Risk factors in tendinopathy



Tendinopathy has a multifactorial etiology that is not well understood. Risk factors are often separated into extrinsic factors, so those acting on the body from the outside and intrinsic factors, so all factors acting from within the body. In their narrative review, Peter Malliaras & Seth O'Neill (2017) discuss 3 different classes of risk factors. They are looking at:

1) Load-related (extrinsic) factors

2) Biomechanical (intrinsic) factors

3) Other individual and systemic factors (which can be classified as intrinsic) as well.


Load-related extrinsic factors

Figure from Komi et al. (2000)

1) Load: Stretch-shorten cycle loads        

Repetitive stretch-shortening cycles of the muscle tendon unit such as walking and running for Achilles tendinopathy or jumping for patellar tendinopathy are associated with tendinopathy. The tendon load may only be able to explain part of the story.  In running and submaximal hopping the Achilles tendon load is reported to be 6-8 times and 8-10 times bodyweight respectively, while the load during maximal isometric plantar flexion contraction is only 3.5 times bodyweight.
On the other hand, the load on the patellar tendon during squatting is similar to a spike jump take off with 4.8 times bodyweight and 5.2 times bodyweight respectively. The crucial difference between fast+high load activities and slow +high load activities like in rehab is the tendon strain rate. While in squatting it is about 1-2 times bodyweight per second, it is as high as 40 times bodyweight per second in a spike jump take off. This probably explains why tendinopathy is associated with repetitive stretch-shortening cycles while slow and heavy loading is not.


2) Compression:

A classic study by Soslowky et al. (2002) manipulated mice so that one group had an enlarged acromial roof (group E), another group was overloaded by downhill running (group OV) and a third group had both external compression and overload combined (Group OVE/E). The results of that trial showed that compression alone did not lead to pathology, but a combination of compressive and tensile loads was more damaging than tensile loads alone.


3) Change in load

The most common cause for tendinopathy are training errors involving sudden changes in load. This encompasses any fluctuations in intensity, frequency, or duration of exercise or a combination of all three. For this reason, tendinopathy is often seen in athletes in pre-season after a holiday break. Like mentioned before, important is a change in energy storage type of loads as they stress the tendon the most. When taking patient history in patients in who you suspect tendinopathy ask for hill or speed sessions, marathon or similar events, if they have bought a sports watch or Fitbit which motivated them to push harder, preseason breaks or a change in shoes or training surface


4) Load parameters

Higher Load duration, intensity and frequency are associated with  with patellar pain and Achilles tendinopathy. This fits the evidence of Magnussen et al. (2010) who have found that repeated intense loading without sufficient recovery may be a risk factor for tendon pathology. Be aware, that this association is not consistent however and that a change in load may be a confounder in this relationship.


5) Biomechanical and neuromuscular factors (intrinsic factors):

Individual biomechanics, including movement kinetics and kinematics, foot posture, flexibility, neuromuscular capacity and structural anatomy may influence tendinopathy risk. However, the relationship between biomechanics and the development of tendinopathy is a mess. If you want to have a look at individual articles, we are highly recommending to you to start with this narrative review of Malliaras & O'Neill (2017).
In general, it seems that extremes in biomechanics might be risk factors worth paying attention to during rehab. For example, both increased and decreased dorsiflexion are described as risk factors in the development of Achilles tendinopathy. The same is true for increased as well as decreased hamstring flexibility for patellar tendinopathy.

The link between neuromuscular changes and pain is even less clear. Comparable to other body regions and pathologies cross-sectional students don’t allow us to say if neuromuscular impairments such as decreased strength are a consequence of pain or if they are a risk factor leading to tendon pain.
For our rehab, this means the following: while a good loading program is necessary for all patients, interventions to target biomechanical factors and neuromuscular changes might be necessary for some patients who are at the extreme ends of the spectrum. Similar to other body regions and with all the individual variation in posture and movement between individuals it’s difficult to really say which posture or movement is “faulty”.
At last, if we do assume to have found a biomechanical or neuromuscular factor the question is if we are able to change those factors by therapy.


