L9: The Leg and Foot Flashcards
Describe the bones of the foot.
The foot is like the hand as it is made of numerous small bones and synovial joints. We have tarsal bones instead of the carpal bones and metatarsals instead of metacarpals. We also have phalanges in the foot/ the big toe has 2 phalanges, like the thumb, and toes 2-5 have 3 phalanges.
The Tarsal bones include the Talus (ankle bone) and the calcaneus (heel bone) distally. Next is the navicular medially and the cuboid bone laterally. Proximal to this, from medial to lateral is the medial cuneiform bone, intermediate cuneiform bone and the lateral cuneiform bone. The cuboid bone extends onto this row also. These bones make up the tarsal.
Distal to the tarsals are the metatarsal and then the phalanges.
Name the landmarks of the tibia and its articulation with the foot.
The tibia is triangular in shape. Anteriorly we see the tibial tuberosity, a site of attachment for the quadriceps muscle. There are also flat tibial plateaus, in which the menisci and the femur attach. The sole line on the posterior tibia are a site of attachment for the soleus muscle.
On the distal tibia we see the medial malleolus and the lateral malleolus on the distal fibula. These are projections at the end of the bone.
The tibia and fibula articulate with the foot at the ankle mortise (a deep socket formed by the tibia and fibula fro the atlas to sit in). The tibia and fibula attach at the malleoli to the Talus bone of the foot. This is the Talocrural joint - a synovial joint made of the fibula, tibia and the talus.
What movements are possible at the ankle joint?
- Flexion (Plantarflextion)
- Extension (Dorsiflexion)
- Inversion (brining the sole inwards)
- Eversion (bringing the sole outwards)
These do not happen at the ankle joint but at the subtalar joint. This lies between the talus and the calcaneum joint.
How is stability at the ankle joint achieved?
There is very good stability at the ankle joint because of:
- Deep ankle mortise and so good congruency - The very strong ligaments
Lateral ligament - More commonly injured than the medial complex. There are 3 lateral ligaments that help to ensure stability.
Medial ligaments There are more ligaments on the medial ligament complex - often referred to as the deltoid ligament. There are many parts to the deltoid ligaments. The medial ligament is attached to the medial malleolus and fans out to attach to the talus, navicular and calcaneus.
What movements are possible at the toes?
- Flexion and extension at the MTPJs, PIPJs, DIPJs and the IPJ of the big toe
- There is limited abduction and adduction at the MTPJs
These are brought about by intrinsic and extrinsic muscles of the foot
How is stability of the foot achieved?
The bony arches also contribute to stability of the foot, distribute weight, increase flexibility and absorb shock. We have a lateral longitudinal arch, medial longitudinal arch and a transverse arch.
Ligaments and tendons of muscles help to improve and maintain stability.
Name the anterior compartment muscles of the leg and their insertions and innervation.
This is innervated by the deep fibular nerve (branch of the common fibular). These are extensors of the ankle and the toes. It is made up of 3 (+1) muscles:
- Tibialis anterior - originates from the tibia and IOM. The tendon crosses the ankle joint and inserts on the medial tarsal bones and the base of the first metatarsal
- Extensor digitrorum longus - originate from the lateral tibial condyle and fibula and inserts into toes 2-5. it extends the ankle joint and the toes.
- Extensor hallcuis (big toe) longus - fibula and IOM and inserts the big toe and the ankle.
- (Peroneus tertius)
Name the superficial posterior compartment muscles of the leg, their insertions, their innervation and their function.
The superficial group - 3 muscles
- Gastrocnemius - has two heads that originate from the medial and lateral femoral condyles - it is the most superficial muscle of the calf. Attaches to the femur and so can also act on the knee joint. They head from the inferior medial and lateral border of the popliteal fossa.
- Soleus - originates from the soleal line
- Plantaris has a long thin tendon. Originates on the distal part of the posterior femur
These all insert on the calcaneum via the central calcaneal (Achilles) Tendon. These muscles have the effect on plantarflexion in contraction. This is important in a muscle pump for venous return for the legs - especially gastrocnemius and soleus squeezing the blood back to the heart.
