*1.2.1. Ankle*

The ankle is the only anatomical area where the vertical forces are transmitted to the horizontal support system, in this case the foot. The ankle includes the tibiofibular and the subtalar joints. The tibiofibular joint allows the movements of dorsiflexion and plantar flexion or extension in the sagittal plane. The lateral movement of the foot (or eversion) around the anterior-posterior and the medial movement (or inversion) are made in the subtalar joint in the frontal plane. Adduction and abduction movements occur around the vertical axis and the transverse plane. The combination of the movements of the tarsus with those of the ankle allows complex movements, such as: (1) supination, or inversion of the ankle with adduction of the foot and plantar flexion, and (2) pronation, or ankle eversion with abduction of the foot and dorsiflexion*.* 

### *1.2.2. Knee*

The knee is the binding site of two long bones, femur and tibia, which are the major body segments. Small range of motion produces significant changes in the foot or in the body.

The knee joint is very complex, bicondylar, characterized by a very wide range of motion in the sagittal plane and small arcs of motion in the coronal and transverse planes. During the movement of the knee in the sagittal plane, the tibia slides around the distal end of the femur so that the mediolateral axis of rotation displaces with movement.

The patella is the largest sesamoid bone in the human body. It modifies the thrust angle of the quadriceps femoris, affecting the production of muscle force components, so that the rotational component is greater (Nordin & Frankel, 2004).

During support, the knee is essential for the stability of the leg. During swinging, the flexibility of the knee is the main factor that determines the progress of the leg. The number of bicondylar muscles involved in controlling the knee indicates a great functional coordination with the hip and ankle.

The movement in the sagittal plane is used for progression through the support and during swing. During the phase of non support, the knee makes use of a range of movement widest than that of the any other joint. The rotation in the transverse plane accommodates changes in alignment when the body oscillates back and forth of the supporting leg. In walking, when the knee extends, the leg rotates externally; when the knee is flexed, the leg rotates internally. In jogging, the knee is flexed at the beginning of the stance phase while the leg is externally rotated (Novacheck 1998).

The movement in the coronal plane facilitates vertical balance on the leg, particularly during leg stance. In each cycle the knee moves into abduction and adduction. In support phase, the movement is of abduction. During oscillation, the knee returns to a more neutral position in adduction. In the transverse plane of a position of maximum external rotation at the end of the stance phase, the lower limb starts an internal rotation in the take-off of the leg and continues during the oscillation and the load response (initial part of the support phase).
