Synovial joints are where two bones meet. The space between the bones is referred to as a joint cavity, consisting of ligaments connecting bones to bone. Tendons, connecting muscles to bones also cross the joints. Spongy pads, known as cartilage, cushion the joint while synovial fluid keeps the joints lubricated. Exercise movements targeting specific muscle groups involve synovial joint movement through a full range of motion.
Ball and Socket Joints
Ball and socket joints are where the round head of a long bone inserts into a capsule of an irregular bone. Locations include the shoulder and hips joints, the most movable joints. Movements occur in more than one plane and include flexion, or bending, extension, or straightening and inward and outward rotation. Additional movements, such as adduction and abduction, involve moving your arms and legs away from and towards your midline. Exercises for your chest, back, shoulders, buttocks and inner and outer thighs involve movement in the ball and socket joints.
Hinge Joints
The hinge joints in your elbows and knees allow movement resembling a door hinge. Movements include elbow and knee flexion, or bending, and extension, or straightening. The tight structure of the joints prevent excessive extension, or hyperextension, which can lead to injury. Exercises such as biceps curls, triceps extensions, leg curls and leg extensions involve the hinge joints. These are isolation exercises, working only one muscle group at a time.
Gliding Joints
Gliding joints lie between bones with flat surfaces, allowing one bone to slide, or glide across another allowing limited joint movement. Your wrists and ankles are gliding joints. The joint movements include flexion and extension of your hands and feet. While there is some lateral movement, excessive lateral movements can lead to joint sprains. Forearm curls and calf lifts are common exercises involving gliding joint movement.
Pivot Joints
Pivot joints rotate one bone around another. The bones in your forearm connect to the upper arm at the elbow joint, which is a pivot joint. Another pivot joint is where your head inserts into your neck. There is limited rotation in these joints. The pivot joints in your elbows allow your hands to move from a palm down to a palm up position that assists in many dumbbell exercises for your shoulders and biceps. Rotation in your neck allows side to side movements of your head.
