The place where the extensor tendon attaches to the middle phalanx is called the central slip. The extensor hood flattens out to cover the top of the finger and sends out branches on each side that connect to the bones in the middle and end of the finger. As they travel into the fingers, the extensor tendons become the extensor hood. These muscles travel towards the hand, where they eventually connect to the extensor tendons before crossing over the back of the wrist joint.
The extensor tendons of the fingers begin as muscles that arise from the backside of the forearm bones. The tendons that allow each finger joint to straighten are called the extensor tendons. Finger deformities can occur when the volar plate loosens from disease or injury. The ligament tightens as the joint is straightened and keeps the PIP joint from bending back too far (hyperextending). This ligament connects the proximal phalanx to the middle phalanx on the palm side of the joint. In the PIP joint (the middle joint between the main knuckle and the DIP joint), the strongest ligament is the volar plate. The function of the collateral ligaments is to prevent abnormal sideways bending of each joint. Two important structures, called collateral ligaments, are found on either side of each finger and thumb joint. Ligaments are tough bands of tissue that connect bones together.
There is articular cartilage essentially everywhere that two bony surfaces move against one another, or articulate. The function of articular cartilage is to absorb shock and provide an extremely smooth surface toįacilitate motion. This white, shiny material has a rubbery consistency. The joints of the hand, fingers, and thumb are covered on the ends with articular cartilage. The IP joints of the digits also work like hinges when you bend and straighten your fingers and thumb. The thumb only has one IP joint between the two thumb phalanges. The joint near the end of the finger is called the distal IP joint (DIP joint). The one closest to the MCP joint (knuckle) is called the proximal IP joint (PIP joint). The three phalanges in each finger are separated by two joints, called interphalangeal joints (IP joints). The MCP joints work like a hinge when you bend and straighten your fingers and thumb. These joints are called the metacarpophalangeal joints (MCP joints). The main knuckle joints are formed by the connections of the phalanges to the metacarpals. Small bone shafts called phalanges line up to form each finger and thumb. One metacarpal connects to each finger and thumb. There are five metacarpals forming the palm of the hand. Further into the palm, the carpals connect to the metacarpals. The carpals join with the two forearm bones, the radius and ulna, forming the wrist joint. The wrist itself contains eight small bones, called carpals. There are 27 bones within the wrist and hand.