Joints, Ligaments and Tendons
Joints: Where Movement Happens
A joint is any point where two or more bones meet. The type of joint determines precisely which movements are possible at that site. For GCSE Physical Education, you need to know four types of synovial joint — pivot, hinge, condyloid and ball-and-socket — and for each type: where it is in the body, which movements it permits, and how those movements appear in sport.
The Four Synovial Joint Types
All four joint types share the same basic synovial structure: a fluid-filled cavity enclosed in a fibrous capsule, with cartilage covering the bone surfaces to reduce friction. What differs is the shape of the articulating surfaces, which determines the range of permitted movement.
The pivot joint permits rotation only. The two pivot joints in the body are the atlanto-axial joint (between the atlas and axis — the top two cervical vertebrae), which allows you to rotate your head side-to-side as in a swimmer checking for a lane marker, and the proximal radioulnar joint in the forearm, which allows pronation and supination of the palm — movements used in badminton smashes and cricket spin bowling.
The hinge joint works like a door hinge, permitting flexion and extension in a single plane. The three hinge joints relevant to sport are the elbow (humerus and ulna), the knee (femur and tibia) and the ankle (tibia/fibula and talus). The knee produces the powerful extension needed to drive off the ground in sprinting; the ankle hinge is the axis for plantar-flexion (pointing the foot, as when a gymnast points their toes) and dorsi-flexion (lifting the toes, as when pulling the foot up at the end of each stride).
The condyloid joint (sometimes called an ellipsoidal joint) allows movement in two planes: flexion and extension plus abduction and adduction, giving circumduction but not rotation. The primary example is the wrist (radius and carpals). The condyloid joint at the base of each finger (metacarpophalangeal joints) also belongs to this category. In sport, the wrist condyloid joint allows the flicking motion used in a basketball free throw and the angling of the wrist in catching a cricket ball.
The four synovial joint types: pivot (atlanto-axial, radioulnar — rotation only), hinge (elbow, knee, ankle — flexion/extension), condyloid (wrist — flexion, extension, abduction, adduction, circumduction), ball-and-socket (hip, shoulder — all movements including rotation and circumduction).
The ball-and-socket joint is the most mobile joint in the body, allowing movement in all planes. The shoulder (humerus head into the glenoid cavity of the scapula) and the hip (femur head into the acetabulum of the pelvis) are ball-and-socket joints. The shoulder allows the greatest range, including the full-arm circumduction used in freestyle swimming and the overarm throwing action in cricket. The hip allows the wide abduction needed in a gymnastics box split and the powerful extension that drives each running stride.
Movements at Joints
You need to know eight specific movement terms and apply them to sporting actions. Flexion is decreasing the angle at a joint — bending the elbow to bring the hand towards the shoulder. Extension is increasing the angle — straightening the elbow when pushing in a press-up. Abduction is moving a limb away from the midline of the body — raising the arm sideways in a jumping jack. Adduction is moving towards the midline — lowering the arm back to the side. Rotation is turning a bone around its own long axis — the internal rotation of the humerus in a forehand tennis stroke. Circumduction is a combined cone-shaped movement combining flexion, extension, abduction and adduction — the arm action of a windmill bowling in cricket. Plantar-flexion is pointing the foot downward at the ankle — pushing off the floor in a sprint start. Dorsi-flexion is pulling the foot upward at the ankle — the heel-strike phase of running.
Students often confuse condyloid and ball-and-socket joints because both allow circumduction. The key difference is rotation: a ball-and-socket joint allows rotation of the limb around its long axis; a condyloid joint does not. Try rotating your wrist like a screwdriver — that movement actually comes from the radioulnar pivot joint, not the wrist condyloid joint. The wrist itself only flexes, extends, abducts and adducts. The shoulder, by contrast, can rotate the humerus independently of any other movement — as when winding up a throw. In exam questions, if asked whether the wrist allows rotation, the answer is no.
Ligaments and Tendons
Ligaments connect bone to bone. They are made of dense, fibrous connective tissue that is flexible enough to allow normal joint movement but strong enough to prevent the joint from dislocating or moving beyond its safe range. The anterior cruciate ligament (ACL) of the knee, for example, prevents the tibia from sliding forward on the femur — it is commonly ruptured in football and skiing when the knee twists under load.
Tendons connect muscle to bone. They transmit the contractile force generated by the muscle belly to the bone, causing the bone to move at the joint. Tendons are inelastic — they do not stretch under load the way muscles do. The Achilles tendon connects the gastrocnemius and soleus to the calcaneus (heel bone) and is the largest tendon in the body, transmitting the enormous forces generated during jumping and sprinting. Tendons can become inflamed (tendinopathy) from repetitive overuse.
Ligaments connect bone to bone, stabilising joints. Tendons connect muscle to bone, transmitting the pull of muscle to create movement. Ligaments are most at risk in contact and twisting sports (e.g. ACL in football); tendons are most at risk in repetitive overuse activities (e.g. Achilles tendinopathy in distance running).
Ligaments have a relatively poor blood supply compared to muscles. When a ligament is sprained — stretched or partially torn — the limited blood flow means the repair process is slow. Partial tears may take 6–12 weeks to heal; complete tears (rupture) of major ligaments such as the ACL often require surgical reconstruction followed by months of rehabilitation. This is why protecting ligaments through correct technique, appropriate footwear and gradual progressive overload is a key principle of sports injury prevention. Good proprioceptive training (balance work) also strengthens the neural reflexes that prevent joints from entering unsafe ranges in the first place.