Anatomy & Organs

Thumb – structure, function & diseases


The thumb is the most mobile finger on the human hand and is indispensable for gripping movements. The mobility of the thumb is mainly due to the thumb saddle joint , which is similar to a ball and socket joint. Pain in this area is one of the most common causes of osteoarthritis .

What is the thumb

The thumb is the shortest and also the first finger on the radial side of the hand. It is given a special position among the fingers because it can be placed opposite the other fingers and is made up of only two bones. The mobility of the thumb exceeds the mobility of all other fingers, which are each made up of three bones .

Why the thumb, unlike the other four fingers of the hand, contains only two finger bones has not yet been conclusively explained. The thumb owes its flexibility to its two-jointed anatomy. It mainly plays a role in gripping movements. The brain area associated with the thumb is far more developed than the areas associated with the other fingers. The term thumb comes from the Germanic language and originally means something like “the strong” or “the fat”.

Anatomy & Structure

The thumb consists of the phalanx proximalis and the phalanx distalis. The phalanx proximalis, on the other hand, is close to the body. The thumb saddle joint (Articulatio carpopetacarpalis pollicis) and the thumb base joint (Articulatio metacarpophalangealis pollicis) give the finger maximum mobility. The thumb saddle joint lies in a sheath of sinewy connective tissue and is supported and stabilized at work by numerous tendons , muscles and ligaments .The protective cover made of connective tissue protects the vessels and nerves of the saddle joint from injuries during forearm muscle contraction. The thumb musculature consists of numerous muscles, such as the musculus extensor pollicis brevis, the musculus pollicis longus and the musculus abductor pollicis longus, which are active as extensors of the thumb. As flexors, the flexor pollicis brevis muscle, flexor pollicis longus muscle, abductor pollicis brevis muscle, opponens pollicis muscle, and adductor pollicis muscle are associated with the thumb joint.

Function & Tasks

The tasks of the thumb result primarily from its ability to face the other fingers of the respective hand. The thumb is able to do this primarily thanks to the thumb saddle joint, which optimizes the gripping functions of the hand. The thumb saddle joint lies between the great polygon and the metacarpal and has inwardly inclined and outwardly inclined sections.

The bones of the thumb can thus be moved back and forth as well as from side to side. Even rotations are limited with the thumb. The thumb saddle joint is similar to your ball and socket joint in that it can move on two axes. Unlike the other fingers, the thumb can mainly exert counter-pressure on the other fingers due to these anatomical peculiarities. This allows the hand to be closed in a firm grip. The pronounced musculature in the ball of the thumb allows gripping movements of different strengths. The thumb muscles are also known as the thenarm muscles and correspond to four different muscles that attach to the carpal bone and form the thenar eminence.

Grasping movements are everyday movements that humans find difficult to do without. Certain objects are grabbed dozens of times a day. Without the thumb, it would only be possible to a limited extent to grasp objects, hold them and carry them from A to B in a grip. Expressions such as “everything under control” prove how crucial a firm grip is for people. The thumb has also made it into numerous idioms due to its crucial functions in everyday life, such as the expression “pi mal thumb”.

Thumb pain is common and can have a variety of causes. In the case of rhizarthrosis, for example, stress-dependent pain occurs between the thumb and wrist . Arthrosis of the thumb saddle joint is one of the most common causes of pain in this area and, as a degenerative phenomenon, affects older people in particular.Due to the numerous tendons near the thumb, tendonitis is also a common clinical picture. Special forms of such inflammation are the housewife’s thumb and the snap thumb, both of which arise from an overload. Sometimes thumb pain is also a symptom of a ganglion, i.e. ganglion, which is usually on the extensor side of the thumb. Rarely, ganglions lie on the crook of the thumb, where they are usually smaller. A snap thumb may develop from a ganglion. Thumb injuries caused by overloading can also be responsible for thumb pain, for example in the case of the ski thumb, where there is a rupture of the collateral ligament.

The thumb can also be affected by conditions such as gout and arthritis . In arthritis, pain is usually accompanied by swelling , which can be reactive, infectious, or chronic. Necrosis and bone cysts are also conceivable in the thumb, but are far less common than overloading, arthroses or arthritic symptoms.

Thumb pain often limits the mobility of the thumb. Due to the crucial functions of the thumb in everyday life, this can severely limit those affected and thus reduce the quality of life. The prognosis is good for most diseases of the thumb. However, arthritis, arthrosis and gout can be expected to cause long-term symptoms, which may have to be counteracted with painkillers .

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.