What Is Tendinopathy? — A Rope That Catches Up Slowly, a Load That Arrives First

"Your Tendon Has Inflammation"

A 45-year-old office worker restarts running after taking a break for several years. When they sharply increased their running distance in the first month, pain started right above the heel. It hurts more when running and walking up stairs, and less on days off. At the hospital, they are told, "Your tendon has inflammation, so get some rest." It seemed to improve after resting for a few weeks, but when they started running again, the same spot hurts anew.

Two questions remain for this person. Why did that exact spot hurt in the first place, and why did it hurt again after resting? This article starts with the structure of tendons, and looks in turn at the name changed from "inflammation", the spots where it commonly occurs, exercise as the center of treatment and its limits, injections and medication, and the moment a tendon tears.

Tendons Are the Cords Connecting Muscles to Bones

When you bend your elbow, the muscle at the front of your upper arm shortens and pulls on your forearm bone. A tendon is a tough cord that attaches the end of a muscle to a bone, transmitting the force generated by the muscle to the bone. In medical terms, it is called a tendon, and tendinopathy is also referred to as tendinopathy.

The main material making up tendons is collagen. Collagen is a tough fibrous protein that holds tissues together throughout the body, and in bones, it serves as the framework where minerals settle. In tendons, collagen fibers line up neatly along the direction of pull. The tissue arrangement of tendons is refined to do its job best (PMID 29345715), and thanks to that, tendons are strong yet flexible and elastic, but that very arrangement also makes them prone to injury (PMID 31361101).

Tendons change in response to the forces they receive. Load is the amount of work a tendon takes on, referring together to the intensity of the force applied at one time and the number of times that force is applied. Cells inside the tendon sense the load and, accordingly, change the arrangement, composition, and stiffness of the tendon (PMID 16000201).

There is a clue that tendon adaptation may lag behind muscle strength. In a small study where 8 people did resistance training for three months to strengthen knee extension, muscle strength had already risen by 29.6% at the 2-month mark, but tendon stiffness did not change until 2 months and rose noticeably only around the end of training (PMID 19996769). After stopping exercise, conversely, muscle strength stayed the same, but tendon stiffness returned to pre-training levels in 2 months. The authors viewed that tendon properties adapt later than muscle strength and revert faster when exercise is stopped (PMID 19996769). Because this was a single study looking at 8 people and the participants were not tendinopathy patients, this sequence and the number of months cannot be generalized as is.

If you compare a tendon to a rope, this rope gradually gets stiffer as the load it carries becomes heavier, but that speed is slow. If the load increases slowly, the rope keeps pace, but if the load increases suddenly, the load arrives before the rope can keep up.

A tendon is a living cord that changes on its own in response to the force it receives.

<!-- FIG: The Location of Tendons — One diagram showing how muscles, tendons, and bones are connected, like the calf muscle → Achilles tendon → heel bone, and a body diagram showing the four locations covered in this article (above the heel, below the kneecap, outside the elbow, and beside the hip) -->

From "Inflammation" to "Tendinopathy"

A 2006 review that looked at painful tendons under a microscope noted that signs of failed healing are visible, while inflammation is mostly absent (PMID 16849830). Inflammation is a reaction in which the body calls in immune cells, swells the area, and responds against stimuli such as injury, infection, or substances that have entered from outside the body. Tendon pain was once considered an inflammatory disease named "tendonitis," and it is now viewed by some as a series of connected changes (PMID 25818719). However, there are also counterarguments against dividing the stages of tendon pain primarily by structure (PMID 27127294). Therefore, instead of a name that puts inflammation first, tendinopathy is used as a term that broadly refers to conditions in and around the tendon caused by overuse (PMID 15634833, PMID 16849830).

Tendinopathy is a condition related to the heavy use of a tendon in which the tendon is painful and fails to perform its functions fully. In such tendons, collagen fibers are commonly disrupted, small blood vessels and sensory nerves increase, the balance of substances filling the space between fibers breaks down, immune cells and inflammatory substances increase, and cell death occurs frequently (PMID 33414454). However, this structural disruption is also common in painless tendons (PMID 31475937). Pain, decreased function, and a reduction in the capacity to handle exercise are the features of this disease (PMID 33414454).

The list includes immune cells and inflammatory substances. Although the core of tendinopathy is failed healing, the role that inflammation plays in the early stages before symptoms appear has been re-examined in recent years (PMID 28596062). A recent review on tendinopathy of the Achilles tendon also suggests that chronic inflammation commonly accompanies the structural breakdown process (PMID 40148342).

The change in name is connected to a change in treatment. A review on lateral hip tendinopathy noted that we should let go of the old belief of using rest and anti-inflammatory injections as the first treatments (PMID 39854929). Anti-inflammatory treatment can alter symptoms but may also promote tissue degeneration, whereas applying load to the tendon through exercise is considered to relieve symptoms and restore function in many patients (PMID 25818719).

