Read up on the ankle and how it works. This joint is actually two joints that allow the foot to move up and down and side to side.
Ankle Anatomy: Muscles and Ligaments
Frontiers An Identical Twin Study on Human Achilles Tendon Adaptation: Regular Recreational Exercise at Comparatively Low Intensities Can Increase Tendon Stiffness
Ankle and foot support critical for maintaining balance – Human Kinetics
Human Kinetics Sport Science & Sports Medicine - Synovial (or diarthrodial) joints are subclassified into six different types according to the movements allowed and the structure of the joint. Gliding joints are
Ankle: Anatomy & How It Works
The Basics of Ankle Anatomy and Foot Anatomy
Tibialis Posterior: Pain On The Inside Of The Ankle
Anatomy and Physiology: A Peek at Lower Leg and Foot Pathologies
Ankle and foot support critical for maintaining balance – Human Kinetics
Muscular Function & Anatomy of the Lower Leg & Foot - Lesson
Ankle Sprains – The Nicholas Institute of Sports Medicine and Athletic Trauma
Sports Medicine
Foot Ankle Archives - ADVANZ HEALTH