Kraushaar, J Bone Joint Surg Am 1999 - Current Concepts Review - Tendinosis of the Elbow (Tennis Elbow). Clinical Features and Findings of Histological, Immunohistochemical, and Electron Microscopy Studies - Article Summary

Current Concepts Review - Tendinosis of the Elbow (Tennis Elbow). Clinical Features and Findings of Histological, Immunohistochemical, and Electron Microscopy Studies

Kraushaar, Nirschl·J Bone Joint Surg Am·1999·701 citations·Review article

This current concepts review examines the true nature of lateral tennis elbow. The authors studied nine operative specimens using histology, immunohistochemistry, and electron microscopy, comparing them with ten cadaveric controls. Their question: is tennis elbow an inflammatory tendinitis or a degenerative tendinosis, and what should that mean for treatment?

Key Findings

Tennis elbow is a degenerative process, not an inflammatory one. Specimens consistently lacked neutrophils, and macrophages and lymphocytes were scarce or absent. The correct term is tendinosis, not tendinitis or epicondylitis.
The defining histology is angiofibroblastic hyperplasia: fibroblastic hyperplasia, vascular hyperplasia, and disorganized collagen. These are the three fundamental elements of the disease and drive both diagnosis and the rationale for debridement surgery.
The lesion sits at the origin of the extensor carpi radialis brevis, with about one-third of patients also showing involvement of the extensor digitorum communis origin. Know the ECRB as the answer to the classic anatomy question.
The vascular hyperplasia is deceptive. Despite smooth muscle and elastin in vessel walls, the authors could find no vessels with actual blood flow. This explains why the tissue does not heal on its own and why increased vascularity does not mean better healing.
Electron microscopy showed collagen fibrils that were fragmented, of variable diameter, and lacked cross-linkage, structurally unable to sustain a tensile load. The core defect is failed extracellular alignment and cross-linking, not a shortage of collagen.
Myofibroblasts with contractile elements, cells not native to healthy tendon, were present, supporting the model that injured tenocytes dedifferentiate into pluripotent mesenchymal cells capable of vascular, chondroid, osseous, and adipose metaplasia.
A single corticosteroid injection reduced pain at 6 weeks but showed no benefit over placebo at 3 months or 1 year in a randomized trial of 60 elbows. Steroids do not alter the underlying pathology.
Surgery that resects the dull, gray, soft pathologic tissue and induces local bleeding produced good outcomes; only about 25% of a complex referral population and an estimated under 5% of general-practice patients need an operation.

Board PearlTennis elbow is tendinosis, not tendinitis — a degenerative angiofibroblastic process at the ECRB origin with no inflammatory cells, so treat it with resistance exercise, not steroids.

Core

Current Concepts Review - Tendinosis of the Elbow (Tennis Elbow). Clinical Features and Findings of Histological, Immunohistochemical, and Electron Microscopy Studies

Kraushaar, NirschlJ Bone Joint Surg Am1999701 citationsReview article