Tendinitis: Rare. Inflammatory condition involving a tendon (the structure that attaches muscle to bone). Usually resolves fully within a few weeks.
Tendinosis: Common. Degeneration of a tendon that occurs in the absence of inflammation. Often becomes a chronic condition lasting for weeks, months, even years.
Both tendinitis and tendinosis result from overuse. Common locations for the conditions are the Achilles tendon, knee, ankle, hip, and shoulder. Arguing the semantics may not seem worthwhile to you, but when it comes to treatment, the correct terminology may mean the difference between recovering and not.
Treatment for tendinitis focuses on reducing inflammation. Anti-inflammatory strategies include medication, rest, ice, and electric stimulation. Tendinosis, on the other hand, is not an inflammatory condition so the aforementioned strategies will not work to fix the problem. Tendinosis is degenerative (the tissue is dying), so treatment emphasis must be on regeneration. These strategies include restoring blood flow, reducing tension, and improving mechanics.
Unfortunately many people with tendinosis receive an improper diagnosis. If their “tendinitis” has been present for more than a few weeks and isn’t responding to rest, ice, and medication, the problem likely isn’t tendinitis. Instead, tendinosis is the probable injury and a completely different treatment paradigm is necessary.