Therefore, changes in the tendon seen on imaging and pain do not always go together. Even if tendon changes are visible in someone with front-of-knee pain, that pain may originate elsewhere (PMID 26390269). Thus, tendinopathy is diagnosed primarily through history and physical examination, and imaging is used only in special cases (PMID 31431267).

Tendinopathy is a state in which a tendon is painful and fails to perform its functions, typically underpinned by failed healing of its structure, and inflammation is being re-investigated as a part of that process.

Four Common Sites

Roughly 6% of the general population experience trouble in the Achilles tendon during their lifetime, and among elite long-distance runners, that proportion reaches as high as half (PMID 40148342). The most common sites for tendinopathy caused by overuse are the shoulder, the inside and outside of the elbow, below the kneecap, the side of the hip, and the Achilles tendon (PMID 33414454). Shoulder tendons are covered in "What Is Shoulder Pain? — A Ball on a Shallow Socket, a Gripping Hand and a Wrapped Pouch", and here we look at the remaining four sites.

The Achilles tendon is a thick tendon connecting the lower end of the calf muscle to the heel bone, transmitting the force to stand on tiptoe and push off the ground. Achilles tendinopathy is typically characterized by localized pain at that site, which worsens during activities that place a load on the tendon (PMID 34099611).

The patellar tendon is the tendon running from the lower end of the kneecap to the shinbone, transmitting the force with which the front thigh muscle straightens the knee. Tendinopathy of this tendon concentrates pain at the lower end of the kneecap, and hurts more the more work is placed on the knee-extending muscles—especially in activities where the tendon stores and releases force, such as jumping (PMID 26390269).

Tennis elbow (lateral elbow tendinopathy) is tendinopathy occurring in the tendons of the wrist extension muscles, which attach to the prominent bone on the outside of the elbow. Although the name includes tennis, the tennis elbow trials cited in this article recruited patients who visited primary care clinics and hospital outpatients rather than athletes (PMID 23385272, PMID 39806585).

Gluteal tendinopathy is tendinopathy occurring in the tendons where the buttock muscles on the side of the pelvis attach to the prominent upper outer part of the thigh bone. It is a common condition that has a major impact on daily life (PMID 39854929).

Though the sites differ, the beginnings are similar. A load greater than the tendon usually handles is the main cause of symptoms appearing (PMID 31431267), and patients often report that the pain began after a change in activity (PMID 31361101). To picture it with a rope, it is the spot where the load increased faster than the rope could keep up. However, this is just one explanation, and there is not yet a consensus on how tendinopathy develops (PMID 31431267). Besides load, other factors are involved. Achilles tendinopathy is also associated with side effects of certain medications, age, and various underlying medical conditions (PMID 40148342).

Tendinopathy commonly begins when a load greater than the tendon usually handles is placed upon it.

Rather Than Just Resting, Increasing Gradually

For tendinopathy in the middle section of the Achilles tendon, which sits above the attachment point on the heel bone, any active treatment—whether exercise or injections—appeared better at the 3-month mark than simply waiting it out. This is the result of an analysis bringing together 29 trials comparing treatments (PMID 32522732). A randomized controlled trial is a study where participants are divided randomly, like a draw, so that only one group receives a certain treatment while the results are compared against the other group. Among the randomized controlled trials included in this analysis, not a single one was at a low risk of bias, there appeared to be no clinically meaningful differences among the active treatments at either 3 months or 12 months, and the certainty of the evidence ranged from very low to low. The authors wrote that because exercise can be easy to prescribe, low in cost, and carries few harms, starting treatment with calf muscle exercises can be considered (PMID 32522732).

Resting also has its place. Relative rest, which involves modifying activities and using the tendon less, is one pillar of treatment, and starting rehabilitation exercises early is also seen to help (PMID 31361101). However, the evidence supports regulating loads and slowly building them back up rather than just resting completely, and other treatments are used mainly as supports to ease pain (PMID 31431267). In gluteal tendinopathy, exercise and education showed a medium-sized effect on short-term pain and function (with a moderate strength of evidence), while the medium- and long-term effects were small, and the authors wrote that exercise and education can be cautiously recommended as core components (PMID 40223303). Multidisciplinary Dutch expert guidelines recommend starting with exercise therapy after diagnosing patellar tendinopathy, while rating the certainty of that evidence as low (PMID 39045713).

Eccentric exercise has long held the representative spot in Achilles and patellar tendinopathy, yet in some cases as many as 45% of patients do not respond to this exercise (PMID 23494258). Eccentric exercise is a movement where the muscle lengthens while generating force, like resisting and lengthening when lowering a weight slowly. However, one randomized trial in Achilles tendinopathy showed that exercises lifting and lowering heavy weights slowly produced results just as good as eccentric exercise (PMID 26018970), and a recent analysis also concluded that eccentric exercise can be an option for load exercise as a first treatment, but is not a superior golden standard compared to other exercises (PMID 42021217).

