Each of these wedge-shaped crescents of knee joints have shock absorbers that resist impacts when running, jumping, etc.
Violent rotational movements of the thighs or legs while the knee joints are flexed; as in, football, soccer, skiing, or other sports, can severely damage the menisci or cartilage disks when they are squeezed between the bones of the knee joints.
The lateral menisci of the knees are toward the outer sides of the knee couplings and they serve to evenly load the surfaces during the body's weight-bearing, and also aid in providing fluids for the lubrications of the contacting points.
The medial menisci of the knees provide outer curves for conjoining links to move on, serve to evenly load the structures during walking, and aid in disbursing fluids to the joints for lubrication of those skeletal parts.
The term, knee-jerk, often has a negative connotation; such as, being too-hasty, to impulsive, and perhaps even being an irrational or unacceptable response.