"Don't be afraid to take a big step if one is indicated; you can't cross a chasm in two small jumps." —David Lloyd George, 1863-1945, British politician and prime minister of United Kingdom
By the end of this chapter, you should be able to:
Identify the bones, joints, soft tissue, and muscles of the knee;
Discuss the relationship between the tibiofemoral and patellofemoral joints and their contribution to functional movement;
List muscles that are prime movers of the knee;
Discuss the influence of gravity and body position in determining muscles acting on the knee during functional motions;
Name muscle groups that function to position and move the knee in specific functional activities;
Describe commonly encountered movement disorders of the knee joints and their functional consequences;
Explain how the knee impacts motions at the hip and ankle during closed chain activities.
Logan experiences pain when he goes up and down stairs, squats, and kneels. He enjoys going on long mountainous climbs but notices his left knee was painful for several days following the weekend that he hiked up and down the mountains in Yosemite National Park. Today is his first day with a clinician with whom he made an appointment to see if he can get rid of his knee pain. Cole, his clinician, has just taken Logan's history and is about to begin his examination. Cole tells Logan that he has a good indication of what Logan has but wants to perform a few tests before talking over treatment options.
The knee is a complex joint (Figs. 10.1 and 10.2) with three bones (femur, tibia, and patella), two degrees of freedom of motion, and three articulating surfaces: the medial tibiofemoral, lateral tibiofemoral, and patellofemoral articulations, which are enclosed by a common joint capsule. However, not all of its ligaments lie within the capsule.
The anterior view of a right knee of a young adult flexed to about 90°. The anterior capsule is excised and the patella turned down to view the joint.
Medial perspective of a right knee with the femur and patella split in half sagittally.
Functionally, the knee can support the body weight in the erect position without muscle activity; an individual is able to rely on the joint's ligaments to maintain quiet standing. The knee plays a primary role in lowering and elevating body weight during sitting, squatting, and climbing, and it permits rotation of the body when turning on the planted foot as a football receiver does when avoiding a pursuing tackler. In walking and running, the normal knee reduces vertical and lateral ...