Bone Growth
When babies grow in their mother’s womb their skeleton is made from cartilage. As they babies grow older, the cartilage develops into bone which is much firmer and tougher than cartilage. This process is called Ossification. This process continues until you’re fully grown. On the ends of our bones there are areas which contain cartilage; these are called growth plates. The cartilage is turned into bone and the bone continues to grow until you are adults.
Effects of Exercise on Bones and Joints
Exercise is critical for strong muscles and bones. Muscle strength declines as people age, but studies report that when people exercise they are stronger and leaner than others in their age group.
Our Body responds to exercise by becoming stronger. This is because mineral content increases within our bones, this makes them harder and stronger. Exercise affects our joints by increasing the thickness of cartilage at the end of our bones. Synovial fluid also increases around our joints, to make the joint stronger and a greater shock absorber.
Joints are complex structures. They are designed to bear weight and move the body. Above the knee is the femur (thigh bone). Below the knee is the tibia (shin bone) and fibula. The kneecap is also called the patella. It rides on top of the lower portion of the femur and the top portion of the tibia. The muscles and ligaments connect these bones and the space between them is cushioned by fluid-filled capsules (synovial) and cartilage. When you exercise, the muscles pull on the bones, strengthening them. The range of motion of a joint represents how far it can be flexed (bent) and extended (stretched).
Joints need to move to stay healthy. If you don’t use your joints for long periods of time, they can stiffen and cause the adjoining tissue to weaken. A moderate exercise program that includes low-impact aerobics and power and strength training has benefits for osteoarthritis people.
Synovial Joints
These are freely movable joints. Most of the joints in the body are of the synovial type. The following are the main characteristics of a synovial joint:
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The ends of the bones are covered with a layer of smooth hyaline cartilage, called articular cartilage in the joint regions. This reduces friction at the point.
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The joint is completely enclosed by a bag-like capsular ligament which holds the joint together and helps to contain the synovial fluid.
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The capsular ligament is lined with a synovial membrane. This membrane secretes synovial fluid into the synovial cavity and acts as a seal, waterproofing the joint. The synovial fluid lubricates the joint.
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In addition to the capsule, the bones are also attached and held together by strong, tough ligaments made of dense connective tissue. These ligaments prevent dislocation during normal movement.
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The articulating surfaces of adjacent bones are reciprocally shaped.
These are the six major types:
Ball-and-Socket Joint
The globular head of one bone articulates with the cup-shaped cavity of another. This joint allows for the most freedom in movement than any other joint. It permits movement in all planes and rotational movement around a central axis. Examples: Hip, Shoulder
Condyloid Joint
The ovoid condyle of one bone fits into the elliptical cavity of another. This joint allows a variety of movements in different planes, but not rotational movement. Examples: Metacarpals to Phalanges, Mandible to Temporal bone
Gliding Joint
The articulating surfaces are flat or nearly curved. This joint allows sliding or back-and-forth motion and twisting movements, however, it does not allow great distance in movement. Examples: Wrist, Ankle, Vertebra
Hinge Joint
The convex surface of one bone fits into the concave surface of another. It permits movement in one plane only. Examples: Elbow, Phalanges
Pivot Joint
The cylindrical surface of one bone rotates within a ring of bone and fibrous tissue of a ligament. This joint permits rotational movement only. Examples: Radius to Ulna, Atlas to Axis
Saddle Joint
In this joint, both bones have articulating concave and convex regions. One bone fits the complementary surface of the other. This permits a variety of movements, particularly in two planes. Examples: Carpal and Metacarpal of the Thumb.
Movement occurring at the Synovial Joints
The Movement occurring at the synovial joints during these activities are:
A penalty in football:
Flexion and Extension: On the Knee Joint (Patella)
Protraction and Retraction: You move your leg forward and backwards (Tibia and Fibula)
A Golf Swing:
Flexion and Extension: You move your arms forward and back, closer and further away from you. The elbow joint. (Patella)
Breast Stroke whilst Swimming:
Flexion and Extension: Moving your arm forward and backward in 90 or more degree angle. The arm and the elbow joint.
Circumduction: Your arms and legs moving the same way.
Protraction and Retraction: Moving your les and arms, forwards and backwards.