The suitability of exercise differs by site. In a small Norwegian trial examining feasibility by gathering tennis elbow patients, only 6 of 19 patients assigned to slow heavy-resistance training followed the exercise as planned, with the main reason being worsening pain. The authors wrote that this exercise appeared unsuitable for tennis elbow patients, and in that study as well, symptoms improved in all three groups (PMID 39806585). The evidence addressing the effects of exercise and manual therapy in tennis elbow is limited or conflicting apart from a few exceptions, yet the authors still considered these results to support the belief that strengthening exercises reduce symptoms (PMID 23709519). While pain is commonly used as a guideline for when and how much to increase exercise, neither the approach of increasing it strictly below the pain threshold nor the approach of allowing a certain degree of pain is supported by strong evidence (PMID 33444210).

Recovery is measured in months. Rehabilitation for patellar tendinopathy is slow and sometimes frustrating, and expecting too short a recovery period is cited as a common pitfall (PMID 26390269). Treatments are lengthy and poor responses are frequent (PMID 15634833).

The rope analogy has limits. Evidence is building that a structural repair of the tendon's weave is not strictly necessary for improvement through rehabilitation (PMID 31475937). In the Achilles tendon, imaging improvements and symptom improvements mostly did not go hand in hand, and what consistently went hand in hand with symptom improvement in both the Achilles and patellar tendons was improvements in muscle strength and endurance (PMID 23494258). The path to getting better is not just one of the rope growing thicker.

The core of treatment is exercise that gradually increases the load to amounts the tendon can tolerate, rather than removing the load and waiting, the size of that benefit has limits, and recovery is measured in months.

Short-Term Relief, Long-Term Cost

There is an Australian randomized controlled trial that divided 165 people whose tennis elbow lasted longer than 6 weeks into four groups (PMID 23385272). A steroid injection is an injection that uses a needle to place steroid-family drugs, which calm inflammation, close to the painful spot. In tendinopathy, they are commonly placed around the painful tendon (PMID 20970844). A year later, the proportion of people who had completely recovered or improved significantly was 83% in the group that received the steroid injection and 96% in the group that received the fake injection, while the proportion of people who recovered once and then worsened again was 54% in the steroid group and 12% in the fake injection group (PMID 23385272). In the same trial, whether or not physical therapy combining multiple methods was added made no difference to the results 1 year later, and at the 4-week mark, the group that combined physical therapy with the fake injection showed significantly more improvement than the group that did not (PMID 23385272).

The same pattern repeats across multiple trials. In an analysis pooling 41 randomized controlled trials covering injection treatments for tendinopathy, steroid injections reduced pain more than other treatments in the short term, but that effect reversed half a year and a year later (PMID 20970844). In tennis elbow, the same order appeared even when compared with a group that received no treatment at all. The authors added that because the effects differ by tendon site, the response to injections should not be generalized (PMID 20970844).

<!-- FIG: Short-Term Relief, Long-Term Cost — Side-by-side comparison of pain changes in tennis elbow between the steroid injection group and the untreated group at three time points: the first few weeks, half a year, and one year. The main point is that the injection group is ahead at first, but the order reverses later (without numerical values) -->

In a randomized trial dividing 39 men with patellar tendinopathy, steroid injections were good at 12 weeks and bad half a year later, whereas exercise consisting of slowly lifting and lowering heavy weights was good at both time points (PMID 19793213). In lateral hip tendinopathy, steroid injections showed a small effect on short-term pain (PMID 40223303).

Injections tearing a tendon are rare. Among 991 people who received steroid injections in trials reporting side effects, the severe side effect of a ruptured tendon occurred in 1 person (0.1%) (PMID 20970844). Even so, it is considered that caution is required due to the risk of rupture when injecting steroids into or near major tendons that bear substantial weight (PMID 31361101).

Nonsteroidal anti-inflammatory drugs are a group of analgesic and anti-inflammatory drugs widely used to reduce pain, fever, and inflammation. Regarding the role of anti-inflammatory painkillers, perspectives are divided. One review reports that short-term use reduces pain and increases the range of motion, helping to complete rehabilitation exercise (PMID 31361101), while another review views that although symptoms can be altered, it may also encourage tissue degeneration (PMID 25818719). Platelet-rich plasma injections showed better results after several months in an analysis comparing various diseases of the tendon and its surroundings grouped together against steroid injections, but long-lasting effects have not yet been confirmed (PMID 40200209), and in Achilles tendinopathy, they were no better than fake injections (PMID 20970844).

Steroid injections reduce pain in tennis elbow during the first few weeks, but the results half a year and a year later were actually worse, and the effectiveness of injections varies by tendon site.

Medication and Tendons

Certain antibiotics are associated with an increased risk of tendon rupture. Fluoroquinolones are a group of antibiotics widely used for various infections. They are well absorbed, spread well throughout the body, and are widely used against many bacteria (PMID 22035890), and some of the most prescribed antibiotics in the world belong to this class (PMID 40005998). Because severe side effects such as myopathy, hearing loss, tendinopathy, and tendon rupture can occur, health agencies around the world have advised reducing their prescription (PMID 40005998). Reports of tendon trouble were especially frequent in older adults and those with diabetes or renal failure (PMID 22035890).

