achilles tendon injury -

Before looking at the achilles tendon it is beneficial to understand the mechanics of the ankle joint itself.

In all human beings whether a runner or not the ankle joint is essentially the same! The ankle joint is formed where the bones of the lower leg, the tibia and the fibula, connect above the anklebone, called the talus. The tibia is the main bone of the lower leg. The fibula is the small, thin bone along the outer edge of the tibia.

The ankle joint is a hinge that allows the foot to move up (dorsiflexion) and down (plantarflexion). The ankle is a synovial joint, meaning it is enclosed in a joint capsule that contains a lubricant called synovial fluid.

Strong ligaments surround and support the ankle joint. The ligament that crosses just above the front of the ankle and connects the tibia to the fibula is called the anterior inferior tibiofibular ligament (AITFL). The anterior talofibular ligament (ATFL) supports the outer edge of the ankle. The ATFL goes from the tip of the fibula and angles forward to connect with the talus.

The talus rests on the the heelbone (the calcaneus). The joint formed between these two bones is called the subtalar joint. The calcaneus extends backward below the ankle, forming a shelf on which the talus rests.

Two small bony bumps, called tuberosities, project from the back of the talus, one on the inside (medial) edge and one on the outer (lateral) edge.

achilles tendon injury -

The achilles tendon joins three muscles: the two heads of the gastrocnemius and the soleus. The gastrocnemius heads arise from the posterior portions of the femoral condyles (back of the thigh bone). The soleus arises from the posterior aspect of the tibia and fibula (the two bones in the lower leg).

The gastrocnemius is a muscle that crosses three joints: the knee, the ankle, and the sub-talar joint (major joint in the foot). The functioning of these joints and influence of other muscles on these joints has a significant effect on the tension that occurs within the achilles tendon. As an example tight hamstrings impact the functioning of the ankle joint, the sub-talar joint, and increase tension in the achilles tendon. The soleus muscle does not cross the knee and is a bi-articular muscle (affects the movement of two joints).

The bulk of the achilles tendon inserts into the upper back  third of the calcaneus (heel bone). Some fibres run further down and insert into the bottom of the heel bone.