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Tendon Injury Rehabilitation Under Review

Usian Bolt

Usian Bolt has a fantastic ability to absorb and release energy through his Achilles tendon, but the extra load increases the risk of injury. Source: Wikimedia Commons

By Peter Malliaras

A review finds poor evidence for a common rehabilitation intervention used by physiotherapists to treat tendon injuries.

Most people that suffer a tendon overuse injury are prescribed exercise as part of their treatment. Over the past 15 years the most popular form of exercise that clinicians prescribe has been “eccentric” exercise. This is where the muscle is loaded while it is lengthening, such as the downwards phase of a biceps curl. In contrast, “concentric” exercise is where the muscle shortens while under load, such as the upwards phase of a biceps curl.

Experts in the field know that eccentric exercise is not the only way to rehabilitate tendons, and in some cases other types of exercise may be more beneficial. Now, a review published by an international research group in Sports Medicine, the highest ranking journal in the field, has questioned the value of eccentric exercise for Achilles and patellar tendon injuries.

We undertook a systematic review of evidence comparing this approach to other rehab approaches, and found no compelling evidence for its superiority. In fact, there was equal or higher level evidence for other forms of exercises. The review provides convincing evidence that clinicians should consider other forms of exercise when rehabilitating tendon overuse injury.

Tendinopathy

Painful overuse injuries are common in tendons that endure high forces, such as the Achilles and patellar tendons. These injuries have a gradual onset without incident, but can make it very difficult to perform simple activities such as walking and climbing stairs, as well as sporting activities.

Many athletes have to take extended periods of time of away from sport or go to extraordinary lengths to overcome these injuries. It is well documented that Rafael Nadal has suffered bouts of left knee patellar tendinopathy, necessitating extended periods away from tennis.

Previously this type of injury was known as “tendinitis” – the itis suffix suggesting an inflammatory pathology. However, researchers have known for decades that longstanding tendon pain may not be inflammatory, so the conventional term is now “tendinopathy”.

The pathology that is seen in laboratory studies is effectively a failed response of the tendon to adapt to forces placed on it during daily activities and sport. Tendons contain very well-organised collagen that resists tensile or pulling forces. In fact, the ability of tendons to resist pulling forces is greater than any other tissue in the body, including bone.

However, in cases of tendinopathy the organisation of this tissue is impaired. We see poorer quality collagen that weakens the tendon and increases the risk of pain and rupture.

There seem to be an order to the pathology changes we see in tendon injuries. In an earlier study of volleyball players we noticed a temporal sequence in the pathology of the patellar tendon. Ultrasound imaging over the course of a season revealed that many of the volleyball players went in and out of very mild pathology changes. One month their patellar tendon could appear normal, the next it could be mildly thickened, and then the next it could be normal again. This may be part of a normal adaptive response to load.

We also saw more severe tendon injuries. These were less common, and when they did occur people almost never regained normal tendon structure. Hence severe tendon pathology does not seem to be reversible, much like an arthritic lesion in the knee. However, we know that pain is often intermittent in tendon injury and arthritis, so the pain and pathology mechanisms are separate.

So why are these injuries so difficult to overcome? We know that tendons are slow and sluggish tissues to adapt and develop in response to our activity. They have been much maligned in clinical circles for having a poor blood supply; if you have consulted someone with tendon pain they have probably mentioned this, but the reality is that they have a very low metabolic rate so they can afford to have a low blood flow.

Tendon Loading

The issue for tendons is when we perform an activity that is out of the ordinary. This stresses tendon tissue as it doesn’t have the blood flow and infrastructure to deal with sudden changes in activity. So the problem we face is more about the gap between what our tendons have evolved to do and the stresses we place on them in modern life.

The type of load that stresses tendon is impact load, as in jumping and running, because the tendon acts as a spring and absorbs energy. This makes our movement more efficient and can also make us perform better.

For example, Usain Bolt has a fantastic ability to absorb and release energy through his Achilles tendon in sprinting, and this enhances his performances. The flip side is he has an increased risk of injury because he loads the Achilles tendon heavily when he uses it as a spring.

We all use our Achilles and other tendons in the lower limb as springs whenever we walk, so this high load tendon function is not just seen in sportspeople. The fact that tendons absorb energy in walking is why we see so many tendinopathies in patients whose only exercise is walking.

The other type of load that tendons do not respond well to is compressive load. This occurs where the tendon and bone join, and is where we see a majority of tendon injuries. Tendons have a well organised collagen structure that is not well suited to taking compressive loads. Part of the pathology is a build-up of cartilage-like molecules that bind water. This is actually what causes tendon swelling – the lump in the middle of the Achilles that you often see in cases of Achilles tendinopathy.

