allowed during exercise rehabilitation for tendon disease - it was considered to be essential. In their study, 200 patients with chronic tendinopathy (mean duration 18 months) were placed on an eccentric strengthening
programme, performed over 6 weeks. 87% of subjects had complete or near complete reduction in pain and return to normal function. The mean follow-up was 16 months.
Alfredson et al in 1998 published their study on heavy load eccentric training for chronic Achilles tendinopathy. They acknowledged the work of Stanish et al, but reported that prior to 1998 there had been no prospective studies on this training method.
15 recreational athletes (12 males) with symptoms of mid-substance Achilles tendinopathy present a minimum of 3 (and up to 100) months (mean 18 months) had been placed on a surgical waiting list. They were given twice daily eccentric exercises consisting of both straight and bent-knee calf raises. The load was progressively increased using a weighted back pack.
At 3 months all patients had full or significant relief of symptoms, and return of full strength and function. None required surgery. They were compared to 15 matched patients who underwent surgery. The surgical group took twice as long for symptoms to abate, and still had significant strength deficits at 6 months.
For over a decade following the Alfredson paper, eccentric loading became the standard management for all forms of tendinopathy. However equivocal results led to a re-think, and a tremendous amount of further research. Recent work by Cook and Purdam has been at the forefront of this research. It became apparent that not only were there different stages and types of tendon disease within each tendon, such as the Achilles, but also different responses dependent to the anatomical location in the body. There has been a dramatic change in the way exercises are prescribed, and a recognition that purely eccentric training is sometimes harmful, and only part of the training load stimulus necessary for optimal functional recovery. A complete training regime will include isometric, concentric and eccentric loading, as well as dynamic and kinetic chain (the body as a whole) functional strengthening.
References:
1. Alfredson, H et al (1998). Heavy-load eccentric calf muscle training for the treatment of chronic Achilles tendinosis. AJSM, 26, 3, 360-366.
2. Cook, J et al (2016). Revisiting the continuum model of tendon pathology: what is its merit in clinical practice and research? British Journal of Sports Medicine, 50, 1187-1191.
3. Cook, J & Purdam, C (2009). Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load-induced tendinopathy. British Journal of Sports Medicine, 43, 409-416.
4. Stanish, W. et al (1986). Eccentric exercise in chronic tendinitis. Clinical Orthopaedics & Related Research, 208, 65-68.
