Anatomy: Elbow, Foot, Hand, Hip, Knee, Shoulder

The Elbow
The elbow joint is made up of three bones: the humerus (upper arm bone), radius and ulna (forearm bones). Together, these three bones form a joint that both acts as a hinge and a pivot, allowing a person to bend, extend and rotate the arm. The elbow connects the end of the humerus to the forearm bones by way of ligaments, tendons and muscles. The joint surface of the elbow is covered by articular cartilage that protects and cushions the joint.

The Foot
The 26 bones in each foot take an incredible pounding on a daily basis — walking, running and bearing stressful loads. This is due to the foot’s unique ability to provide stability and act as a shock absorber.

The foot is divided into three sections — the forefoot, mid foot and rear foot. The fore foot is composed of five metatarsal bones and the 14 phalanges that make up the toes. The mid foot includes five tarsal bones that form the arch of the foot. The hind foot consists of the calcaneus (heel bone) and the talus bone, which forms the pivot of the ankle. These bones are supported by a network of muscles, ligaments and tendons, holding the bones in place and allowing for a variety of movement.  

 The Achilles tendon extends from the calf muscle to the heel and facilitates lifting the heel up. The plantar fascia is a band of tendon-like tissue that runs along the bottom of the foot, from the heel to the ball of the foot. It supports the arch. A thick layer of fatty tissue covers the plantar fascia to absorb the pressure and strain of weight-bearing activities.

The Hand
The hand is made up of many small bones, muscles and ligaments. There are three major types of bones in the hand, the phalanges, metacarpal and carpal. The phalanges are 14 bones that comprise the fingers of each hand. Each finger has three phalanges and the thumb has two. Metacarpal bones form the middle section of the hand. Each hand has five metacarpal bones. Carpal bones create the wrist. These eight bones are connected to the arm bones (ulnar bone and radius bone). Tendons sheath the bones of the hand and finger. Ligaments help hold the fingers’ joints together. Muscles allow the movement of the bones in the hand.

The Hip
The hip is the largest ball-and-socket joint in the body. The head of the femur (thighbone) is shaped like a ball. It fits tightly into the cup-like socket of the thighbone (acetabulum). The surface of the head of the femur and the inside of the acetabulum are covered by articular cartilage that allows the surfaces to glide smoothly over one another. The hip joint is held together by muscles, tendons and ligaments, to help support up to three times a person’s body weight. The hip joint is more stable than the shoulder joint, but does allow for as much motion.

The Knee
The knee is the largest joint in the body. This hinge joint provides stable support for the body and allows the legs to bend and straighten. It is made up of the tibia (shinbone), the femur (thighbone) and patella (kneecap). The lower end of the femur rotates on the upper end of the tibia and is protected in front by the patella, which slides along a groove on the end of the femur.

The knee is kept stable by ligaments and tendons. The collateral ligaments run along the sides of the knees provide stability when the knee moves from side to side. Two large ligaments in the center of the knee, the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) control the front to back motion of the knee joint.

Meniscus cartilage is a pad of cartilage that acts as a shock absorber to cushion the joint and aids in stabilizing the knee. Articular cartilage covers the ends of the bones that form the joint. This allows the surfaces of the knee glide over each other without damaging the surface.

The Shoulder
The shoulder allows the greatest range of motion of any joint in the body. This complex joint allows the shoulder to move forward and backward, and allows the arm to rotate in a circular motion and move up and out away from the body.

The shoulder is composed of the clavicle (collarbone), scapula (shoulder blade) and humerus (upper arm bone). The roof of the shoulder is formed the acromion. The shoulder actually has two joints to facilitate its movement.

The acromioclavicular (AC) joint is located between the acromion and clavicle. The glenohumeral joint, or shoulder joint, is a ball-and-socket joint where the top of the humerus (the ball) fits into the glenoid cavity of the scapula (the socket). Muscles, tendons, and ligaments hold these bones together. Articular cartilage covers the surface of the shoulder joint, allowing the bones to glide smoothly and protects and cushions the joints.