In an observational study comparing people with and without tendon rupture using British primary care records, current use of this class was associated with about a 3-fold (3.14-fold) higher risk of Achilles tendon rupture, and that risk lasted for 60 days (PMID 30465300). The risk increased with greater use and was highest when oral steroids were used concurrently. In terms of absolute magnitude, using this class resulted in about 2.1 more Achilles tendon ruptures per 10,000 people, and among those aged 60 and older taking oral steroids concurrently, there were 19.6 more ruptures of any tendon and 6.6 more Achilles tendon ruptures per 10,000 people. Use of other antibiotic classes showed no such association (PMID 30465300).

A systematic review pooling observational studies points in the same direction. The risk was particularly high in the first month after taking the drug, higher when oral steroids were used concurrently, and the complications themselves appeared rare (PMID 23888427). Drug-induced tendinopathy is a rare but repeatedly confirmed complication, and the sites troubled by this class and long-term steroid use are mainly the large tendons of the leg, especially the Achilles tendon (PMID 28553748).

These numbers tell us two things together. The risk is real, but for most people it amounts to 2 to 3 more cases per 10,000 people, and it grows to nearly 20 per 10,000 people in those aged 60 and older who use oral steroids concurrently. Management of fluoroquinolone-associated tendinopathy includes immediate discontinuation of the drug, rest, anti-inflammatory pain relievers, physical therapy, and eccentric exercise, and surgery may be necessary if the tendon ruptures (PMID 22035890). However, the decision to stop the drug or switch to another medication is made by the prescribing physician by weighing the person's infection and risks together, as there are infections for which this class is strictly necessary.

Fluoroquinolones are associated with an increased risk of tendon rupture, but the absolute magnitude is usually 2 to 3 per 10,000 people, and is largest at nearly 20 per 10,000 people in those aged 60 and older taking oral steroids concurrently.

When the Achilles Tendon Tears

The Achilles tendon is both the strongest and largest tendon in the body and the most commonly ruptured one (PMID 28257676). This is thought to be because the Achilles tendon has a sparse blood supply and unevenly distributed loads (PMID 37946221). An Achilles tendon rupture is an injury where the Achilles tendon suddenly tears, preventing the force of the calf muscle from being transmitted to the heel. Candidate risk factors included medications like steroids and fluoroquinolones, Achilles tendinopathy, diabetes, and regular participation in sports, but the certainty of evidence for all of them was low or very low (PMID 35670156). Pre-existing tendon degeneration is also pointed out as a risk factor for sudden rupture (PMID 16849830).

When an Achilles tendon tears, it commonly feels like being kicked from behind just above the heel or makes a popping sound, after which one cannot stand on the toes of the injured foot. Because this sudden change must be handled differently from long-standing tendon pain, confirming it through a physical examination comes first. Missing the diagnosis or delaying treatment is considered to worsen outcomes and reduce available treatment options (PMID 37946221). Combining an appropriate history of the injury, feeling for a hollow gap at the tear site with the hand, and checking whether the foot moves when the calf is squeezed while lying facedown makes it rare to miss a rupture (PMID 39228352). Imaging is used only when the physical examination is ambiguous, and in that case, ultrasound comes first (PMID 28257676, PMID 39228352).

In a randomized controlled trial of 554 patients who had just torn their tendon across four hospitals, divided into non-surgical, open surgery, and minimally invasive surgery groups, symptom and function scores at 12 months were similar among the three groups (PMID 35417636). Re-ruptures were more frequent in the non-surgical group at 6.2% compared to the surgical group (0.6%), while nerve injuries were more frequent in the surgical group, particularly the minimally invasive surgery group (PMID 35417636). A re-rupture is when a treated tendon tears again.

Even in an analysis pooling 29 trials and observational studies, surgery reduced re-ruptures, but the difference was a small 1.6 percentage points, while other complications—centered on infections—increased by 3.3 percentage points (PMID 30617123). Early functional rehabilitation is rehabilitation that does not keep a torn tendon immobilized for long, having the patient bear weight and move the ankle from an early stage. In studies using early functional rehabilitation, the difference in re-ruptures was not distinct (PMID 30617123), and in a randomized trial of 144 patients where both groups received early functional rehabilitation, there were no clinically important differences in re-rupture and muscle strength while complications were more frequent in the surgical group, leading the authors to view these results as supporting early functional rehabilitation and non-surgical treatment (PMID 21037028).

Recent analyses place weight on slightly different sides. A recent analysis pooling only randomized trials found that surgery substantially reduced re-ruptures, open surgery increased complications, functional assessments showed no differences, and minimally invasive surgery led to a faster return to work without a clear difference in complications (PMID 41243574). One review noted that combining minimally invasive surgery with early functional rehabilitation appears to yield the best outcomes (PMID 36143872), while a Dutch review recommended non-surgical treatment unless there is a strong reason otherwise, noting that surgery can be considered when the risk of re-rupture is high, such as in athletes or people with physically demanding jobs (PMID 39228352). The authors of the aforementioned analysis of 29 studies concluded that the final decision should be made together based on each patient's individual circumstances (PMID 30617123).

