Joints How Joints Are Classified According to movability According to the material binding them together How Joints Are Classified Joints may be classified according to how movable they are: fixed, semimovable, or freely movable. They may also be classified according to the material that binds them together. Fixed joints are called fibrous joints (or synarthroses) Semimovable joints are called cartilaginous joints (or amphiarthroses) Freely movable joints are called synovial joints (or diarthroses) Synovial Joints Joint capsule Synovial membrane Joint cavity Articular cartilage Ligament Synovial Joints Every synovial joint contains the following: Joint capsule Synovial membrane Joint cavity Articular cartilage Ligaments Some joints contain bursa Question Most of the joints in the body are: A. fibrous joints. B. synovial joints. C. cartilaginous joints. D. synarthroses. Types of Synovial Joints Pivot joint Hinge joint In a pivot joint, a projection from one bone articulates with a ring-shaped socket of another bone, allowing the bones to rotate, or pivot. A hinge joint allows only back-and-forth movements (flexion and extension), like the hinge of a door. Types of Synovial Joints In a gliding joint, two relatively flat bone surfaces slide over each other; surrounding ligaments limit the amount of movement. They are the least mobile. In a ball-and-socket joint, the ball-shaped head of one bone fits into a cuplike socket of another bone. Ball-and-socket joints offer the widest range of motion of all joints. Gliding joint Ball-and-socket joint Types of Synovial Joints In a saddle joint, surfaces of both bones are shaped like the surface of a saddle: concave in one direction and convex in the other. The bones move back and forth and from side to side (limited). In a condyloid joint, an oval convex surface on one bone fits into a similarly shaped depression on another. They allow flexion and extension, as well as side-to-side movement. Saddle joint Condyloid joint Question Which joint offers the widest range of motion? A. Hinge joint B. Gliding joint C. Condyloid joint D. Ball-and-socket joint Movements of Synovial Joints Depend on the shape of the joint Depend on the involvement of nearby muscles, tendons, and ligaments Shoulder Called the humeroscapular joint (denoting the articulation of the humerus with the scapula) or the glenohumeral joint (denoting the articulation of the head of the humerus with the glenoid cavity of the scapula), the shoulder is a ball-and-socket joint. It has the greatest range of motion of any joint. The shoulder is the most likely joint to dislocate. Elbow The elbow is a hinge joint that consists of two articulations: one between the humerus and the ulna (the humeroulnar joint), and the second between the humerus and the head of the radius (the humeroradial joint). A single joint capsule encases both articulations. Knee Condyles Knee Called the tibiofemoral joint, the knee is the largest and most complex joint in the body. The condyles of the femur perch on the flat upper surface of the tibia. Two slightly concave pieces of cartilage (the medial meniscus and the lateral meniscus) cradle the condyles and absorb shock. Hip Ligaments Hip The hip is a ball-and-socket joint (like the shoulder). It is more stable than the shoulder, mainly because the hip socket is deeper than the socket of the shoulder joint. Question Which joint is most likely to be dislocated? A. Shoulder B. Hip C. Knee D. Elbow