The thumb is the most mobile finger of the human hand and irreplaceable for grasping movements. The thumb gets its mobility primarily from the thumb saddle joint, which is close to a ball-and-socket joint. Pain in this area is among the most common due to osteoarthritis.
What is the thumb?
The thumb is the shortest and also the first finger on the radial side of the hand. Among the fingers, it is accorded a special position because it can be placed opposite the other fingers and is composed of only two bones. The mobility of the thumb exceeds the mobility of all other fingers, which are built from three bones each. Why the thumb, unlike the other four fingers of the hand, contains only two phalanges has not yet been conclusively explained. The thumb owes its flexibility to its two-jointed anatomy. It plays a role above all for grasping movements. The brain area assigned to the thumb is far more pronounced than the areas assigned to the other fingers. The term thumb originates from Germanic and originally means something like “the strong one” or “the fat one”.
Anatomy and structure
The thumb consists of the phalanx proximalis and the phalanx distalis. The phalanx proximalis, on the other hand, is located near the body. The thumb saddle joint (Articulatio carpometacarpalis pollicis) and the thumb metacarpophalangeal joint (Articulatio metacarpophalangealis pollicis) give the finger its greatest mobility. The thumb saddle joint lies in a sheath of sinewy connective tissue and is supported and stabilized in its work by numerous tendons, muscles and ligaments. The protective sheath of connective tissue protects the vessels and nerves of the saddle joint from injury during 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. As flexors, 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 associated with the thumb joint.
Function and tasks
The thumb’s tasks derive primarily from its ability to oppose the other fingers of the respective hand. The thumb is capable of this mainly thanks to the thumb saddle joint, which optimizes the gripping functions of the hand. The thumb saddle joint is located between the large polygonal bone and the metacarpal bone and has inwardly inclined and outwardly inclined sections. This allows the bones of the thumb to move back and forth as well as from side to side. Even rotations are possible for the thumb to a limited extent. The thumb saddle joint has similarities to your ball and socket joint in that it can move on two axes. Unlike the other fingers, the thumb can primarily exert counterpressure on the rest of the fingers because of these anatomical features. This allows the hand to be closed into a firm grip. The pronounced musculature in the ball of the thumb allows gripping movements of varying strength. The thumb muscles are also called thenar 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 find difficult to do without. We reach for certain objects several dozen times a day. Without the thumb, it would be possible only to a limited extent to grasp objects, hold them and move them from A to B in a firm grip. How decisive the firm grip is for humans is proven by phrases such as “everything under control”. The thumb has also made it into numerous idioms because of its crucial functions in everyday life, such as the expression “pi times thumb.”
Diseases
Pain in the thumb is common and can have a variety of causes. In rhizarthrosis, for example, load-dependent pain occurs between the thumb and wrist. This thumb saddle joint arthrosis is one of the most common causes of pain in this area and, as a degenerative condition, mainly affects older people. Due to the numerous tendons near the thumb, tendon sheath inflammation is also a frequent clinical picture. Special forms of such inflammations are housewife’s thumb and snap thumb, both of which arise from overuse. Sometimes thumb pain is also the symptom of a ganglion, i.e., hyperphaly, which is usually located on the extensor side of the thumb.More rarely, overbones are located on the flexor latitude of the thumb, where they are usually smaller. A supra-leg may develop into a snapping thumb under certain circumstances. Thumb injuries from overuse can also be responsible for thumb pain, such as in the case of 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 may be reactive, infectious, or chronic. Necrosis and bone cysts are equally conceivable in the thumb, but occur far less frequently than overloading, osteoarthritis, or arthritic manifestations. Thumb pain often limits the mobility of the thumb. This can severely limit sufferers because of the thumb’s crucial functions in daily life, reducing quality of life. Most diseases of the thumb have a good prognosis. However, arthritis, osteoarthritis and gout suggest prolonged discomfort that may need to be managed with pain medications.