An Achilles tendon rupture sees reduced re-ruptures and increased other complications with surgery, with almost no difference in function a year later, so which option to choose is decided alongside the person's circumstances.

The Runner Who Started Again

Let us return to that first person. After taking a few years off, they sharply increased their distance in the first month, and the area above their heel hurt more when running. A load greater than what a tendon usually handles is a common site where tendinopathy begins (PMID 31431267), and focal pain that hurts more when a load is placed on the tendon is the classic presentation of Achilles tendinopathy (PMID 34099611).

Why it hurt again after resting cannot be determined solely from this person's story. What the evidence tells us is the direction. Relative rest to adjust activity is one pillar of treatment (PMID 31361101), but the evidence supports adjusting the load and slowly building it back up rather than just resting completely (PMID 31431267). Among the words saying "it is inflammation, so rest," the current evidence points away from the side of resting entirely. In mid-portion Achilles tendinopathy, active treatment looked better at the 3-month mark than a wait-and-see approach (PMID 32522732). However, the certainty of that evidence is low, there were no clear differences among types of exercise (PMID 32522732, PMID 42021217), and pain is commonly used as a guide for increasing exercise, but neither the method of increasing it just short of causing pain nor the method of allowing some degree of pain is backed by strong evidence (PMID 33444210). While there is a review stating that Achilles tendinopathy mostly shows a favorable course improving with activity modification and progressive loading rehabilitation (PMID 34099611), there is also a review stating that treatment is long, difficult, and frequently fails (PMID 40148342). Either way, that timeframe is on the scale of months (PMID 16849830).

If you think of injections, the evidence showing short-term gains and long-term harms comes mainly from tennis elbow and patellar tendinopathy, and the response to injections differs by location (PMID 20970844). When injecting steroids near a tendon that bears a heavy load like this person's Achilles tendon, it is considered necessary to be cautious due to the risk of rupture (PMID 31361101). If this person is prescribed fluoroquinolone-class antibiotics for another illness, that risk is real but rare, and its magnitude varies depending on age and oral steroids (PMID 30465300). And if one day while running it feels as though the area above the heel was kicked or you hear a snap and it becomes difficult to push off with the toes of the injured foot, that is a matter that must be handled differently from long-dragging pain, something to be checked by physical examination, and it is considered that delayed diagnosis and treatment lead to poorer outcomes (PMID 37946221). How to tailor this sequence to this person is something to be decided in the clinic.

Where to Look Next

We do not yet fully understand how the structure, pain, and function of tendons interlock with one another (PMID 27127294), and it remains unclear which treatments among exercise, injections, and surgery work, or by how much (PMID 33414454).

The principles by which exercise becomes a treatment and the work of recovering function are continued in "Rehabilitation — Starting to Plan a Livable Home as the Fire Is Brought Under Control", and the question of how much exercise one should do is continued in "How Much Is Enough — An Introduction to Dose-Response in Rehabilitation".

The story that bone is also a living tissue that becomes as sturdy as it is used begins in "How Is Bone Alive? — A Site That Builds as It Tears Down, a Warehouse the Body Draws On". The discrepancy between imaging findings and pain is encountered again in other contexts in "What Is Knee Osteoarthritis? — The Door Frame That Changes With the Hinge" and "What Is Low Back Pain? — Wrinkles in the Spine, Pain Without a Name". Shoulder tendons are covered by "What Is Shoulder Pain? — A Ball on a Shallow Socket, a Catching Hand and a Wrapped Pouch", and pain itself that continues for more than several months is covered by "What Is Chronic Pain? — The Microphone and Amplifier, a Sound Ringing for More Than Three Months".

