thumb

Of the thumb is the most agile finger of the human hand and irreplaceable for grasping movements. The thumb gets its mobility mainly from the thumb saddle joint, which is close to a ball 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 under the fingers because it can be compared to 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 made up of three bones each.

Why the thumb, unlike the other four fingers of the hand, only contains two finger bones has not yet been conclusively clarified. The thumb owes its flexibility to its two-jointed anatomy. It plays a role primarily for gripping movements. The brain area assigned to the thumb is by far more pronounced than the areas assigned to the other fingers. The term thumb comes from Germanic and originally means something like "the strong one" or "the fat one".

Anatomy & structure

The thumb consists of the proximal phalanx and the distal phalanx. The phalanx proximalis, on the other hand, is close to the body. The thumb saddle joint (Articulatio carpometacarpalis pollicis) and the thumb base joint (Articulatio metacarpophalangealis pollicis) give the finger maximum mobility. The thumb saddle joint lies in a sheath made of sinewy connective tissue and is supported and stabilized by numerous tendons, muscles and ligaments during work.

The protective covering made of connective tissue protects the vessels and nerves of the saddle joint from injuries caused by forearm muscle contraction. The thumb muscles consist of numerous muscles, such as the extensor pollicis brevis muscle, the pollicis longus muscle and the abductor pollicis longus muscle, which are active as extensors of the thumb. The flexor pollicis brevis muscle, the flexor pollicis longus muscle, the abductor pollicis brevis muscle, the opponens pollicis muscle and the adductor pollicis muscle are connected to the thumb joint as flexors.

Function & tasks

The tasks of the thumb result primarily from its ability to point towards 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 saddle thumb joint lies between the large polygonal bone and the metacarpal bone and has inwardly inclined and outwardly inclined sections.

The bones of the thumb can be moved back and forth as well as from side to side. The thumb can even turn to a limited extent. The thumb saddle joint is similar to your ball joint in that it can move on two axes. Unlike the other fingers, due to these anatomical features, the thumb can primarily exert counter-pressure on the remaining fingers. So the hand can be closed to a firm grip. The pronounced musculature in the ball of the thumb allows gripping movements of various 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 ball of the thumb.

Grasping movements are everyday movements that humans can hardly do without. Certain objects are picked up several dozen times a day. Without the thumb, it would only be possible to grasp objects, hold them and move them from A to B with ease. Sayings 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".

Diseases

Thumb pain is common and can have various causes. In rhizarthrosis, for example, stress-dependent pain occurs between the thumb and wrist. This arthrosis of the thumb saddle joint is one of the most common causes of pain in this area and, as a degenerative phenomenon, particularly affects older people.

Because of the numerous tendons near the thumbs, tendinitis is also a common disease. Special forms of such inflammation are the housewife's thumb and the snap thumb, both of which arise from overload. Sometimes thumb pain is also a symptom of a ganglion, that is, the transverse leg, which is usually on the extensor side of the thumb. Over-legs are less often on the flexion width of the thumb, where they are usually smaller. A snapping thumb may develop from an over leg. Thumb injuries caused by excessive strain can also be responsible for thumb pain, for example in the case of the ski thumb, which has a rupture of the collateral ligament.

The thumb can also be affected by conditions such as gout and arthritis. In arthritis, the pain is usually accompanied by swelling, which can be reactive, infectious, or chronic. Necroses and bone cysts are also conceivable in the thumb, but they occur far less often than overloads, arthrosis or arthritic manifestations.

Thumb pain often restricts the flexibility of the thumb. This can severely curtail those affected because of the crucial functions of the thumb in everyday life and thus reduce the quality of life. The prognosis for most diseases of the thumb is good. Arthritis, osteoarthritis and gout, however, mean that protracted symptoms can be expected, which may have to be countered with painkillers.