The ankle is the springboard for human movement. Ever since the day long ago when hominids first made the leap from the trees and stood upright on the plains to get a better view of their surroundings, we have relied on the foot and the ankle to apply force to the ground to propel us into movement.
Take off your shoes and socks and have a look at your ankle and foot. Put a mirror on the floor if you want to see more of the bottom of your foot.
The ankle has evolved into a complex joint with two major functions during the time the foot is in contact with the ground.
First, your foot needs to be a flexible shock-absorber. The impact forces that are generated by a 60kg or 120lb person running at 10km an hour are huge, and the foot is designed to be a pliable, flexible structure when the heel hits the ground. This is why there are so many bones, tendons, and ligaments in the foot.
The main shock-absorbing bones are at the back of the foot under the ankle, are short and chunky, and surrounded by bands of ligaments. This structure is great for absorbing and dissipating the excessive forces generated as your body accelerates towards the ground with every step you take.
The large and chunky bones are like life rafts moored together by strong hawsers called ligaments. Feel the large bones around the base of the ankle.
These bones have wonderful names, such as the “talus”, the “navicular”, the “calcaneus” and the “cuboid” bones. The inside ligaments which guard these bones start on the shin bone (the tibia) and then fan out to link the navicular, the talus, and the calcaneus. On the outside, the ankle is guarded by the lateral ligament which spreads out from the outside ankle bone (“lateral malleolus”) to moor the talus and the calcaneus.
The top of the ankle has the “tibiofibular ligament” which, as you can tell from its name, links the lower leg bones — the tibia and the fibular. The least protected area of this part of the ankle is the front, which is why many ankle sprains occur towards the front of the sides of the ankle joint.
The ankle is also reinforced by the long tendons of the shin muscles which link the lower leg to the foot. You can see these by moving your foot and looking for the tendons standing out from the bones. These tendons are tied down by a girdle of ligament around the ankle so they don’t spring out when you move.
While all this is happening, the front of the foot is loose and relaxed, lessening the impact being transmitted up your leg and into your lower back.
Second, the foot is a rigid platform for transmitting the force generated by the muscles of the body to the ground to produce maximum propulsive force.
Moments after your heel hits the ground, muscles inside the foot contract to pull the bones together to create a rigid platform.
The longer bones in the front of the foot are called “metatarsals”, and these end in the “phalanges”, or the toes as you know them. These longer bones act as levers to magnify the forces as they pass through the foot to the toes, and then into the ground.
The foot also changes shape, and becomes more curved in the propulsion phase of walking or running. You can see this happening if you put a towel on the floor and use your toes to try to pull the towel backward.
This curved shape makes the foot good at applying force in any direction, so you can move easily to the sides and to the back, as well as to the front.
What is a sprain, and how is it different from a strain? A sprain is a term used to describe damage to a muscle or tendon. A strain refers to damage done to a ligament.
The most common injuries to the ankles are an inversion strain and an eversion strain.
An inversion strain happens when the sole of the foot turns inwards, and the ankle rolls outwards. The outer (lateral) parts of the foot suffer the most damage, and the amount of damage depends on the amount and direction of the forces applied to the ankle. The lateral ligaments are most damaged, although there may be associated damage to the bones of the ankle or foot.
These sprains occur when you suddenly change direction or twist when your foot is firmly planted on the ground, or step on uneven ground.
An eversion strain happens when the sole of the foot is forced outwards, and the ankle rolls inwards. The inner (medial) parts of the ankle suffer the most damage.
These sprains occur when you step on uneven ground or twist when your foot is firmly planted on the ground.
These strains are more often associated with fracturing or cracking of the bones of the ankle and the breaking of the ligament that binds the bones of the lower leg.
Less common is a dorsiflexion strain, where you land flat-footed and the impact forces the talus between the bones of the lower leg. The ligament that binds these bones is strained or snapped.
Least common is a plantarflexion strain, which occurs when you catch the front of your foot when jumping over something when running.
A moderate strain will strain only the front of the ankle, but a severe strain may cause a crack in the back of the tibia, the large bone in the lower leg.
Ankle First Aid
All ankle strains should be treated seriously and we recommend that after applying first aid, you get along to a sports doctor immediately.
The initial pain and damage to the softer tissues can often disguise a more serious injury.
Why you need to buy the right types of shoes for your activity:
- Running shoes are designed for a strong heel impact, to absorb the impact of your heel hitting the ground, and to allow for a full heel-to-toe ankle movement.
- Aerobics shoes are designed for a midfoot strike, so they are less flexible and have less shock absorption.
- Cross-trainer shoes are designed for maximum stability of the foot.
Wearing the wrong shoe for the wrong activity can interfere with the efficient movement and reaction of the foot, and may lead to chronic ankle, knee, hip, and lower back injuries.