A tendon is a fibrous tissue that connects a muscle to a bone.  When a tendon is injured, damaged or inflamed, in medical lexicon it is referred to by names such as tendinitis, tendinosis, tendinopathy, paratenonitis, tenosynovitis, and tendon tear (rupture).  Tendinitis and tendinosis are two medical terms which may sound identical and often both are confused with other, but in actuality both are different.  Tendinosis is a condition that is characterized by pain of a tendon, whereas tendinitis is a condition which shares many of the same symptoms but varies vastly in its cause and appearance.

Main difference between tendinosis and tendinitis is time.  Tendinosis is a persisting and recurring condition caused by repetitive trauma or an injury that hasn’t healed completely.  However, tendinitis is an abrupt short-term condition in which inflammation is the result of a direct injury to a tendon.  An easy way to distinguish the two is to understand the difference in their suffixes, with “osis” referring to abnormal or disease and “itis” meaning inflammation.

Apart from that there are greater differences in the symptoms and pattern of the two conditions.

Tendinosis:  Tendinosis does not involve swelling.  In fact it is a non-inflammatory degeneration of a tendon.  This may cause changes to structure or composition of the tendon.  These changes often stem from repetitive strain-injuries to a tendon without adequate time to heal.  In tendinosis, tendons are chronically damaged with disorganized fibers and a hard, thickened, scarred and rubbery appearance.  Though it could be painful, there may not be redness or warmth of the adjacent soft tissues.  When examined under a microscope, micro-tears of the tendon may be visible, but there would be no evidence of inflammatory cells.  People who engage in high-intensity activities or sports requiring repeated tendon movement often get affected by tendinosis

Tendinitis:  By contrast, tendinitis involves inflammation and that is evidenced by swelling, redness and warmth in addition to pain.  Acute injury or repeated micro-traumas to a tendon or group of tendons are called tendinitis. When observed under microscope, inflammatory cells can be seen, but there may not be microscopic tendon damage.  Tears and damage would be more prominent in tendinitis.  Tears happen when tendons are overloaded with a tensile force that is too heavy and/or too sudden.  Tendinitis is a more common diagnosis compared to tendinosis and chronic tendinitis may lead to tendinosis.  Treatment for the condition may involve over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen. Patients with tendonitis typically recover within several weeks.

These fundamental differences inform how the treatment of the two conditions should be made and predict the outcome.  It is important for healthcare practitioners to distinguish between these two disorders in order to apply the most appropriate treatment.

Tendinosis occurs as a result of degeneration due to chronic overuse.  As the overuse continues, the tendon does not get the time to heal and rest, such as with repetitive strain injury.  Seemingly innocuous movements, such as moving a mouse can lead to tendinosis when done repeatedly over a long period of time.

The confusion between tendinosis and tendinitis is widespread.  Many injuries that are presumed to be tendinitis can actually be tendinosis if the injury is deep, for e.g. tennis elbow.  The primary reason to distinguish between tendinosis and tendinitis is the different treatment methods to be adopted to treat the condition, which invariably involve different timelines as well.  The most prominent treatment goal for tendinitis is to bring down the level of inflammation, a condition that is not present in tendinitis.

The healing time required for tendinitis is relatively shorter, depending on whether treatment starts with early presentation or after the condition aggravated.  However, the treatment for tendinosis may range anywhere between three to six months.  If the tendinosis is chronic, it may take upto nine months for complete recovery.  Treating a chronic tendinosis for a matter of weeks would not provide any great benefit in long-term repair of the affected tendon.  Knowing these timelines is actually an integral part of choosing an appropriate treatment modality.

Treatment for tendinosis is more long-term and structural in nature like breaking the cycle of injury, optimizing connective tissue (collagen) production, tendon thickening, rest, adjust ergonomics, use appropriate support, apply ice, message, nutrition etc.

Comparison factor Tendinitis Tendinosis
Recovery time in acute cases Two to three days Two to three months
Recovery time in chronic cases Four to six weeks Three to nine months
Long-term outlook with non-surgical treatment Almost 99% recover completely Upto 80% cases recover completely
Treatment goals Decrease inflammation by: Rest, anti-inflammatory medication (short-term course), icing the tendon intermittently, and/or use of cast or splint Encourage formation of collagen and other proteins by: Physical therapy, exercise, and/or surgery (in some cases)
Long-term outlook after surgery Almost 95% of cases recover after surgery 70 to 85% of cases recover after surgery
Recovery time after surgery Three to four weeks Four to six months
Underlying cause Inflammation Degeneration


It is important to make a clear-cut distinction between tendinitis and tendinosis when there is a tendon damage as the ultimate treatment can be very different.

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