A sluggish or failed response to load is compounded among people who have systemic issues. There are links between tendon injury and reduced oestrogen in women at menopause and even women who have early hysterectomies or do not have a regular menstrual cycle. The mechanisms are not clear but oestrogen may be involved in tendon metabolism. There are also strong links between lipid or cholesterol issues and tendinopathy. There are many other potential systematic risk factors, such as genes and age, that not only contribute to tendon injury but also prolong recovery.

As a clinician who specialises in tendinopathy cases, I see many patients who have tendon pain that has a large systemic component. On the whole these patients tend to be much more difficult to manage as they do not respond as well to tendon loading exercise, the key intervention that we use to manage tendon injury.

Common Treatments

It is generally accepted that the key treatment for tendinopathy is exercise – the only intervention that can restore a painful tendon’s ability to take the loads that it needs to in everyday function and sport. A simple formula that I use in clinical practice is to consider the loads that a patient needs to endure in their day-to-day function and then design an exercise program that progressively allows them to endure these loads without the tendon becoming painful.

The key is to make sure that exercise is commenced at a level that will not cause the tendon to become irritable, and that it is progressed at a rate that the tendon can tolerate. Every patient that I see is different, and how they progress with their rehabilitation depends on many individual factors, including musculo­skeletal, systemic, motivational and psychological factors.

Table 1

There are many other treatments used to treat tendinopathy (Table 1). When in a very painful phase, with symptoms constant and interrupting everyday activities, the main treatment is rest from aggravating activity, ice and manual therapies like massage and other modalities like acupuncture, braces and tapes to reduce the load on painful tissues. Oral anti-inflammatory medications and steroid injections are used when initial interventions fail to settle the pain.

When pain has settled, the main treatment is exercise to restore the tendon’s ability to withstand the loads placed upon in by daily function and sport. Common adjunct treatments in this phase are shockwave therapy and blood or platelet-rich plasma injections but unfortunately the evidence base is still very limited for most of these interventions. Shockwave therapy is a mechanical treatment that was originally used to break apart kidney stones. It was then used to break up small areas of bone growth that are common in tendon pathology and more recently we have used shockwave with many tendon patients to modulate pain.

Eccentric Exercise

Over the past 10–15 years a form of exercise referred to as eccentric training has become the most popular treatment for Achilles and patellar tendinopathy. A vast majority of Achilles tendinopathy sufferers would have had the experience of being prescribed exercises where they stand half-way off a step and slowly lower their bodyweight. The calf muscle controls the movement while it is stretched, and this is an eccentric contraction.

In the reverse movement – lifting the bodyweight up by lifting the heel – the muscle shortens and this is referred to as a concentric contraction. Eccentric muscle actions tends to feel easier, much like benchpressing where pushing the weight away from your chest is much harder than controlling the weight while lowering it towards your chest.

One theory about how eccentric training works as a treatment for tendinopathy is that it can be progressed faster because it is easier, so the muscle and tendon adapt faster. Regardless of the mechanisms, eccentric training has spread like wildfire and people around the world with tendon pain are most likely familiar with this exercise.

While there are studies supporting eccentric training to treat Achilles and patellar tendinopathy, some studies are poor quality and not all patients get better. Recently, I was part of an international group of researchers and expert tendinopathy clinicians who published a review that challenges eccentric training as the best treatment for Achilles and patellar tendinopathy. There were four studies that compared loading programs in the Achilles and six in the patellar tendon. Only two studies were rated as high quality.

The most surprising finding was that very few studies have actually compared eccentric training to other forms of exercise. For example, only one study had compared eccentric training to another form of exercise in the Achilles tendon.

Overall, there was no evidence that eccentric training is better than other exercise in treating these injuries. In fact, there was equivalent (Achilles tendon) or more evidence (patellar tendon) to support exercise that involved both eccentric and concentric contractions in combination.

I see mainly second opinion tendinopathy cases, and one of the most common reasons they have not improved with eccentric loading is that they have marked weakness of their concentric function. Due to a very well-established principle known as “specificity in exercise”, people will tend to get better at the type of exercise they do. So, I always combine eccentric and concentric loading for patients with concentric weakness.

This is a novel and important message for patients with tendinopathy and clinicians treating this injury. It goes some way towards toning down the current belief among some clinicians that eccentric training is an all-conquering panacea for treating tendon injury.

This is common in when clinicians are starved of evidence and understandably embrace limited or poor quality research and apply it inappropriately. The future challenge in tendinopathy rehabilitation is to increase the evidence base, individualising exercise interventions rather than adopting a one-size-fits-all approach.

Peter Malliaras (peter@completesportscare.com.au) is a physiotherapist and tendinopathy clinician-scientist who consults at Complete Sports Care in Hawthorn. He is a Visiting Senior Lecturer and Honorary Researcher at the University of Melbourne and Queen Mary University of London, and Director of Research at Imaging @ Olympic Park in Melbourne.