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.