Ankle - Anatomy and Imaging

The ankle is the joint between the leg and foot. It is like a hinge but allows rotation as well. 
 
Bones
It is composed of three bones (see images below):
  • tibia
  • fibula
  • talus. 
Capsule and cartilage
The joint is protected by a fibrous membrane called a joint capsule and filled with synovial fluid. 

Like most joints in the human body, the ankle is covered by hyaline cartilage. 
  • This smooth white surface allow joint movement without friction and adds cushioning. 
  • There are no nerves to detect pain in cartilage but the underlying bone and adjacent tissues have many. 
  • Cartilage also has a poor blood supply and doesn't heal well.
  • Cartilage is the "gap" between bones on X-rays (see X-ray below).
Ligaments
Ligaments are soft tissues that hold bones together (see X-ray, MRI and models below).

Ankle ligaments are divided into "high" and "low".

"High" ankle ligaments are also known as the syndesmotic ligaments (AITFL and PITFL). 
  • They hold the two bones of the leg (tibia and fibula) together above the ankle. 
  • This connection is called the syndesmosis. 
  • It allows a small amount of movement between the leg bones during activities.
"Low" ankle ligaments allow ankle movement but still hold the ankle stable.
The important ones are:
  • Deltoid ligament - inside (medial) ankle.
  • Anterior talo-fibular ligament (ATFL) - outside (lateral) ankle.
  • Calcaneo-fibular ligament (CFL) - outside (lateral) ankle.
Tendons
Tendons connect muscles to bones and make joints move (see X-ray, MRI and models below).

The peroneal tendons run down the outside of the leg and ankle to connect with the foot. 
  • Peroneus brevis.
  • Peroneus longus.
  • They both act to keep the ankle and foot stable on uneven ground.
There are other important tendons passing down from the leg to the foot across the ankle.
  • Tibialis anterior.
  • Toe flexor and extensor tendons.
  • Achilles tendon.
  • Tibialis posterior.
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