6) Individual and systemic factors (intrinsic factors):
Multiple systemic factors have been linked with tendinopathy including age, high cholesterol, adiposity and genetics. These systemic risk factors are thought to reduce the capacity of the tissue to tolerate load, gradually altering tendon capacity so that an extra walk, a quick dash across the road, or a day spent gardening may be sufficient to overload the tendon triggering symptoms. Systemic factors might also play a greater role in case of bilateral involvement or in tendinopathy where load seems to play a smaller role such as in pes anserinus tendinopathy.  Furthermore, these systemic factors combined with biomechanics might be able to explain why under similar loading conditions some athletes develop tendinopathy and others don’t. Finally, cognitive and emotional factors such as anxiety, illness beliefs and fear-avoidance behavior can influence a person’s pain experience and should not be disregarded.
The envelope of function by Scott Dye beautifully summarizes the risk factors involved in the etiology of tendon pain:

So the envelope of function is the load/frequency distribution defines the safe or homeostatic range of load acceptance. So if the combination of load and frequency exceed your envelop of function it will lead to pathology. It’s also interesting to see that suboptimal loading may lead to disuse effects, which we know is especially a problem in tendons. Peter Malliaras adds that biomechanics can directly influence the load in this graph.

On the side systemic and individual factors will all have an influence on an individual propensity to develop pain.

Alright, this was our blog on risk factors for tendinopathy. We hope you enjoyed reading it! If you love tendons and would like to learn more about the topic, check out our video on 7 absolutely crucial facts about tendon you didn’t know. As always, thanks for reading! Physiotutors



Magnusson SP, Langberg H, Kjaer M. The pathogenesis of tendinopathy: balancing the response to loading. Nature Reviews Rheumatology. 2010 May;6(5):262.

Malliaras P, O’Neill S. Potential risk factors leading to tendinopathy. Apunts. Medicina de l'Esport. 2017 Apr 1;52(194):71-7.

Soslowsky LJ, Thomopoulos S, Esmail A, Flanagan CL, Iannotti JP, Williamson JD, Carpenter JE. Rotator cuff tendinosis in an animal model: role of extrinsic and overuse factors. Annals of biomedical engineering. 2002 Sep 1;30(8):1057-63.


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Pathomechanics of lower limb muscle and tendon injuries

Isometrics in tendinopathy – a wonder weapon to decrease pain?

Isometrics in tendinopathy – a wonder weapon to decrease pain?

Are isometrics the wonder weapon to decrease pain in tendinopathy? In this blog we will discuss where the isometrics “trend” came from and what the evidence says about it!

In 2015 Dr. Ebonie Rio and colleagues started a bit of trend when they conducted a cross-over trial in 6 volleyball players with patellar tendinopathy. Their results were astonishing with all players experiencing an immediate decrease in pain from an average of 7/10 on the NRS to 0 with only one of the 6 reporting a remaining pain of 1– for at least 45 minutes after the isometric contractions.The protocol they used were 5 sets with 45 seconds contraction in a leg extension machine and an effort of 70% of the maximal voluntary effort. They also found that isometrcis were able to decrease cortical inhibition and an increase in strength of 19%.They compared the isometric intervention with an isotonic intervention and the effects seen in the isometric group could not be achieved in the isotonic group:

Figure from Rio et al. (2015)

The same authors did a follow up in-season study with jumping athlets two years later in which they compared an isometric programme and an isotonic programme to each other. In this study the results were a bit more heterogenous with both groups with a greater immediate pain decrease in the isometric group:

Figure from Rio et al. (2017)

A recent study by Holden et al. (2019) looked at the effect of isometrics in patellar tendinopathy as well and did not find any analgesic effect:

Holden et al. (2019)

However, a high percentage of women and a relative high average age is untypical for patellar tendinopathy, which is usually a disease of young jumping men. So it could be that the diagnosis of patellar tendinopathy was no correct in some cases.
Now while those two studies were conducted for patellar tendinopathy, let’s look if we can transfer these results to other tendons.
Looking at the Achilles tendon, Seth O’Neill and colleagues did a study in 2018 in which they had a group of patients with Achilles tendinopathy performing isometric contractions of the plantar flexors. They found no immediate pain relief nor improved motor output in patients with Achilles tendinopathy:

Figure from O'Neill et al. (2018)

A study of Riel et al. In the year 2018 examined the effects of isometrics, isotonics and walking on pain for plantar fasciitis. They found that there was no change in pain for any of the groups before to after the exercises:

Riel et al. (2019)

At last, Coombes et al. In the year 2016 looked at isometrics on lateral epicondylalgia. In their study, isometric contractions above the patients’ pain threshold actually increased their pain levels after the exercise, while isometric contractions below the patients’ pain threshold had no effect compared to a control group:

Figure from Coombes et al. (2016)

Another study from Stasinopoulos et al. In the year 2017 compared three exercise groups in the treatment of lateral epicondylalgia: One group performed eccentric training, another eccentric-concentric training and the third group combined eccentric-concentric training with isometrics. The authors argued that most grip activities require isometric contraction of the wrist flexors and extensors, so adding isometric exercises for LE makes absolute sense. They found that adding concentric led to superior results at pain, function and grip strength at 4 and 8 weeks:

Table from Stasinopoulos et al. (2017)

However, the follow up time of the study was rather short and should at least have been 12 weeks. On top of that the combined isometrics group performed a higher exercise volume with more time under tension which could explain the superior results.