Innervated by the tibial nerve
Name the lateral compartment muscles of the leg.
There are only 2 muscles. They attach laterally to the fibula and are innervated by the superficial fibular nerve a branch of the common fibular nerve. The muscles include:
- Fibularis longus
- Fibularis brevis
Both are attached on the fibula. They hook behind the lateral malleolus and insert on the foot. Brevis interest on the 5th metatarsal and longus inserts across the plantar surface of the foot and onto the medial cuneiform and 1st metatarsal. They act to evert the ankle.
What are the major arteries of the leg?
The popliteal artery is the femoral artery once it has passed through adductor hiatus and through the popliteal fossa. It then gives rise to the anterior tibial artery. The anterior tibial travels through an aperture in the interosseous membrane to appear into the anterior compartment. It travels done the anterior compartment and appears at the dorsum of the foot as the dorsalis pedis artery. This is palpable on the foot. Look for extensor hallicis longus and palpate just lateral to it.
Once the popliteal artery has given off the anterior tibial artery it continues as the posterior tibial. The posterior tibial rise to the fibular artery which supplies the lateral artery. The posterior is harder to palpate behind the medial malleolus - here we find the deep posterior muscle tendons. It runs into the sole of the foot and terminates here as medial and lateral plantar arteries.
What are the major veins of the leg?
The deep veins follow the arteries. There are important superficial veins:
- The dorsal venous arch - can be seen under the skin on the dorsum
- The small saphenous vein - drains the lateral aspect of the dorsal venous ach. It travels behind the lateral malleolus and drains into the popliteal vein in the popliteal fossa
Medially is the great saphenous vein which drains the medial aspect of the dorsal venous arch. Found anterior to the medial malleolus. It travels up the medial leg and thigh to drain into the femoral vein.
What are the major nerves of the leg?
The sciatic nerve is the tibial nerve and the common fibular nerve bound together in the thigh which separate in the posterior thigh. The tibial nerve travels through the popliteal fossa straight into the posterior compartment of the leg and supplies the posterior leg. Then it travels posteriorly to the medial malleolus along with the posterior tibial artery and vein and the tendons. It goes into the foot and terminates as medial and lateral plantar nerves which innervate the foot muscles.
The common fibular nerve winds around the neck of the fibula. It runs around the superolateral borer of the popliteal fossa. It bifurcates into a deep branch which supplies the anterior leg and a superficial branch to supply the lateral leg. Behind the medial malleolus is the tarsal tunnel when there is passage of nerves, vessels and tendons form the posterior leg into the foot.
What are ankle sprains?
Ankle sprains is an injury to the ligaments. Most ankle sprains are inversion injuries. When our ankle is forced over in this direction, it tears or stretches the lateral ligaments. They may have significant swelling. If ligament detached from bone, fibres do not grow back into bone cortex as extensively - healed ligament are usually weaker, predisposing to dislocation as it is destabilised. Ligaments are relatively avascular and so healing takes a long time and so stability and gait are affected for a long time after. Torn ligaments destabilise joint - predispose to dislocation
What is the effect of medial ligament tears? How can this happen?
These are eversion injuries and are a lot less common. An eversion injury can pull the strong medial ligaments causing avulsion of the medial malleolus. The talus rotates laterally, fracturing the fibula. Injury to the deltoid and associated injuries to the medial malleolus and sometime the fibula.
What is Pes planus?
This is found in adolescents or adults. It can be of a rigid or flexible type, leading to a loss of medial longitudinal arch i.e. all of the foot is in contact with the floor. The flexible form is more common. The arch is present when not bearing weight but absent when standing.
There are many causes including loos or degenerating ligaments. It can be exacerbated by weight gain and/ore spending a long time standing. It may be asymptomatic, but can cause foot, ankle, knee and back pain (mal-alignment, reduced shock absorption). Treated with orthotics to support the arches.
