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The amazing structure of the human body: How do we keep our fingers stable when bending?
The flexibility and stability of the fingers come from their anatomy, especially the design of the knuckles. Each finger of the hand has two sets of interphalangeal joints, the proximal interphalangeal joint (PIP) and the distal interphalangeal joint (DIP). These joints allow the fingers to bend flexibly and maintain stability.
Each finger has two joints except for the thumb which has one joint.
Anatomically, the PIP and DIP joints have many similarities, especially in the range of motion and structure they provide. While the proximal interphalangeal joint provides a greater range of flexion, the distal interphalangeal joint has relatively less mobility.
Joint structure
The lateral stability of the PIP joint is quite strong, and its lateral diameter is larger than the front and rear diameter. This structure allows it to provide stable support when the finger is bent. In contrast, the volar ligaments provide important stability and prevent hyperextension.
When the fingers are flexed, the volar ligament prevents hyperextension of the joint, thus stabilizing joint movement.
On the dorsal side of the PIP joint, the joint capsule, extensor tendons and skin are relatively thin, which allows the bending between the metacarpal bones to exceed 100°. It can be seen that the elegant design of the finger structure allows us to achieve fine movements.
Dorsal structure
At the level of the PIP joint, the extensor mechanism is divided into three bands. These bands provide the necessary stability during flexion and prevent inappropriate displacement of the joint during flexion. This structure allows the fingers to remain flexible and stable while performing various daily activities.
Parar structure
On the volar side, the structure of the palmar ligament is thicker than that on the dorsal side, which can effectively prevent hyperextension. This part not only provides support, but also resists the compressive forces of the interphalangeal joint through its structure. This design not only protects the joints, but also maintains their stability during different movements.
The metacarpal ligament not only provides stability when the fingers are bent, but also increases the moment arm of the flexor muscles, making the fingers more powerful.
Range of motion
Among the movements of the interphalangeal joints, the only movements allowed are flexion and extension. The PIP joint has a flexion range of about 100°, while the DIP joint is slightly more limited, about 80°. This reality allows us to precisely control the movements of our fingers when performing delicate operations.
Clinical significance
Clinically, rheumatoid arthritis usually spares the distal interphalangeal joints, and this feature can help doctors determine whether other types of arthritis are present, such as osteoarthritis or psoriatic arthritis. The impact of these diseases on the fingers is not limited to pain, but may also affect the flexibility and function of the fingers.
Summary
The flexibility and stability of our fingers stem from their exquisite anatomical structure, from the design of joints to the configuration of ligaments, which provide the necessary support for our fingers. After all, how will the study of these structures impact our understanding of hand injuries and diseases in future medical research?