Source Papers

• "Tendon - function-related structure, simple healing process and mysterious ageing." (2018) — PMID 29345715 — Tendon structure is tuned for optimal function, and although healing may look simple, complete recovery failing is common.
• "Management of Chronic Tendon Injuries." (2019) — PMID 31361101 — Tendons possess strength, flexibility, and elasticity together, but that makes them easy to injure; diseased tendons feature a disorganized degenerative recovery rather than inflammation, making tendinopathy preferred over tendinitis. It frequently starts after activity changes, anti-inflammatory painkillers and steroids reduce pain briefly to help rehabilitation, and steroid injections in or near large weight-bearing tendons require caution due to rupture risk.
• "Time course of changes in muscle and tendon properties during strength training and detraining." (2010) — PMID 19996769 — In 8 people completing 3 months of knee extension isometric training, strength and neural drive already rose at 2 months (29.6% and 7.3%), muscle cross-sectional area and tendon stiffness did not change until month 2 and then rose significantly by the end of training, and during detraining, strength was maintained while tendon stiffness returned to pre-training levels at 2 months — tendon and muscle structural adaptations are slower than muscle function, and detraining drops them faster (small single study).
• "iTRAQ-based proteomics reveals potential markers and treatment pathways for acute Achilles tendon rupture." (2023) — PMID 37946221 — (Background description only cited) A background sentence noting that limited blood supply and irregular mechanical loads make the Achilles tendon the most commonly ruptured tendon, and missed diagnoses or delayed treatment lead to poor outcomes and limited treatment choices. The study itself is proteomic analysis.
• "Mechanobiology of tendon." (2006) — PMID 16000201 — Tendons change their structure, composition, and mechanical properties in response to forces (mechanical adaptation), and cells mediate this, but the mechanism by which cells turn forces into signals is poorly understood.
• "Biology of tendon injury: healing, modeling and remodeling." (2006) — PMID 16849830 — Tendinopathy is an umbrella term for diseases in and around tendons caused by overuse, tendinosis and tendinitis only follow tissue biopsy, recovery is disorganized and inflammation is usually not seen, pre-existing degeneration is a risk factor for acute rupture, disability lasts for months despite proper treatment, and tennis elbow tendinopathy reaches up to 40%.
• "Treating tendinopathy: perspective on anti-inflammatory intervention and therapeutic exercise." (2015) — PMID 25818719 — Once viewed as an inflammatory disease called tendinitis, it is now seen as a continuum; anti-inflammatory treatments alter symptoms but may encourage degeneration, and eccentric contraction-focused load exercise promotes symptom resolution and functional recovery in many patients.
• "Tendon injury and tendinopathy: healing and repair." (2005) — PMID 15634833 — Tendinopathy is the best umbrella term for overuse tendon disease, treatment is long and responses are often poor, and pre-existing degeneration is a risk factor for acute rupture.
• "Tendinopathy." (2021) — PMID 33414454 — Pain, functional decline, and reduced exercise tolerance; the most common sites are the rotator cuff, inner/outer elbow, patellar tendon, gluteal tendons, and Achilles; collagen disorganization, increased microvessels and sensory nerves, matrix homeostasis breakdown, increased immune cells and inflammatory mediators, and increased apoptosis; treatment efficacy remains unclear.
• "Inflammation in tendinopathy." (2017) — PMID 28596062 — The core lesion of tendinopathy is a failed healing response, and the role of inflammation in early stages before it becomes clinically apparent has recently been re-highlighted.
• "Achilles tendinopathy." (2025) — PMID 40148342 — About 6% of the general population and up to 50% of elite endurance runners experience Achilles pathology over their lifetime; load-related local pain and functional impairment; repetitive overload is a common trigger, but it is also linked to drug side effects, aging, and comorbidities; tissue disorganization is frequently accompanied by persistent inflammation; treatment is long and has a high failure rate.
• "How do tendons adapt? Going beyond tissue responses to understand positive adaptation and pathology development: A narrative review." (2019) — PMID 31475937 — Load prompts adaptation but is also a major driver of pathology and pain; asymptomatic pathology is common; growing evidence shows that tendon remodeling and repair are not strictly necessary for good outcomes after rehabilitation.
• "Patellar Tendinopathy: Clinical Diagnosis, Load Management, and Advice for Challenging Case Presentations." (2015) — PMID 26390269 — Local pain at the lower end of the kneecap and pain increasing with loads on the knee-extending muscles (especially activities storing and releasing energy); diagnosis is clinical because of asymptomatic tendon pathology; management builds load tolerance progressively; rehabilitation can be slow and frustrating, with unrealistic duration expectations and reliance on passive treatments being common pitfalls.
• "Current trends in tendinopathy management." (2019) — PMID 31431267 — Overload exceeding normal capacity is the main cause, with a tendency toward chronic progression and long recovery; diagnosis is mostly clinical and imaging is for special cases; evidence supports progressively advancing loading programs over complete rest, with other treatments mainly serving as pain relief adjuncts.
• "Achilles Tendinopathy: Evaluation, Rehabilitation, and Prevention." (2021) — PMID 34099611 — Local pain worsened by loading activities, mostly diagnosed clinically, with a good prognosis mostly improving with activity modification and progressive load rehabilitation, procedures for refractory cases, and rare surgery.
