Anatomy clinical correlates: Foot

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Introduction0:00–0:28

The foot is the most distal part of our lower limbs - and while it represents only a small part of the body, its unique structure allows for walking, running, and dancing, but is also an unfortunate vulnerable point for being tickled.
Laughing aside, let's kick off this video which will focus on the clinical conditions affecting the foot. First, let's talk about plantar fasciitis.

Plantar fasciitis0:28–2:44

Plantar fasciitis describes inflammation of the deep plantar fascia, also called the plantar aponeurosis. The deep plantar fascia is a thick, pearly-white band of tissue that attaches to the medial process of the calcaneal tuberosity and extends to the toes and supports the medial longitudinal arch of the foot.
Excessive training, particularly those who frequently run, jog, or walk, can cause repetitive microtrauma. This leads to inflammation of the plantar fascia particularly at its attachment point to the calcaneus.
Additionally, individuals who undergo high impact exercise like jumping in volleyball or frequently train in bare feet may also experience plantar fasciitis.
Risk factors for plantar fasciitis include obesity, prolonged standing or working on hard surfaces, and pes planus, which is “flat feet” defined by the loss of the medial longitudinal arch of the foot where it contacts the groundDiagnosis of plantar fasciitis is often clinical, and it commonly presents in middle aged adults.
Individuals typically present with unilateral or bilateral heel pain that is worse in the morning and after prolonged rest, and gradually lessens with activity.
The pain is typically palpated over the medial process of the calcaneal tuberosity, but can be felt along the length of the sole of the foot, while pain can also be felt on passive dorsiflexion of the toes.
Heel spurs often coexist with plantar fasciitis, but it is also unclear whether they can cause plantar fasciitis, or represent a secondary response to an inflammatory reaction.Let's talk a bit more about pes planus, also known as ‘flat feet ', and is a term used to describe loss of the foot's medial longitudinal arch.

Pes Planus2:44–6:02

Flatfeet can be classified as either flexible, meaning they have normal appearance at rest but flatten with weight bearing, or rigid, which appear flat even when not weight bearing and has a reduced range of motion at the tarsal and subtalar joints.After birth, the appearance of flat feet is normal due to ligamentous laxity and a thick subcutaneous fat pad of the sole of the foot, and the most common type is flexible pes planus.Furthermore, conditions that may lead to congenital ligament laxity and exacerbate pes planus include Down syndrome, Marfan syndrome, or Ehlers Danlos syndrome.
Typically flexible pes planus resolves. As kids age, their fat pad is lost, the lax ligaments grow and mature, the medial longitudinal arch of the foot becomes visible, and a normal arch develops.
However there are many kids whose pes planus doesn’t resolve. This leads to acquired pes planus which persists into adulthood, though pes planus can also develop in adulthood without preexisting pes planus as a child.
Acquired pes planus is thought to be due to the breakdown of the foot supporting structures, such as the tibialis posterior tendon which provides dynamic support of the medial longitudinal arch, and the plantar calcaneonavicular ligament, also known as the spring ligament.
The breakdown of these structures may be due to obesity, trauma, degenerative or inflammatory arthropathies such as rheumatoid arthritis, or denervation such as a neuropathy caused by conditions like diabetes, all leading to a loss of the foot's medial longitudinal arch.
Now, pes planus is mostly asymptomatic, especially in children, but when it is problematic it typically presents with arch pain.
However, in time, it can alter the biomechanics of the lower limbs and lumbar spine causing pain or discomfort in the midfoot, heel, lower leg, knee, hip, and back.
On examination, there’s evidence of flat feet during rest, or excessive pronation of the feet during standing. One test that can be done is looking at the individual from the back and looking for the “too many toes” sign.
From this view only the fourth and fifth toe should normally be seen, but with flat feet and excessive pronation more toes will be seen.
Let’s switch gears and discuss hallux valgus, which is characterized by a valgus deformity of the big or great toe, and famously referred to as a bunion.

Hallux valgus6:02–8:58

Hallux valgus occurs when the proximal phalanx of the great toe deviates laterally on the first metatarsal, which deviates medially.
Think of the L in VaLgus to remind you of lateral deviation. Furthermore, there may be internal rotation of the toe so the toenail on the big toe faces medially, and as the big toe rotates medially the sesamoid bones shift laterally limiting their function.
Now, its exact etiology is unclear and the case of hallux valgus is likely multifactorial. It is most common in biological females and its incidence increases with age, and risk factors include genetic predisposition, ligamentous laxity, inflammatory joint disease such as rheumatoid arthritis, pes planus, abnormal gait and wearing poor footwear such as high heels.
Hallux valgus has a chronic and progressive onset, and even though it may be asymptomatic individuals often present with difficulty wearing their shoes due to the pronounced medial protrusion of their toe.
The pain associated with hallux valgus is chronic, sharp and often exacerbated by walkingThe deformity is often obvious on examination, and the skin overlying the medial metatarsophalangeal joint can become red and painful due to inflammation of the subcutaneous bursa protecting the joint, and it is this area that is considered the ‘bunion’.
The individual may also complain of a burning sensation on the dorsal side of the deformity due to compression on the medial dorsal cutaneous nerve.
As the hallux valgus deformity progresses, so does the pain and the size of the deformity. Blisters, ulcerations, and irritated skin adjacent to the deformity can also be present on examination, as can limited toe mobility.
Finally, inflamed thickened areas of skin can develop over the proximal interphalangeal joints of the other toes due to the altered mechanics of the foot, often over the little toe, and these are called corns.
Ok, quiz time! Can you recognize these three conditions?

