Each of the body's joints function uniquely to allow certain parts of the body to do necessary movements. Follow the links below to get a better idea of how these joint structures work.   Knee Hip Shoulder Elbow Foot and Ankle

The Knee

The knee joint is formed by the thighbone, or femur, and the tibia, the larger of the two lower leg bones. The fibula, the smaller of the lower leg bones, fits into a depression of the tibia. The knee joint permits both a hinge-like motion between the upper and lower leg and a slight side-to-side motion. The kneecap, called the patella, is not joined directly to any other of the bones, but rather it is held in place by muscles and ligaments. The quadriceps muscles extend from the hip along the front of the femur to the knee. The hamstring muscles extend from the hip along the back of the femur to the knee. 

The muscles are connected to the bones of the knee by tough, cord-like tissues, called tendons. The quadriceps tendon connects the quadriceps to the patella. The patellar tendon connects the patella to the tibia. Additional strength is provided to the knee joint by the ligaments which connect the bones  from front to back and side to side. The cruciate ligaments (anterior and posterior) are located along the front and back inside surfaces of the knee, while the collateral ligaments (medial and lateral) are located on the outside surfaces of the knee. 

A synovial capsule surrounds the knee joint, contributing to the connection between the femur and the tibia. Synovial fluid, which is secreted into the capsule, nourishes the joint surfaces and reduces friction and stress during joint movement.  Two crescent-shaped pads or discs of tough connective tissue, called menisci, serve to cushion the bony surfaces of the tibia and femur and help to absorb the shock produced by joint movement and weight-bearing.

For more information about the Knee, visit Central States Orthopedic Specialists.

The Hip

The hip joint is a ball-and-socket joint formed by the head of the femur, or thigh bone, and the acetabulum of the pelvis. This union supports weight bearing as well as absorbing the forces created by physical activity, standing, and sitting.

Strong capsular ligaments surround and support the hip joint, and muscles from the lower back, pelvis, and thigh contribute to strength and stability. The head of the femur is covered with a smooth layer of cartilage, which helps to absorb shock and reduce friction during movement, while synovial fluid further cushions the joint and transports essential nutrients to joint structures.

Important differences exist in the size and structure of the hip and pelvis in men and women. A woman's bone structure is slightly less dense than a man's, and the pelvis is smaller, shorter and wider. Additionally, the bony protrusions for muscle attachment are not as sharply defined. 

For more information about the Hip, visit Central States Orthopedic Specialists.

The Shoulder

The shoulder is the only joint in the body that can accomplish a 360-degree rotation, although this level of mobility translates into a lesser degree of stability than other joints. The primary function of the shoulder is to support, or anchor, the different positions of the hand and arm. 

The bony structures of the shoulder include the scapula, humerus, and clavicle, which together create two separate joints -- the glenohumeral joint and the acromioclavicular joint. Some of the muscles and tendons that support the shoulder joint are referred to as the rotator cuff. 

For more information about the Shoulder, visit Central States Orthopedic Specialists.

The Elbow 

The elbow joint connects the bone of the upper arm, the humerus, with the two bones of the lower arm, the radius and the ulna. Within the joint structure are three smaller joints, created by the communication of the three separate bones.

The humerus-ulna joint and the humerus-radius joint contribute to the hinge-like motion of the arm. The radius-ulna joint and the humerus-radius joint permit rotation of the forearm and the palm-up, palm-down positioning of the hand. 

For more information about the Elbow, visit Central States Orthopedic Specialists.

The Foot and Ankle

Structures of the foot comprise a highly integrated group of 26 bones, with numerous muscles, tendons, and ligaments holding the bony structures together in proper alignment and providing support for balance and movement. 

The ankle is formed by the juncture of three bones - the lower ends of the tibia and fibula (the lower leg) and the uppermost bone of the foot, called the talus. The uniquely curved dome of the talus bone permits the hinge-like movement of the foot. 

Beneath the ankle joint are additional tarsal bones, which form the lower portion of the heel and its connection to the metatarsal bones of the foot. The Achilles' tendon joins the heel to the muscles of the calf. The metatarsal bones form a portion of the arch, or instep, of the foot and connect to the phalanges, or toe bones, at the "ball" of the foot. A broad sheath of tendons called the plantar fascia supports and cushions the foot and heel. A thick layer of fatty tissue between the skin and the underside of the foot and ankle provides additional cushioning from the stresses of weight bearing and joint movement. 

For more information about the Foot and Ankle, visit Central States Orthopedic Specialists.