Tendons are a crucial element of the musculoskeletal system. They are formed from tough connective tissue fibers that connect muscle to bone, thus allowing muscle contractions to produce skeletal movement. Tendons are covered with a sheath called the tenosynovium. This sheath is filled with a liquid called synovial fluid, which allows the tendon to slide easily through the tenosynovium when the muscle contracts. Flexors are muscles that cause bending of a joint, as opposed to extensors, which straighten a joint. When the tenosynovium of a flexor becomes irritated and inflamed, a condition called flexor tenosynovitis results. A number of symptoms are commonly associated with flexor tenosynovitis.
Trigger Finger
Flexor tenosynovitis is most commonly used to describe symptoms affecting the tendons of the hand. Trigger finger is a condition wherein the synovium of the finger or thumb flexor tendons becomes inflamed to such a degree that the tendon cannot slide freely within it. As a result, the finger remains in a bent position. The New York University Langone Medical Center explains that in less severe cases, the finger may still be extended, resulting in a popping sound. When trigger finger symptoms are more extreme, it may be impossible for the patient to extend his finger.
Pain
Tenosynovitis of the flexor tendons commonly causes pain in the affected joint. In some cases, Dr. Ryan Keith Weakley, of the University of South Florida, explains that flexor tenosynovitis can result from an infection in the joint. Infection of the tendon sheath can cause swelling and pain. In other cases, overuse of the joint or injury is responsible for the pain experienced due to flexor tenosynovitis. This pain will be present upon any attempt to straighten the joint and will be traceable along the length of the tendon when the finger is extended.
Swelling
Wheeless' Textbook of Othopaedics explains that swelling that affects the entire finger is one of the four cardinal signs of infectious tenosynovitis. These are signs that are used to distinguish infectious tenosynovitis from other forms of localized infection.
When the immune system senses an injury or infection, it releases histamines, chemicals that increase the permeability of the blood vessels. This allows fluids containing white blood cells to flow out of the blood vessels and into the affected tissue. As this fluid gathers in the joint affected by tenosynovitis, swelling can result.
