The ankle joint is actually a compound joint with complex motion and rotation, so a brief review of the functional anatomy of the ankle joint is essential before studying its reading methods. Familiarity with the normal functional anatomy of the ankle joint is necessary to study the mechanics of ankle injuries, to examine and identify ligamentous injuries, joint instability, and clinical management. The primary functions of the ankle joint are dorsiflexion and plantarflexion. Under normal physiologic conditions, the ankle joint movement constitutes a “compound” movement with the subtalar and middle tarsal joints of the foot. When the normal ankle joint is in a fixed position, the talus is firmly fixed in the tenon of the ankle joint. Although the joint is more loose in plantarflexion and tense in dorsiflexion, it maintains the relative stability of the joint in any fixed position, and cannot be internally rotated, externally rotated, internally rolled over, externally rolled over, or other activities. When the ankle is in motion, the ankle itself is not moving in a single direction, but in a “compound” motion. The ankle joint from plantarflexion to dorsiflexion activity process, at the same time, produce the talus from internal rotation to external rotation, from inversion to eversion; tibia is in the talus trolley surface relative to the external rotation to internal rotation; fibula from the anterior to posterior and upward from the bottom, and external rotation; the distance between the ankle gradually increased and a series of activities. The ankle joint moves from dorsiflexion to plantarflexion in the opposite direction. The reasons for the above activities are determined by the special anatomical structure of the ankle joint itself, which are explained as follows: I. Why does the talus turn inward and outward when the ankle joint is flexed and extended? The talus trolley surface is a spiral articular surface with an upward curvature. The talar talus slide is high medially and low laterally anteriorly, horizontal in the center, and high laterally and low medially posteriorly. With the center X-ray beam from anterior to posterior through four different angles to tangent talus articular surface for X-ray photographs clearly see the talus talus surface from front to back is from the outside of the lower tilt gradually changed to the inside of the lower tilt, the front and the back of the intersection of the angle of inclination of 6 ° ~ 10 ° This is the talus talus surface of the helical slope, so talus in the mortise and tenon activities, the talus is inevitably to occur inversion and eversion and rotational activities. Second, why the ankle joint flexion and extension activities at the same time produce talus internal and external rotation? In addition to the above reasons, it can be seen that the medial and lateral articular surfaces of the talus body are two curved surfaces with the same direction. The medial articular surface is a concave half-moon shaped surface, and the lateral articular surface is a convex surface. The curved shape of both articular surfaces protrudes to the lateral side, which determines that the talus will rotate externally from plantarflexion to dorsiflexion and internally from dorsiflexion to plantarflexion when it moves within the mortise and tenon. Why does the inter-ankle distance increase when the ankle joint is flexed and extended? The talus trolley surface is a wedge-shaped body, wide in front and narrow in the back, with a difference of 5-10mm, and the anterior/posterior ratio is about 3:2. When the foot is dorsiflexed, the wider anterior part of the trolley is embedded in the mortise and tenon, which results in the distance between the two ankles increasing, the joint ligament being tensed, and the joint being stabilized. When the foot is dorsiflexed, the wider anterior part of the carriage is embedded in the mortise, resulting in an increased distance between the two ankles, joint ligament tension and joint stabilization. Why is the fibula active during ankle flexion and extension activities? In normal people, when the ankle joint is flexed and extended (the calf is fixed), the fibula moves about 1cm backward when the foot is dorsiflexed and 0.5-1cm upward and rotates outward, which is also determined by the anatomical structure of the ankle joint. Familiarity with the above functional anatomy is the basis for studying the mechanism of ankle trauma and fracture anatomy. From the ankle joint orthopantomograph, the joint space is inverted “U” shape, uniform and equal width, about 0.5cm, and the inner ankle space is clear. If the inverted “U”-shaped joint space is unequally wide in one part, it means that the ligament or joint capsule here has contracture; if the inner ankle space is not clear or narrow, it means that the ankle joint is inverted deformity, and the soft tissues here have contracture. If the inverted “U” shaped joint space is all blurred, it may be the early stage of rheumatoid arthritis. If the inverted “U” shaped joint space is completely narrowed, it may be the advanced stage of rheumatoid arthritis, and the joint capsule is completely contracted. When the ankle joint is maximally plantarflexed, the articular surface of distal tibia is slightly tilted inward and downward, and slightly tilted outward and downward when it is maximally dorsiflexed. This is because the articular surface of distal tibia, like the talar talar surface, is an articular surface with helical slope, and when the ankle joint inversion and eversion injury causes compression and fracture of distal tibia articular surface, the normal relationship will be destroyed and the inversion and eversion deformity of ankle will occur or the destruction of the normal articular surface will lead to osteoarthritis and osteocarcinoma. This disruption can lead to osteoarthritis (a disruption of the internal force balance of the ankle joint). Regardless of the presence of osteomalacia or osteoid formation in a certain part of the ankle joint, if that part is the attachment area of a certain soft tissue (generally referring to muscles, ligaments, joint capsule), it means that the soft tissue has been in a state of tension contracture for a long time, and if such a part is not in the attachment area of the soft tissue, but is in a certain part of the articulating surface (generally in the edge of the joint), it means that the pressure here is very high for a long period of time.