12.2 Tendinopathy Pathophysiology and Progressive Loading Protocols
Key Takeaways
Tendinopathy describes persistent tendon pain and impaired function related to loading. Symptoms, examination and capacity guide management alongside any imaging findings.
The Cook–Purdam continuum describes reactive, dysrepair and degenerative tissue presentations. These can overlap in the same tendon.
Progress from tolerable resistance through faster energy-storage tasks to sport-specific training when function and recovery support the next step.
In the Silbernagel Achilles trial, pain up to 5/10 during and after exercise was allowed if symptoms settled by the next morning and pain and stiffness did not worsen from week to week.
For irritable insertional Achilles tendinopathy, limit provocative dorsiflexion initially to reduce compression at the calcaneal attachment, then build range and load as tolerated.
Tendinopathy Pathophysiology and Progressive Loading Protocols
Tendons transmit force from muscle to bone. Some tendons, including the Achilles during running and hopping, also store and return elastic energy. Rehabilitation aims to improve the capacity to tolerate the loads that matter to the patient.
Tendon biology and clinical terminology
Type I collagen is the predominant collagen in tendon. Its organization helps the tendon transmit tensile force. Tenocytes maintain the extracellular matrix and respond to mechanical loading. This conversion of mechanical signals into cellular responses is mechanotransduction. Repeated loading can change the tissue, but an improvement in pain or performance does not require visible normalization on imaging.
The International Scientific Tendinopathy Symposium uses tendinopathy for persistent tendon pain and loss of function associated with mechanical load. The diagnosis does not specify a single histological process. Matrix changes and inflammatory signaling can coexist, and human tendon studies have found immune cells in some diseased samples. Assess the load-related symptoms, site and function, and consider other explanations when the pattern is atypical.
The Cook & Purdam Tendon Pathology Continuum
Cook and Purdam proposed a model to explain variation in load-related tendon pathology. Its stages describe tissue presentations that can overlap. The authors later described a reactive-on-degenerative presentation, in which a tendon with existing structural change becomes painful after a change in load.
| Model stage | Proposed tissue pattern | Rehabilitation implication |
|---|---|---|
| Reactive tendinopathy | Increased matrix water and tendon thickening after a load change, with relatively preserved collagen structure. | Reduce provocative load temporarily, then reintroduce tolerable loading. |
| Tendon dysrepair | Greater matrix disorganization and changes in cell activity. Vascular changes may be present. | Rebuild capacity through progressive exercise and monitor symptom and functional response. |
| Degenerative tendinopathy | Focal areas of more advanced matrix disruption. More organized tissue can coexist nearby. | Strengthen the muscle–tendon unit and progressively restore function, even if structural changes persist. |
The phrase “treat the donut” describes building capacity in the remaining load-bearing tissue when focal pathology is present. Ultrasound or MRI can show structural change, but the image alone cannot establish the source or intensity of pain, determine prognosis or specify a loading stage. Choose the starting load from the patient's symptoms and current function.
Progressive exercise is central to rehabilitation. Injection decisions depend on site, indication, expected benefit and risk and belong with the appropriate clinician. In one patellar tendinopathy trial, corticosteroid injection improved symptoms in the short term, while the improvement in the exercise groups was better maintained at follow-up.
The 4-Stage Progressive Tendon Loading Framework
Progress from tolerable muscle–tendon loading to the magnitude, rate and volume of loading required for sport. The four-stage patellar tendon programme studied by Breda and colleagues is one example. Stage choice and dosage depend on the tendon, symptoms and athletic demands.
- Isometric loading. A sustained contraction provides a way to load the tendon without joint movement. In a patellar tendon programme, participants began with five 45-second holds at about 70% of maximal voluntary force with the knee at about 60 degrees of flexion. That was a study protocol. Adjust the starting force, hold time and joint angle to the person. A small trial found short-term analgesia and reduced inhibition after isometrics, but other trials have not consistently shown superiority over dynamic loading.
- Isotonic resistance. Progress through a controlled range with both shortening and lengthening phases. Heavy slow resistance or a tolerable eccentric exercise can build strength and load capacity. For midportion Achilles tendinopathy, heavy slow resistance and eccentric training both have trial evidence. Increase load or range based on function and the response across sessions.
- Energy storage and release. Add faster tasks such as low hops, landings and direction changes once the athlete tolerates appropriate slower strength work. Increase speed, repetitions or complexity gradually. The Achilles and other spring-like tendons must tolerate rapid loading and return of elastic energy in these tasks.