So while isometrics are certainly no magic bullet, what role do they play in tendinopathy rehab? First of all,  isometrics are a great option to start exercising if everything else is too painful – and this is not only limited to tendinopathy but other conditions as well. Be aware that they must progress to isotonic exercises, because you want to recover muscle function over the full range of motion instead of just 1 angle. So move on as soon as a patient is able to tolerate isotonic loads.
What can be derived from all of those studies is that isometrics do seem to work really well in some subjects and can actually make things worse in other subjects. To keep it simple, give them a try with the patient in front of you and if they respond favourably, keep doing them, if they don’t move on.
While 45 minutes of pain relief might not be a goal that is important in the average patient, this might be useful for athletes as a warm-up to decrease pain during the ensuing exercise session or competition. Isometrics are also less tiring for athletes in-season as they are less tiring than isotonic exercises. One can surely argue if it is desirable to achieve short-term pain reduction in order to load a painful tendon during sporting activities and if this might actually lead to detrimental effects.

Alright, this was our blog on isometrics for tendinopathy. If you were surprised by the results, you will love our blog on 7 facts about tendinopathy you didn’t know! Thanks so much for reading. 



Coombes BK, Wiebusch M, Heales L, Stephenson A, Vicenzino B. Isometric exercise above but not below an individual’s pain threshold influences pain perception in people with lateral Epicondylalgia. The Clinical journal of pain. 2016 Dec 1;32(12):1069-75.

Holden S, Lyng K, Graven-Nielsen T, Riel H, Olesen JL, Larsen LH, Rathleff MS. Isometric exercise and pain in patellar tendinopathy: A randomized crossover trial. Journal of Science and Medicine in Sport. 2020 Mar 1;23(3):208-14.

O’Neill S, Radia J, Bird K, Rathleff MS, Bandholm T, Jorgensen M, Thorborg K. Acute sensory and motor response to 45-S heavy isometric holds for the plantar flexors in patients with Achilles tendinopathy. Knee Surgery, Sports Traumatology, Arthroscopy. 2019 Sep 1;27(9):2765-73.

Rio E, Kidgell D, Purdam C, Gaida J, Moseley GL, Pearce AJ, Cook J. Isometric exercise induces analgesia and reduces inhibition in patellar tendinopathy. British journal of sports medicine. 2015 Oct 1;49(19):1277-83.

Rio E, Van Ark M, Docking S, Moseley GL, Kidgell D, Gaida JE, Van Den Akker-Scheek I, Zwerver J, Cook J. Isometric contractions are more analgesic than isotonic contractions for patellar tendon pain: an in-season randomized clinical trial. Clinical Journal of Sport Medicine. 2017 May 1;27(3):253-9.

Silbernagel KG, Vicenzino BT, Rathleff MS, Thorborg K. Isometric exercise for acute pain relief: is it relevant in tendinopathy management?.

Riel H, Vicenzino B, Jensen MB, Olesen JL, Holden S, Rathleff MS. The effect of isometric exercise on pain in individuals with plantar fasciopathy: a randomized crossover trial. Scandinavian journal of medicine & science in sports. 2018 Dec;28(12):2643-50.

Stasinopoulos D, Stasinopoulos I. Comparison of effects of eccentric training, eccentric-concentric training, and eccentric-concentric training combined with isometric contraction in the treatment of lateral elbow tendinopathy. Journal of Hand Therapy. 2017 Jan 1;30(1):13-9.


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Pathomechanics of lower limb muscle and tendon injuries
7 crucial facts about lower limb tendons


7 crucial facts you didn’t know about tendons

7 crucial facts about lower limb tendons

In this blog post we are going to discuss 7 absolutely crucial facts about tendons that you probably didn’t know, but that are very important to improve your tendinopathy rehab.

Let’s jump right into it:

1. The nociceptive driver of pain in tendons is unknown. Pathology seen on imaging is not the driver of pain. Vascularity is not the source of pain, merely a marker of tendon degeneration. On top of that, there are no sensory nerves deep in the tendon, but in the periphery around the tendon. Nerves that grow into a pathological tendon, are sympathetic nerves, not sensory. At last, central sensitization is probably less a problem in lower limb pathology compared to upper limb pathology (Plinsinga et al. 2015, Plinsinga et al. 2018).