• "Gluteal tendinopathy masterclass: Refuting the myths and engaging with the evidence." (2025) — PMID 39854929 — A common and impactful condition, letting go of the tradition of prioritizing rest and steroid injections to self-manage through education, load management, progressive exercise, and overall health optimization.
• "The efficacy of gluteal tendinopathy treatments: A systematic review." (2025) — PMID 40223303 — Exercise plus education has a moderate effect on short-term pain and function (moderate certainty) and a small effect in the medium- to long-term; steroid injections have a small effect on short-term pain; exercise plus education is cautiously recommended as the core.
• "Which treatment is most effective for patients with Achilles tendinopathy? A living systematic review with network meta-analysis of 29 randomised controlled trials." (2021) — PMID 32522732 — 29 trials, none at low risk of bias; all active treatments look better than waiting at 3 months (very low to low certainty); no clinical difference among active treatments at 3 and 12 months; exercise is easy to prescribe, low-cost, and low-harm, so starting with calf exercises is worth considering.
• "Dutch multidisciplinary guideline on anterior knee pain: Patellofemoral pain and patellar tendinopathy." (2025) — PMID 39045713 — Start with exercise therapy after clinical diagnosis, add other conservative treatments only if there is no response at 12 weeks; imaging has limited added value; exercise is advocated as a first-line strategy despite low certainty of evidence (patellar tendinopathy).
• "Achilles and patellar tendinopathy loading programmes : a systematic review comparing clinical outcomes and identifying potential mechanisms for effectiveness." (2013) — PMID 23494258 — Eccentric exercise was the dominant conservative treatment, but evidence of its superiority is limited (Achilles) and conflicting (patellar); little evidence supports isolating eccentric exercise alone; improved neuromuscular performance is the only factor consistently linked to clinical improvement in both tendons; imaging improvements and clinical outcomes are mostly unrelated in the Achilles; quality studies are lacking.
• "Heavy Slow Resistance Versus Eccentric Training as Treatment for Achilles Tendinopathy: A Randomized Controlled Trial." (2015) — PMID 26018970 — 58 people with midportion Achilles tendinopathy lasting over 3 months; both eccentric exercise and heavy slow resistance training improved outcomes at 12 weeks and maintained them up to 52 weeks, with no difference between groups, though satisfaction at 12 weeks tended to favor the resistance training group.
• "The efficacy of eccentric exercise in the treatment of Achilles tendinopathy: a systematic review and meta-analysis." (2026) — PMID 42021217 — 21 trials with 994 participants; pain reduction is greater than with physical therapy alone but similar to other exercises; functional outcomes have very high heterogeneity preventing a conclusion; load intensity may be the core driver; it can be a first-line treatment choice, but it is not a superior gold standard over other exercises.
• "Heavy slow resistance training, radial extracorporeal shock wave therapy or advice for patients with tennis elbow in the Norwegian secondary care: a randomised controlled feasibility trial." (2024) — PMID 39806585 — 60 participants in a single-center feasibility trial; 6 out of 19 participants (32%) adhered to heavy slow resistance training, mostly due to worsening pain, suggesting it is ill-suited for tennis elbow; all groups showed improved results.
• "Does effectiveness of exercise therapy and mobilisation techniques offer guidance for the treatment of lateral and medial epicondylitis? A systematic review." (2013) — PMID 23709519 — 12 trials (all on lateral elbow); some moderate-quality evidence such as short-term effects of stretching plus strengthening; the rest is limited, conflicting, or absent; not definitive, but supports the belief that strengthening exercise reduces symptoms.
• "Load progression criteria in exercise programmes in lower limb tendinopathy: a systematic review." (2020) — PMID 33444210 — 30 studies; pain-based progression criteria are mainly used but not supported by strong evidence.
• "Effect of corticosteroid injection, physiotherapy, or both on clinical outcomes in patients with unilateral lateral epicondylalgia: a randomized controlled trial." (2013) — PMID 23385272 — 165 participants with lateral elbow pain lasting over 6 weeks in a 2×2 trial; 1-year complete recovery or much improvement was 83% for steroids versus 96% for placebo; 1-year recurrence was 54% versus 12%; physical therapy status made no difference at 1 year (there was a benefit at 4 weeks from fake injection plus physical therapy); steroids worsen 1-year outcomes.
• "Efficacy and safety of corticosteroid injections and other injections for management of tendinopathy: a systematic review of randomised controlled trials." (2010) — PMID 20970844 — 41 trials with 2,672 participants; short-term pain reduction from steroid injections reverses in the medium- to long-term; for the outer elbow, there is a large short-term effect compared to no treatment, but no treatment is better at 26 and 52 weeks; out of 991 participants, serious side effects (tendon rupture) occurred in 1 (0.1%); PRP and others are no better than placebo in the Achilles; effects vary by site so generalization is forbidden.
• "Corticosteroid injections, eccentric decline squat training and heavy slow resistance training in patellar tendinopathy." (2009) — PMID 19793213 — Randomized trial of 39 men; steroid injections are good short-term and bad long-term, while heavy slow resistance training is good both short- and long-term.
