The ankle is formed by the talocrural joint (crural = leg). It consists of the articulations between the talus bone of the foot and the distal ends of the tibia and fibula of the leg. The superior aspect of the talus bone is square-shaped and has three areas of articulation. The top of the talus articulates with the inferior tibia. This is the portion of the ankle joint that carries the body weight between the leg and foot. The sides of the talus are firmly held in position by the articulations...

Intervertebral disc herniation refers to the displacement of the nucleus pulposus (the gel-like inner core of the disc) through a tear or weakened area in the annulus fibrosus (the outer fibrous ring). The displaced disc material extends beyond the normal boundaries of the disc space and may compress or irritate nearby spinal nerve roots or, less commonly, the spinal cord.Etiology and Risk FactorsHerniation commonly results from degeneration, in which aging reduces disc hydration and...

The thigh's motion is primarily governed by muscles originating in the pelvic girdle and inserted into the femur. One crucial muscle, the iliopsoas, is a combination of the psoas major and the iliacus muscles, sharing a common insertion point on the lesser trochanter of the femur.
Three other significant muscles are the gluteus maximus, gluteus medius, and gluteus minimus. The gluteus maximus originates from the posterior surface of the ilium, sacrum, and coccyx, and the thoracolumbar fascia...

The femur is the body's longest and strongest bone spanning the thigh region. Its head articulates with the acetabulum of the hip bone to form the hip joint. A minor indentation on the medial side of the femoral head, called the fovea capitis, serves as the site of attachment for the ligament of the head of the femur. This weak ligament spans the femur and acetabulum and supports the hip joint. The narrowed region below the head is the neck of the femur. The inclination angle between the neck...

The knee joint is the most complicated joint in the body. It consists of three articulations– two tibiofemoral and one patellofemoral. As is characteristic of synovial joints, the knee joint has a thin articular capsule that partially surrounds this joint cavity. Additionally, several ligaments, muscles, and cartilaginous structures support the movement of the knee.
A total of seven ligaments support the knee joint. The patellar ligament, which is also attached to the quadriceps femoris group...

Functional Classification of Joints
The functional classification of joints is determined by the amount of mobility between the adjacent bones. Joints are functionally classified as a synarthrosis or immobile joint, an amphiarthrosis or slightly moveable joint, or as a diarthrosis, a freely moveable joint. Fibrous and cartilaginous joints can be functionally classified as either synarthroses  or amphiarthroses, whereas all synovial joints are classified as diarthroses.
Synarthrosis
An immobile...