The human hand is an intricate structure, allowing for a vast range of movements from powerful grips to delicate, precise actions. This dexterity relies heavily on a complex network of tissues, among which tendons play a central role. Tendons connect muscles to bones, translating muscle contractions into daily movements. Understanding these structures helps appreciate the hand’s capabilities.
Counting Hand Tendons
A typical human hand, including the wrist, contains approximately 24 major tendons that enable its diverse movements. These cord-like tissues are composed of dense fibrous connective tissue, linking muscles in the forearm to bones within the hand and fingers. The precise number can vary slightly between individuals due to anatomical differences, such as the presence or absence of the palmaris longus tendon. These tendons are categorized into two main groups based on their primary function: those that bend parts of the hand and those that straighten them.
The Hand’s Tendon Teams
The hand’s movements are managed by two primary categories of tendons: flexor tendons and extensor tendons.
Flexor tendons are on the palm side of the hand and wrist, responsible for bending the fingers, thumb, and wrist. This group includes tendons like the flexor digitorum profundus and superficialis, which bend the finger joints, and the flexor pollicis longus for thumb bending. Other flexor tendons contribute to wrist flexion. These 12 flexor tendons enable gripping, grasping, and making a fist.
On the back of the hand and wrist are the extensor tendons. Their function is to straighten the fingers, thumb, and extend the wrist. This team includes tendons such as the extensor digitorum communis for the main fingers, and others providing independent extension for the index and little fingers. The thumb’s extension is managed by several extensor pollicis tendons. Other extensor tendons facilitate wrist extension. The coordinated action of these 12 extensor tendons allows for opening the hand and precise finger adjustments.
When Tendons Face Trouble
Despite their strength, hand tendons can encounter various issues, often leading to pain and reduced function. Tendonitis refers to the inflammation of a tendon, caused by overuse, repetitive movements, or direct trauma. Symptoms include localized pain, swelling, and difficulty moving the affected area. This condition can impact any tendon in the hand or wrist, affecting daily activities.
A related condition is tenosynovitis, which involves inflammation of both the tendon and its protective sheath. A common example is De Quervain’s tenosynovitis, affecting the two tendons on the thumb side of the wrist. This type often results from repetitive hand and wrist motions, and can cause pain, swelling, and a “sticking” sensation when moving the thumb. Overuse, injury, or underlying conditions like rheumatoid arthritis can contribute to both tendonitis and tenosynovitis.
More severe issues include tendon ruptures, which are partial or complete tears of the tendon. These can occur due to sudden forceful movements, trauma, or progressive weakening over time. A rupture can lead to immediate pain, swelling, and an inability to move the affected finger or part of the hand. Persistent hand pain, swelling, or loss of movement warrants evaluation by a medical professional for proper diagnosis and guidance.