De Quervain’s tenosynovitis describes a condition in which 2 of the tendons attached to the thumb become painful and inflamed as they cross the wrist joint at the base of the thumb.
It arises when the 2 tendons ( extensor pollicis brevis and abductor pollicis longus) become inflamed as they cross the wrist joint usually as a result of repetitive activity at the wrist. The 2 muscles are located in the lower forearm and run across the wrist to attach at the thumb. The tendons are contained in a sheath, under normal circumstances they freely slide through to produce the thumb movements needed, but if subject to excessive repetitive activity they become painful and inflamed . It is not known exactly why this occurs but this condition occurs commonly in people doing repetitive activity at the wrist eg bar staff and occurs during pregnancy or post-partum possibly as a result of hormonal changes or excessive lifting of the newborn baby.