A hinge joint, also known as a ginglymus, is a joint in the bones of an animal or person that allows movement in one direction. Hinge joints include ankles, elbows, fingers, knees, and toes. These joints are formed when two or more bones meet and move along an axis to bend. Consider how our elbows bend when we lift a glass or how our fingers curl when we make a fist.
Hinge joints are assisted by other tissues, including cartilage and ligaments, to connect and bend. These connective tissues protect the bones from rubbing as they bend at varying degrees to keep our bodies mobile. Let's explore various hinge joint examples.
The elbow joint connects the upper portion of the arm (humerus) to the two bones in the lower arms (radius and ulna). Thus, it's called the humeroulnar joint in the medical community. The humeroulnar joint is located between a notch in the ulna and a notch in the humerus.
Although the jaw is primarily a hinge joint - allowing you to open and close your mouth - it can also move from side to side. The jawbone itself isn't a hinge joint, but it is the part that moves as a result of the hinge. Like the knee and ankle joints, it can also exhibit a certain amount of rotary movement which is characteristic of a number of other types of joints, such as the ball and socket joints.
Interphalangeal joints are the joints that connect our fingers together. These might be some of the most important hinge joints in the human body, considering how much we use our hands on any given day. There are three sets of joints in our hands.
The metacarpophalangeal joints are hinge joints between the hand and the start of each finger. Metacarpo refers to the metacarpal bones that make up the main part of the hand, between the wrist and fingers.
The proximal interphalangeal joints are the joints that are located in between the first and second phalanges, or finger bones. This joint has great lateral stability. Proximal interphalangeal joints are located in the middle of the finger. This joint uses the term "proximal" because it is closer to the rest of the body.
The distal interphalangeal joints are hinge joints between the second and third phalanges, or finger bones. These joints are the ones closest to the tips of the fingers. This joint uses the term "distal" because it's the farthest away from the body.
Like our hands, our feet also have three interphalangeal joints. These joints have an underside consisting of two plantars (the plantar fascia and the plantar calcaneonavicular) and other ligaments and tendons.
While your toes certainly look different from your fingers, they work in much the same way and exhibit the same two movements - flexion and extension. It's also interesting to note that the foot has a metatarsophalangeal joint at the base of each toe, connecting the metatarsals (foot bones) with the phalanges (toe bones), just like how your hands have metacarpophalangeal joints.
The knee joint attaches our thighs to our lower legs. Because it's the largest joint in the human body, it's a relatively complicated joint to understand in terms of connection and motion. The knee is different from other hinge joints, except for the ankle, because it allows for slight side-to-side movement rather than simply flexion and extension.
Your ankle joint is another type of hinge joint. Known as the talocrural region, this joint is responsible for the motion of your feet at the ankles. Like the knee joint, this hinge joint is rather unique in that it allows for some side to side movement. In fact, the hinge joint of the ankle is made up of three separate joints:
The talocrural joint takes care of the front to back motion.
The subtalar joint allows for inversion and eversion of the foot. Inversion is the movement toward the inside of the leg, which allows you to rest on the outside edge of the foot. Eversion is the opposite - it lets you rest your foot on the inside edge, where the big toe is located.
The distal tibiofibular joint allows limited movement of the foot. It works with the movements at the ankle joint.
Can you imagine our bodies without hinge joints? Take some time to notice the speed with which we type on our keyboards or the slight bend in our knees as we workout. Science is everywhere, inside our bodies and in our external environment.
Take a look at these Examples of Observation to increase your knowledge of the scientific method. Who knows? Maybe your interest in hinge joints is an indication of your future in the medical field!