• "Platelet-rich plasma and corticosteroid injection for tendinopathy: a systematic review and meta-analysis." (2025) — PMID 40200209 — 27 trials with 1,779 participants; the medium-term efficacy of PRP is superior to steroids, but long-term efficacy needs further verification.
• "Fluoroquinolone-associated tendinopathy." (2011) — PMID 22035890 — Widely used due to absorption, tissue penetration, and broad antibacterial spectrum; tendinopathy and rupture reported in the elderly, diabetics, and renal failure patients; management includes immediate drug cessation, rest, anti-inflammatory painkillers, physical therapy, and eccentric exercise; ruptures may require surgery.
• "Fluoroquinolone-Mediated Tendinopathy and Tendon Rupture." (2025) — PMID 40005998 — One of the world's most prescribed antibiotic classes; health agencies in various countries recommend prescription restrictions due to severe side effects such as myopathy, hearing loss, tendinopathy, and rupture; exact molecular mechanisms remain unknown.
• "Relative and Absolute Risk of Tendon Rupture with Fluoroquinolone and Concomitant Fluoroquinolone/Corticosteroid Therapy: Population-Based Nested Case-Control Study." (2019) — PMID 30465300 — Nested case-control study using UK primary care data; current exposure yields an Achilles rupture aIRR of 3.14 lasting for 60 days, increasing with cumulative exposure and concurrent oral steroid use; absolute risk difference is 2.1 per 10,000 for Achilles (2.9 for all tendons); in those aged 60+ taking oral steroids, it reaches 19.6 per 10,000 for all tendons and 6.6 for Achilles.
• "Tendon Injury and Fluoroquinolone Use: A Systematic Review." (2013) — PMID 23888427 — 16 observational studies; increased risk of Achilles rupture in the first month after exposure (odds ratio 1.1 to 7.1); increased risk when combined with oral steroids; complications appear rare; limitations include reliance on self-reporting.
• "Mini-Review: Toxic Tendinopathy." (2017) — PMID 28553748 — Drug-induced tendinopathy is a rare but reproducible complication; fluoroquinolones, long-term glucocorticoids, and statins are common in large weight-bearing tendons of the leg, especially the Achilles; mechanisms are incompletely understood.
• "Acute Achilles Tendon Rupture: Clinical Evaluation, Conservative Management, and Early Active Rehabilitation." (2017) — PMID 28257676 — The Achilles is the strongest, largest, and most commonly ruptured tendon; physical exam sensitivity and specificity are high; imaging is used only when the physical exam is ambiguous; early weight-bearing and controlled early movement improve outcomes and satisfaction in both surgical and nonsurgical management.
• "Risk factors for Achilles tendon rupture: an updated systematic review." (2023) — PMID 35670156 — 19 papers; risk factors including steroids, quinolones, bisphosphonates, Achilles tendinopathy, diabetes, and regular exercise participation all have low to very low certainty; multi-factorial injury.
• "[Acute Achilles tendon rupture; intend to treat conservatively]." (2024) — PMID 39228352 — Functional outcomes are similar between conservative and surgical treatments, so conservative treatment is recommended unless a strong reason exists; medical history, palpable gap, and Thompson test sensitivity are very high; ultrasound first if suspected; shared decision-making; surgery considered if re-rupture risk is high, such as in athletes or physical laborers.
• "Nonoperative or Surgical Treatment of Acute Achilles' Tendon Rupture." (2022) — PMID 35417636 — Randomized trial of 554 patients across 4 Norwegian centers; 12-month symptom score changes were similar across three groups; re-rupture was 6.2% for nonoperative versus 0.6% for each surgical group; nerve damage was 5.2% for small incision, 2.8% for open incision, and 0.6% for nonoperative; surgery was not associated with better outcomes at 12 months.
• "Operative treatment versus nonoperative treatment of Achilles tendon ruptures: systematic review and meta-analysis." (2019) — PMID 30617123 — 29 studies (10 trials, 19 observational); re-rupture was 2.3% for surgery versus 3.9% for nonoperative (risk difference 1.6%); other complications were 4.9% versus 1.6% (difference 3.3%, mostly infection); early movement functional rehabilitation studies show no significant difference in re-rupture; final decisions depend on patient factors and shared decision-making.
• "Operative versus nonoperative treatment of acute Achilles tendon ruptures: a multicenter randomized trial using accelerated functional rehabilitation." (2010) — PMID 21037028 — 144 participants, both groups underwent early functional rehabilitation; re-rupture occurred in 2 surgical patients and 3 nonoperative patients; no clinical differences in strength or range of motion; complications totaled 13 in the surgical group and 6 in the nonoperative group (mostly soft tissue).
• "Operative versus nonoperative management of acute Achilles tendon rupture: a systematic review and meta-analysis of clinical outcomes from randomized controlled trials." (2025) — PMID 41243574 — 14 trials with 1,628 participants; both small incision and open surgeries reduced re-ruptures, open surgery increased complications, no difference in functional evaluations, and small incision surgery had faster recovery.
• "The Acute Achilles Tendon Rupture: An Evidence-Based Approach from the Diagnosis to the Treatment." (2022) — PMID 36143872 — Synthesis of 13 systematic reviews; strong consensus on the re-rupture risk of nonoperative treatment and complication risk of surgery; small incision surgery plus early functional rehabilitation appears to yield the best results.
• "Revisiting the continuum model of tendon pathology: what is its merit in clinical practice and research?" (2016) — PMID 27127294 — The structural stage-based continuum model is challenged because it classifies pain pathology primarily by structure; the interplay between structure, pain, and function is not yet fully understood.