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For example, when standing up, the knees are extended. When a joint can move forward and backward, such as the neck and trunk, extension is movement in the posterior direction. [10] Extension of the hip or shoulder moves the arm or leg backward. [11] Even for other upper extremity joints – elbow and wrist, backward movement results in extension.
Range of motion (or ROM) is the linear or angular distance that a moving object may normally travel while properly attached to another.. In biomechanics and strength training, ROM refers to the angular distance and direction a joint can move between the flexed position and the extended position. [1]
According to one classification system, a pivot joint like the other synovial joint —the hinge joint has one degree of freedom. [1] Note that the degrees of freedom of a joint is not the same as a joint's range of motion.
A multiaxial joint (polyaxial joint or triaxial joint) is a synovial joint that allows for several directions of movement. [9] In the human body, the shoulder and hip joints are multiaxial joints. [10] They allow the upper or lower limb to move in an anterior-posterior direction and a medial-lateral direction.
The knee joints and ankle joints are less typical, as they allow a slight degree of rotation or of side-to-side movement in certain positions of the limb. The knee is the largest hinge joint in the human body. Hinge and pivot joints are both types of synovial joint. A hinge joint can be considered a modified sellar/saddle joint, with reduced ...
Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed (bent) elbow. Straightening of the arm would require extension at the elbow joint. If the head is tilted all the way back, the neck is said to be extended.
Regarding posture, a pronated foot is one in which the heel bone angles inward and the arch tends to collapse. Pronation is the motion of the inner and outer ball of the foot with the heel bone. [13] One is said to be "knock-kneed" if one has overly pronated feet. It flattens the arch as the foot strikes the ground in order to absorb shock when ...
By being so shallow the glenoid cavity allows the shoulder joint to have the greatest mobility of all joints in the body, allowing 120 degrees of unassisted flexion. Additional range of motion in shoulder flexion (typically up to 180 degrees in humans) is also accomplished by the great mobility of the scapula (shoulder blade) through a process ...