Know your feet

The foot and ankle is one of the most complex and yet so flexible creations in the human body. Various bones, muscles, tendons and ligaments of foot work together to provide balance, stability, movement, and propulsion.

This complex anatomy consists of:

• 26 bones
• 33 joints
• Muscles
• Tendons
• Ligaments
• Blood vessels, nerves, and soft tissue

In order to understand conditions that affect the foot and ankle, it’s important to understand the normal anatomy of the foot and ankle.

Ankle

The ankle consists of three bones attached by different ligaments and  its movement is controlled by different muscles and tendons, that connect the foot to the leg. Upper end of ankle joint is consist of lower end of two leg bones tibia (shin bone) and the fibula. Lower end of ankle joint is formed by talus. Thus these three bones form ankle joint which is a synovial joint; fluid containing joint. It allows up and down movement of foot.

The bony protrusions that we can see and feel on the ankle are

• Lateral Malleolus: Is the distal end of the fibula and forms the outer aspect of ankle joint.
• Medial Malleolus: Is the distal end of the tibia and forms inner aspect of ankle joint.

Foot

Distal to ankle joint the arch shaped part of the body is foot. Foot is anatomically divided into three sections called the hind foot, mid foot, and forefoot. It is also divided into two column, medial and lateral. Medial column forms medial arch and lateral column forms lateral arch. Foot also acts as tripod, one pod is heel where both the arches join and the other two is the distal end of two arches at ball of 1^st toe and 5^th toe respectively.

Hind foot

Hind foot is the rear part of foot just below ankle joint. The other term of hind foot is heel. It is formed by two bone talus and calcaneus. The talus bone supports the leg bones (tibia and fibula), forming the ankle joint. The calcaneus (heel bone) is the largest bone of the foot is just below talus forms subtalar joint. Calcaneus and talus connect hind foot with mid foot through cuboid and navicular bone. So hind foot is the connection between leg and mid foot and transfer most of the body weight to ground.

Mid foot

The midfoot is a collection of five small bones called tarsal bone which form the arches of the feet following the principle of ‘Roman Arch’ configuration. Three of these are pyramid shaped called cuneiform bones forms distal row. Among the other two  one is discoid shaped called navicular bone and the other is cuboid shape represents it name. both of these bone form distal row. It connects the forefoot to the hind foot and are attached by different ligaments. The important ligament is spring ligament. The mid foot is responsible for forming the arches of your feet and acts as a shock absorber when walking or running. The mid foot connects to the forefoot at the five tars metatarsal base and form tarsometatarsal joint.

Forefoot

The forefoot consists with five long bones, called metatarsal bones and small bones of each toes named phalanx, connected at the end of each metatarsal bone. There are two phalanxes for great toe and three for other each toes. Phalanges connect to metatarsals at the ball of the foot by metatarsophalangeal joints. At the ball of great toe there are two small round shaped bones named sesamoid bones within the substance of flexor hallucis longus tendon. Sesamoid bones help in weight transfer and movement of great toe.

The first metatarsal bone connected to the big toe is the shortest and thickest of the metatarsals. It transfer most of the body weight through forefoot. This bone is also important for its role in propulsion.

Soft Tissue Anatomy Our feet and ankle bones are held in place and supported by various soft tissues.

• Ligaments: Ligaments are strong rope or band like tissues that connect bones across the joints providing stability and also help to hold tendons in place. There are few important ligaments of foot and ankle which are of our interest because of their involvement in different injury and disease of concern. Deltoid, talo-fibular, calcaneo-fibular and syndesmotic ligament of ankle are associated with ankle sprain. Spring ligament at talonavicular joint related to adult acquired flat foot and Lisfranc’s ligament of mid foot is associated with Lisfranc’s injury. Planter fascia a special type of fascia like ligament spreads from heel to ball of toes and maintains foot arch and acts as spring.
• Tendons: Tendons are rope like tissue extension of muscle that connects muscles to bones to provide support and . The Achilles tendon, also known as the heel cord, is the largest and strongest tendon in the body. It connects calf muscle to heel bone and situated at back of the ankle and wraps around the calcaneus, or heel bone. This tendon can become painful when degenerated, even can get ruptured. Tibialis posterior tendon at medial aspect of ankle and peroneal tendon at lateral aspect of ankle can also get degenerated and cause painful disability. Tibialis posterior tendon is related to adult acquired flat foot deformity.
• Muscles: Muscles are the contractile tissues initiated body movement by pulling different part of bones across joints. There are 20 muscles in the foot and these are classified as intrinsic or extrinsic. The intrinsic muscles are those located in the foot and are responsible for toe movement. The extrinsic muscles are located at lower leg and extend to foot as tendon. The gastrocnemius (calf muscle) is the largest of these and assists with movement of the foot. Muscle strains occur from overuse or it got stretched on sudden forceful activity without proper warm-up.

Other than above these soft tissue structure there are two other important soft tissue structures are there, cartilage and bursa which have their specific role in maintaining smooth functioning of foot.

Cartilage: cartilage is shiny and smooth soft tissue covers the bone surface forming a joint. It allows smooth movement as well as absorb forces. It is pain insensitive. Cartilage can be damaged due to acute trauma or repetitive stress

Bursae: Bursae are small fluid filled sacs that decrease friction between tendons or from bone or skin. Bursae has a special lining called synovial lining similar as joint surface. It secretes a lubricating fluid which helps in lubrication and also provides nutrition to the adjacent tendons. This lining can be inflamed or infected and cause a painful condition, bursitis.

Biomechanics of Foot & Ankle

Biomechanics is a term to describe mechanism which maintains movement of the body and its balance during these movements. Different joints itself has its own range of movements which get in actioned by different muscles across the joints. By acting together and synchronously all the joints of foot and ankle initiate and propagate different movements of our body, walking running, jumping, landing, standing and so on and also maintain balance of the body during these activities.

Ankle joint permits plantar flexion which is moving the foot downward. And dorsiflexion which is moving the foot upwards. These movements are normally accompanied by inversion when sole of foot faces inwards and eversion when sole of foot faces outwards. Eversion and inversion occurs at subtalar joint and different mid foot joints.

The toes allow four different movements, planter flexion, dorsiflexion, adduction and abduction.

Plantar flexion: Bending the toes downwards

Dorsiflexion: Bending the toes upwards

Abduction: Spreading the toes apart. This movement normally accompanies dorsiflexion.

Adduction: Bringing the toes together. This movement normally accompanies plantar flexion.