Repartition of tendon sheaths in humans

As a medical student I have been taught that tendon sheaths are found predominantly in the wrists, hands and ankles. However, I learned recently that tenosynovitis often affect the biceps brachii. It is confusing me because this implies that the biceps’ tendon also has a sheath.
Can someone tell me where exactly tendon sheats are found in humans ? Are they ubiquitous ?
Many thanks in advance.