2. We are not able to repair/heal degenerative tendon pathology. In other words, no surgery, no shockwave therapy, no injections whatsoever and not even exercise is able to repair or heal a degenerated tendon. Docking et al.(2019) reason that with little ability to sense tensile load, the cells in the degenerative part of the tendon may be under-stimulated and not receive the necessary mechanical stimuli to remodel, explaining the limited capacity of the pathological tendon to remodel and normalize. While you think that this might be bad news, the good news is: it’s also not necessary. A study by Tsehaie et al.(2017) showed that 24 weeks of eccentric exercises for the Achilles tendon did not produce changes outside the limits of detectable change in the tendon, but yet patients improved. They also found that o MRI parameter at baseline predicted the change in symptoms, so even if your MRI looks terrible, it doesn’t matter.

Figure from https://www.ultrasoundcases.info/partial-ruptures-7335/#gallery-2


3. The tendon loading rate probably explains why tendinopathy is associated with repetitive stretch-shorten cycle (SSC) rather than heavy loads. The SSC occurs during any activity that requires the tendon to store and release energy like a spring. Everything else is easy for a tendon e.g. eccentric movements, high weight. The loading rate is calculated in BW/sec. Here are two examples for the patellar and the Achilles tendon in different activities. So the highest loading rate for the patellar tendon is to land in a stop jump sequence, like in a basketball or volleyball, while leg pressing 3x bodyweight has a very low loading rate. This is the same for the Achilles tendon where calf raises have a very low loading rate for the tendon while running and hopping have a very high strain rate. Interestingly, the very best athletes who can run fast or jump high are the ones who are also at risk to develop tendon pathology the most, probably because they can load their tendons faster than anyone else. This phenomenon is also called the “Jumper’s knee paradox”, described in an article by Visnes et al. (2013)

Patellar tendon tensile load and loading rate in typical activities:

Figure from a presentation of Jill Cook

Achilles tendon tensile load and loading rate in typical activities:

Figure from a presentation of Jill Cook

4. The Combination of compressive loads and tensile loads are more damaging to any of the two alone. A study by Soslowsky et al. (2002) compared 3 groups of mice to each other: In 1 group they manipulated the acromial arch to simulate external compression, one group had higher tensile loads as they had to run on a treadmill more than other groups and a combined group. They found that extrinsic compression did not cause injury until overuse activity was introduced. While compressive properties may be important, tensile properties are more relevant properties in a tissue such as a tendon. The results show that the combination of external compression plus tensile loads led to the greatest injury.

Figure from Soslowksy et al. (2002): Injury created by overuse plus extrinsic compression is greater than the injuries created by overuse or extrinsic compression alone. Significant differences relative to control are indicated by a ‘‘*’’ inside each bar (average +- standard deviation). Significant differences between single factors (E=Extrinsic, OV=Overload and multiple factors (OV/E) are indicated by a ‘‘*’’ above each pair of bars.

5. Intense loading of tendons results in net collagen degradation for up to 36h. A study by Magnussen et al.(2010) showed this effect in three groups of very intense exercise, which were 36km of running, 1 hour of repetitive kicking and 10 sets of 10 repetitions of knee extension at 70% maximal voluntary contraction. This means that we need sufficient recovery time to prevent tendinopathy and it’s advisable to space out training sessions for the tendon to every other day or less.

Figure from Magnussen et al. (2010)

6. A pathological tendon has more good structure than a normal tendon (Docking et al. 2015). This means we can load these tendons because we have loads of good tissue. Any therapies for tendon pathology are not necessary, because we cannot change the structure of the pathological part anyways. For this reason, Docking and colleagues came up with the quote “Treat the donut, not the hole” – in other words, focus on the healthy structure and not the pathological part.

Figure from Docking & Cook et al. (2015)


7. 66% of Achilles tendon ruptures are asymptomatic ruptures (Kannus et al. 1991). This means these people never had Achilles tenderness, stiffness, pain or dysfunction. However, there had to be some kind of pathology present in the tendon as the authors showed that 98% of ruptured tendons had degenerative pathology, while 2% had other pathology. Jill Cook explained this in a Twitter post stating that it’s impossible to rupture a normal tendon in vivo without pathology.

Interestingly, a study by Yasui et al. (2017) showed that only 4% with Achilles tendinopathy go on to rupture the tendon. So pain in tendinopathy might actually be protective of a rupture and this is a very good and re-assuring message for patients who are in tendon pain and afraid to rupture their tendons.

Alright, how many of those 7 were completely new to you?
As always, thanks a lot for reading!


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Whether you're working with high-level or amateur athletes you don't want to miss these risk factors which could expose them to higher risk of injury. This webinar will enable you to spot those risk factors to work on them during rehab!

Pathomechanics of lower limb muscle and tendon injuries