The knee joint is a synovial condylar joint formed by the interaction between the femur, tibia, and patella. This joint is essential for lower limb function, allowing mainly flexion and extension movements, with a limited degree of internal and external rotation. Joint stability is ensured by a complex ligamentous system, including the medial and lateral collateral ligaments, the anterior and posterior cruciate ligaments, and the joint capsule. The meniscal compartment, consisting of two fibrocartilaginous menisci (medial and lateral), plays a key role in shock absorption and load distribution. The articular surface is covered with hyaline cartilage, which facilitates smooth movement and reduces friction between the bone surfaces. The joint is also surrounded by a series of tendons and muscles that contribute to its mobility and functional stability.

The elbow joint is a synovial hinge joint formed by the interaction between the humerus, radius, and ulna. It primarily allows flexion and extension of the forearm, as well as pronation and supination movements through the associated proximal radioulnar joint. The stability of the elbow is ensured by a complex ligamentous system, including the ulnar (medial) collateral ligament, the radial (lateral) collateral ligament, and the annular ligament of the radius, which stabilizes the radial head during rotation. The joint capsule, rich in synovial fluid, facilitates movement and nourishes the articular surfaces. The articular surfaces are covered with hyaline cartilage, which reduces friction between the bones during motion. Periarticular muscles and tendons contribute to the stability and function of the elbow joint, allowing a wide range of fine and precise movements of the upper limb.

The ankle joint, or talocrural joint, is a synovial hinge joint that connects the tibia and fibula with the talus. It primarily allows dorsiflexion and plantarflexion movements of the foot. Joint stability is ensured by a complex network of ligaments, including the medial (deltoid) collateral ligament and the lateral collateral ligament, which is composed of the anterior talofibular, calcaneofibular, and posterior talofibular ligaments. The joint capsule, containing synovial fluid, lubricates and nourishes the articular surfaces, which are covered with hyaline cartilage to reduce friction during movement. The ankle joint is supported by tendons and muscles that contribute to the mobility and stability of the foot, allowing functional adaptation during walking, running, and balance maintenance.