Human Anatomy - Zinoviy Mirchuk, Maryna Mirchuk 2007

Joints of the Limbs

The shoulder joint is formed by the HEAD of the humerus and the glenoid cavity of the scapula. The Joint Capsule is reinforced by Ligaments and Muscles. The tendon of the long head of the biceps brachii passes directly through the articular cavity. In terms of articular surface shape, the shoulder joint is a classic ball-and-socket joint, making it the most mobile in the body. It allows movement around three axes: frontal (flexion and extension), sagittal (abduction and adduction), and vertical (medial and lateral Rotation of the arm along with the forearm and hand).

The elbow joint is a compound joint formed by the articulation of three bones: the humerus, ulna, and radius. It integrates three distinct joints: the humeroulnar joint (between the humerus and the ulna), the humeroradial joint (between the humerus and the radius), and the proximal radioulnar joint (between the radius and the ulna proximally). These joints share a common capsule reinforced by ligaments. The elbow joint permits flexion, extension, pronation (inward rotation of the forearm), and supination (outward rotation of the forearm). These movements occur around a vertical axis, with the ulna maintaining its standard position in the forearm while the radius rotates around it along with the hand.

The radiocarpal joint is the articulation between the radius and the proximal articular surfaces of the scaphoid, lunate, and triquetral bones. This joint allows for the following movements: flexion (palmar flexion), extension (dorsal flexion), adduction, abduction, and circumduction.

The BONES OF THE hand are connected by several joints reinforced by short, strong ligaments: the midcarpal joint (between the proximal and distal rows of Carpal Bones), the carpometacarpal joints (between individual carpal bones and the bases of the Metacarpal bones), and the interphalangeal joints. Together, they enable a wide range of movements, including flexion, extension, and the opposition of the thumb to the other fingers.

The hip joint is formed by the head of the Femur and the acetabulum of the pelvis. The joint capsule encompasses the greater part of the femoral neck and attaches to the pelvic and thigh bones in such a way that a significant portion of the neck lies within the articular cavity. The cavity also contains the ligament of the head of the femur, which transmits Blood Vessels and nerves. The hip joint has a spherical shape and is classified as a multiaxial joint. It allows for a diverse range of movements: flexion, extension, abduction, adduction, and circumduction.

The knee joint is formed by the articular surfaces of the femoral and tibial condyles. Its anterior surface is adjacent to the Patella—the largest sesamoid bone (resembling a sesame seed), embedded within the tendon of the quadriceps femoris Muscle. The patella facilitates the smooth gliding of this muscle's tendon and increases the range of motion in the joint. The articular surfaces of the femur and Tibia are supplemented by intra-articular cartilages known as the medial and lateral menisci. The knee joint is reinforced by ligaments located both inside and outside the joint cavity, which connect with the menisci, joint capsule, condyles, and epicondyles of the femur and tibia.

The knee joint features several synovial bursae, which can accumulate significant amounts of fluid when the knee is injured or diseased. Based on the configuration of its articular surfaces, the knee joint is a typical condylar joint. It permits movement around two axes: flexion and extension along the frontal axis, as well as rotation of the lower leg around a vertical (longitudinal) axis when the knee is bent. The ankle joint is formed by the articular surfaces of both leg bones (tibia and Fibula) and the talus. The distal ends of the tibia and fibula—specifically the medial and lateral malleoli—grip the trochlea of the talus tightly, resembling a wrench or fork. This articulation is secured by a robust ligamentous apparatus. The ankle joint is classified as a hinge (ginglymus) joint. It allows movement around the frontal axis (plantarflexion and dorsiflexion of the FOOT) as well as slight lateral movement when the foot is fully plantarflexed.