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.
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.
The hand and wrist are complex structures with three types of bones and 27 bones altogether. These are: 8 carpal or wrist bones, 5 metacarpal or “palm” bones, and 14 phalanges or finger and thumb bones. The carpals are round and rotate in a ball-bearing type of motion at the end of the radius bone. This gives your wrist the flexibility to move in any direction.
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. 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.
The knee is the largest joint in the human body and one of the most complex. It allows you to walk and run, execute a variety of different body positions, and change the direction of your body movement. However, the knee also serves as an important focal point for weight-bearing. It is subjected to tremendous forces — approximately 4 times the body’s weight during walking and about 8 times the body’s weight when running. This, combined with the unique structure of the knee joint, makes knee problems the number one reason people seek the attention of an orthopedic specialist. An estimated 4 million people seek treatment for knee injuries and pain each year.
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.
The back is one of the most important structural parts of the human body, allowing us to stand upright and balance on two legs. But it is also subject to many traumatic forces that can, either suddenly or over time, cause what most people simply call “back problems”. Sometimes the problem results in minor aches and pains, sometimes in severe but intermittent pain, and sometimes chronic or permanent disability.
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