Tendinopathy: State of the Evidence – Achilles and ­Patellar Tendinopathies

Speaker: Karin Grävare Silbernagel, Professor and Associate Chair, Department of Physical Therapy. Director, Center for Human Research Coordination, University of Delaware, USA
Congress: Sport & Exercise Medicine Switzerland and Swiss Sport Physiotherapy Association joint conference: “Structure & Function”, Lausanne, October 30^th and 31^st 2025

Scan to access presentation on Sportfisio YouTube channel

Introduction

Tendinopathy represents a significant clinical challenge in musculoskeletal medicine, affecting both athletic and sedentary populations. Recent research has transformed our understanding of this condition from a simple inflammatory process to a complex, multifactorial pathology requiring individualized treatment approaches. This article synthesizes current evidence presented by Professor Karin Grävare Silbernagel regarding tendinopathy assessment, management, and emerging therapeutic strategies.

The Paradigm Shift: From Tendinitis to ­Tendinopathy

The evolution of tendinopathy management reflects fundamental changes in pathophysiological understanding. Historically conceptualized as “tendinitis”—an acute inflammatory process—treatment centered on rest, cryotherapy, and NSAIDs with strict activity avoidance. Research in the late 1990s challenged this inflammatory model, demonstrating that chronic tendon pathology represents a degenerative or failed healing response rather than acute inflammation. This recognition precipitated a paradigm shift with profound therapeutic implications: mechanical loading is not only safe but essential for tendon healing, exercise despite pain is therapeutic, and some structural normalization can occur with appropriate loading protocols (Table 1). Exercise-based interventions now have the highest level of evidence for tendinopathy management, though clinical challenges persist with only 60-80% success rates, 6-12 month recovery timelines, and high recurrence rates.

Reconceptualizing Tendinopathy as a Biological Disease

Contemporary evidence supports viewing tendinopathy beyond simple overuse athletic injury. Increasing incidence in older adults and adolescents, strong associations with metabolic disorders, and quality of life impairment comparable to knee osteoarthritis suggest a broader disease model. This reconceptualization may facilitate more comprehensive treatment strategies.

The Five Domains of Tendon Health

Factor analysis has identified five distinct, uncorrelated domains:
1. Structure: Tendon morphology and architecture
2. Function: Physical performance and biomechanical capacity
3. Symptoms: Pain and other subjective complaints
4. Personal factors: Demographics, activity level, comorbidities
5. Psychological factors: Kinesiophobia, catastrophizing, quality of life

This lack of correlation is clinically critical—patients may exhibit high symptom burden with preserved function, significant structural abnormalities with minimal symptoms, or functional deficits without proportional structural changes. This multi-domain model supports comprehensive assessment rather than relying on single outcome measures and explains why imaging findings or pain scores alone poorly predict functional recovery.

Patient Subgroups: Toward Personalized Medicine

Cluster analysis has identified four distinct patient phenotypes with unique treatment responses. The Activity Dominant group (younger, 68% runners, minimal functional deficits) and Function Dominant group (slightly older, 68% runners, more structural changes) both achieved functional recovery by 6 months despite persistent symptoms. The Psychosocial Dominant group (more females, 31% runners, elevated kinesiophobia, reduced quality of life) demonstrated greatest symptom impairment without achieving functional recovery. The Structure Dominant group (predominantly older obese males, severe structural pathology) showed delayed improvement and was the only subgroup failing to achieve structural recovery at 6 months.
Critically, no subgroup achieved complete recovery across all domains at 6 months, highlighting tendinopathy complexity and the need for longer treatment durations and subgroup-specific interventions. The psychosocial dominant group particularly warrants integrated psychological support alongside physical rehabilitation.

Metabolic Risk Factors

Patients with ≥2 metabolic risk factors demonstrate worse symptoms with loading, smaller Achilles tendon cross-sectional area relative to body size, and reduced lower limb function. While these patients continue improving with exercise, they fail to reach equivalent outcomes as low-risk patients. This suggests metabolic dysfunction represents a distinct pathophysiological mechanism, possibly involving altered collagen synthesis, impaired microvascular function, or systemic inflammation, requiring longer rehabilitation periods, modified loading protocols, and concurrent metabolic optimization.

Exercise Prescription and Loading Principles

Exercise-based rehabilitation maintains the highest level of evidence for tendinopathy treatment, with mechanical loading or tendon strain as the critical therapeutic element. Published progression frameworks for Achilles and patellar tendinopathy provide exercise hierarchies based on strain magnitude, allowing systematic rehabilitation progression.
The validated pain monitoring model permits pain ≤5/10 during activity, with modification required for higher pain levels. Research demonstrates that patients using pain-monitored activity (running/jumping) show similar recovery trajectories to those with complete activity restriction, supporting activity continuation rather than complete rest. Limiting activity represents suboptimal management; controlled loading under pain monitoring facilitates recovery without harm.

Neuromuscular Electrical Stimulation and ­Adjunct Treatments

Patellar tendinopathy patients typically exhibit arthrogenic muscle inhibition, utilizing only 80-85% of muscle capacity. NMES applied during exercises can overcome volitional inhibition, increase muscle recruitment, and enhance tendon strain magnitude. While not first-line therapy, NMES represents a valuable adjunct when muscle inhibition limits effective tendon loading.
Preliminary data on radial pressure wave therapy shows superior short-term outcomes (3 months) when combined with exercise compared to exercise alone, though long-term data suggests treatment convergence. This pattern—early recovery acceleration without changing ultimate prognosis—is consistent with many adjunct therapies.

Clinical Recommendations

Core management principles include progressive mechanical loading using established hierarchies, pain monitoring with the 5/10 threshold, and recognition that structural pathology alters muscle recruitment patterns. Treatment individualization should consider patient subgroup classification, metabolic risk profile, domain-specific impairments, psychological factors, and activity demands. The field requires subgroup-specific protocols, integration of metabolic and psychological interventions, and longer follow-up studies to identify complete recovery determinants. While mechanical loading remains the therapeutic foundation, optimizing individual recovery requires comprehensive assessment and tailored intervention strategies addressing the multi-factorial nature of this complex pathology.

References

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