- Sport-specific return. Build toward the speed, repetition and unpredictability of practice, then competition. Check strength, task quality, symptoms and recovery after exposure. For example, a jumping athlete may tolerate a few controlled landings before tolerating the repeated jumps and changes of direction in a full practice.
The Silbernagel Pain-Monitoring Model
In a randomized Achilles tendinopathy rehabilitation trial, Silbernagel and colleagues used a pain-monitoring model to guide continued activity. The trial allowed pain up to 5/10 during and immediately after exercise, with pain settling by the next morning. Pain and stiffness were also monitored for worsening from week to week. This is a way to adjust the exercise dose. A numerical pain score does not measure structural damage.
For example, a runner reports 4/10 during calf loading, with mild soreness that settles by the next morning and a stable week-to-week pattern. The current dose can be reassessed alongside heel-raise performance and running tolerance. If morning pain and stiffness remain worse or accumulate over successive sessions, reduce a loading variable such as range, resistance, repetitions or frequency and reassess. Sudden severe pain or abrupt loss of push-off raises a different concern and warrants evaluation for acute injury.
Site-Specific Athletic Tendinopathy Applications
| Condition | Clinical clues | Loading approach |
|---|---|---|
| Patellar tendinopathy | Focal patellar tendon pain, often at the inferior patellar pole, provoked by jumping or a decline squat. | Start with tolerable quadriceps loading. Adjust knee angle and resistance for irritability, then progress toward jump and landing demands. |
| Midportion Achilles tendinopathy | Gradual pain and tenderness several centimetres above the insertion, provoked by heel raises, running or hopping. | Use progressive calf loading. Eccentric heel drops or heavy slow heel raises are options. Progress range and resistance according to tolerance. |
| Insertional Achilles tendinopathy | Symptoms at the calcaneal attachment. Deep dorsiflexion can increase compression at the insertion. | Start with heel raises in a range that limits provocative dorsiflexion, such as from the floor. A heel lift can be considered. Progress functional range as tolerated. |
| Lateral elbow tendinopathy | Lateral epicondyle pain provoked by gripping or resisted wrist extension. | Progress resisted wrist-extensor exercise. Isometric, concentric and eccentric work can be selected for current tolerance and task demands. |
| Gluteal tendinopathy | Lateral hip pain with greater trochanter tenderness and symptoms during single-leg loading or resisted abduction. | Combine load-management education with progressive hip exercise. Reduce sustained compressive positions, such as provocative hip adduction, while rebuilding tolerance. |
In a patient with posterior heel pain, locating the symptoms at the attachment changes the starting exercise. The clinician may begin with a supported floor-level heel raise and track the response before increasing range. A heel-drop protocol designed for midportion symptoms is one option for that presentation and does not determine the initial range for an irritable insertion.
A basketball player with chronic load-related patellar tendon pain has focal disorganization on ultrasound. Their symptoms and function improve with a progressive exercise plan, although the scan still looks abnormal. How should the therapist interpret this?
Stop loading because pain relief requires normalization on ultrasound
Continue building load capacity based on symptoms and function. Organized tendon tissue can contribute to load bearing despite focal structural change
Prescribe plyometrics immediately to remove visible blood vessels
Use serial ultrasound alone to decide when the athlete can compete
A runner with irritable insertional Achilles tendinopathy has pain at the calcaneal attachment during heel drops below a step. What is the best initial loading modification?
Increase the depth of the heel drop to stretch the insertion under load
Use the same depth with the knee flexed to remove compression at the insertion
Start heel raises within a tolerable range that limits provocative dorsiflexion, such as from the floor
Replace calf strengthening with immediate maximal bounding
An athlete with midportion Achilles tendinopathy experiences 4/10 pain during calf strengthening. In the context of the Silbernagel pain-monitoring model, which response suggests a need to review and reduce the current load?
Morning walking pain has returned to its usual level
The athlete reports stable morning symptoms over the previous week
The session pain settles by the next morning and movement quality is stable
Pain and morning stiffness remain worse the next day and increase across successive sessions
An athlete with patellar tendinopathy tolerates a sustained quadriceps contraction better than a deep squat. Why might a midrange isometric be a reasonable starting exercise?
It provides an adjustable way to load the muscle–tendon unit without joint movement and may be better tolerated
It permanently removes neovascular vessels after one session
It reliably produces 45 minutes of analgesia in every athlete
It restores the athlete’s tolerance for repeated jumping without a graded loading progression
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