original abstract†Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.
Tendon disorders are a major problem for participants in competitive and recreational sports. To try to determine whether the histopathology underlying these conditions explains why they often prove recalcitrant to treatment, we reviewed studies of the histopathology of sports-related, symptomatic Achilles, patellar, extensor carpi radialis brevis and rotator cuff tendons. The literature indicates that healthy tendons appear glistening white to the naked eye and microscopy reveals a hierarchical arrangement of tightly packed, parallel bundles of collagen fibres that have a characteristic reflectivity under polarised light. Stainable ground substance (extracellular matrix) is absent and vasculature is inconspicuous. Tenocytes are generally inconspicuous and fibroblasts and myofibroblasts absent. In stark contrast, symptomatic tendons in athletes appear grey and amorphous to the naked eye and microscopy reveals discontinuous and disorganised collagen fibres that lack reflectivity under polarised light. This is associated with an increase in the amount of mucoid ground substance, which is confirmed with Alcian blue stain. At sites of maximal mucoid change, tenocytes, when present, are plump and chondroid in appearance (exaggerated fibrocartilaginous metaplasia). These changes are accompanied by the increasingly conspicuous presence of cells within the tendon tissue, most of which have a fibroblastic or myofibroblastic appearance (smooth muscle actin is demonstrated using an avidin biotin technique). Maximal cellular proliferation is accompanied by prominent capillary proliferation and a tendency for discontinuity of collagen fibres in this area. Often, there is an abrupt discontinuity of both vascular and myofibroblastic proliferation immediately adjacent to the area of greatest abnormality. The most significant feature is the absence of inflammatory cells. These observations confirm that the histopathological findings in athletes with overuse tendinopathies are consistent with those in tendinosis--a degenerative condition of unknown aetiology. This may have implications for the prognosis and timing of a return to sport after experiencing tendon symptoms. As the common overuse tendon conditions are rarely, if ever, caused by 'tendinitis', we suggest the term 'tendinopathy' be used to describe the common overuse tendon conditions. We conclude that effective treatment of athletes with tendinopathies must target the most common underlying histopathology, tendinosis, a noninflammatory condition.
These three articles on PainScience.com cite Khan 1999 as a source:
- PS Save Yourself from IT Band Syndrome! — All your treatment options for Iliotibial Band Syndrome reviewed in great detail, with clear explanations of recent scientific research supporting every key point
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- PS Repetitive Strain Injuries Tutorial — Five surprising and important facts about repetitive strain injuries like carpal tunnel syndrome, tendinitis, or iliotibial band syndrome
This page is part of the PainScience BIBLIOGRAPHY, which contains plain language summaries of thousands of scientific papers & others sources. It’s like a highly specialized blog. A few highlights:
- Effectiveness of customised foot orthoses for Achilles tendinopathy: a randomised controlled trial. Munteanu 2015 Br J Sports Med.
- A Bayesian model-averaged meta-analysis of the power pose effect with informed and default priors: the case of felt power. Gronau 2017 Comprehensive Results in Social Psychology.
- The neck and headaches. Bogduk 2014 Neurol Clin.
- Agreement of self-reported items and clinically assessed nerve root involvement (or sciatica) in a primary care setting. Konstantinou 2012 Eur Spine J.
- Effect of NSAIDs on Recovery From Acute Skeletal Muscle Injury: A Systematic Review and Meta-analysis. Morelli 2017 Am J Sports Med.