Can Tendinitis Start Suddenly?
No, true tendinitis rarely starts suddenly—most cases presenting in primary care are chronic degenerative conditions (tendinosis) that develop gradually from repetitive loading, not acute inflammatory processes. 1
Understanding the Terminology and Pathophysiology
The term "tendinitis" is commonly misused in clinical practice. Acute inflammatory tendinopathies do exist, but the vast majority of patients seen in primary care have chronic symptoms indicating a degenerative condition that should be labeled "tendinosis" or "tendinopathy" rather than "tendinitis." 1
How Tendon Problems Actually Develop
The natural history is gradually increasing load-related localized pain coinciding with increased activity, not sudden onset. 1
Tendon injury occurs from repetitive strain and loading where the tendon is strained repeatedly to 4-8% strain until unable to endure further tension. 2
Structural damage develops as collagen fibers slide past one another, causing breakage of their cross-linked structure, leading to denaturation, inflammation, edema, and pain. 2
The tendon becomes fatigued as its basal reparative ability is overwhelmed by repetitive dysfunctional and microtraumatic processes. 3
When Sudden Onset Does Occur
While chronic tendinopathy is the norm, there are specific scenarios where tendon problems can present acutely:
Tears can occur in healthy tendons that are acutely overloaded during high-speed or high-impact events. 4
Acute tendon ruptures (not tendinitis) can happen suddenly, particularly in the Achilles tendon. 4
Laceration injuries represent another form of acute tendon damage, but this is traumatic injury rather than tendinitis. 4
Clinical Implications for Diagnosis
Physical examination typically reveals well-localized tenderness that reproduces the pain experienced during activity, consistent with a chronic process. 5, 6
The pathophysiology progresses on a continuum from reactive tendinopathy (tenocyte proliferation, protein production increase, tendon thickening) to tendon disrepair (focal collagen fiber disruption) to degenerative tendinopathy (cell death, collagen disorganization). 7
Inflammation may be present, especially in early phases, but this does not mean the condition started suddenly—it represents the body's response to accumulated microtrauma. 7
Common Pitfall to Avoid
Misdiagnosing chronic degenerative tendinosis as acute inflammatory "tendonitis" leads to inappropriate treatment focus, particularly overreliance on anti-inflammatory medications that provide only short-term relief without addressing the underlying degenerative process. 6