Quiz8:58–9:09

(show an image of plantar fasciitis, pes planus, and hallux valgus). Now, let's discuss the lymphatic drainage of the lower limb, as damage to the lymphatic drainage can lead to something called lymphadenopathy.

Lower limb lymphadenopathy9:09–11:03

Lymphadenopathy is a common condition and it represents an abnormality in size, number, or consistency of lymphatic nodes within the body, and can be caused by things such as infection or malignancy.The lower limb has both superficial and deep lymphatic vessels.
The superficial lymphatic vessels follow the venous system and they receive lymph from the skin and subcutaneous tissue of the lower limb.
Now, the superficial system is further divided into a medial and lateral track. The medial track accompanies the great saphenous vein until it reaches the superficial inguinal lymph nodes, and bypasses the popliteal lymph nodes.
As a consequence, medial foot infections can cause inguinal lymphadenopathy. Alternatively, the lateral tract which drains lymph from the lateral leg and foot drains into both the popliteal and the inguinal nodes, so infections of the lateral foot first cause popliteal lymphadenopathy, and eventually inguinal lymphadenopathy.
The deep lymphatic vessels of the lower limb follow arteries and enter popliteal lymph nodes as well, and they receive lymph from the muscles and deep vessels of the lower limb.And finally, let’s ‘touch’ on the posterior tibial and dorsalis pedis pulses.
Lets start with the posterior tibial pulse.Ok, so the posterior tibial artery arises from the popliteal artery at the lower margin of the popliteus muscle.

Posterior tibial and dorsalis pedis pulses11:03–13:44

It then descends medially through the posterior compartment of the leg and enters the foot by passing posterior to the medial malleolus.
Now, the posterior tibial pulse can be palpated by pressing your fingers posterior to the medial malleolus in the space between the medial malleolus and the Achilles tendon, just above the calcaneus.
Furthermore, passively have the individual invert their foot, Which will relax the flexor retinaculum in order to better palpate the artery.
Next, is the dorsalis pedis pulse. The dorsalis pedis artery is a continuation of the anterior tibial artery which passes anterior to the ankle joint midway between the two malleoli and runs anteromedially.
It lies deep to the inferior extensor retinaculum, lateral to the extensor hallucis longus tendon, and passes to the first interosseous space.
The dorsalis pedis artery is fairly superficial and more easily palpated than the posterior tibial pulse. It can be palpated by starting at the midpoint between the two malleoli and pressing your fingertips roughly a third to halfway from this point to the web space between the first and second toe, just lateral to the tendon of the extensor hallucis longus.
If needed, you can ask the patient to extend their big toe to show this tendon, and you can then palpate lateral to it. Palpating these pulses is important as a weak or absent pulse typically indicates vascular insufficiency due to arterial disease, which will cause arterial occlusions proximal to these pulses.
Furthermore, obesity, edema, trauma, or other compressive lesions can result in a weak or absent pulse. Some individuals will have a congenital non-palpable pulse, however always remember non-palpable pulses are a late sign of acute arterial occlusion and may require urgent intervention.

Review13:44–15:52

Alright, as a quick recap. Plantar fasciitis is inflammation of the deep plantar fascia caused by repetitive microtrauma of the fascia.
It presents with unilateral or bilateral heel pain, with pain worse in the morning and after prolonged rest. Next, pes planus represents loss of the medial longitudinal arch of the foot, and can either be flexible or rigid.
It typically resolves in childhood, however it may progress to adulthood or develop in adulthood due to breakdown of the supporting structures of the medial longitudinal arch, such as the tibialis posterior muscle and spring ligament.
Hallux valgus is a valgus deformity of the big toe where it deviates laterally on the first metatarsal. It can present with an obvious medial deformity of the first metatarsophalangeal joint that gets worse with time, and is associated with pain, redness, and paraesthesia.
Lower limb lymphadenopathy is common in infection or malignancy. Medial foot lesions cause inguinal lymphadenopathy, while lateral lesions can cause both popliteal and inguinal lymphadenopathy.
And finally, the posterior tibial pulse can be palpated by pressing your fingers posterior to the medial malleolus in the space between the medial malleolus and the Achilles tendon, just above the calcaneus.
The dorsalis pedis pulse can be palpated by starting at the midpoint between the two malleoli and pressing your fingertips roughly a third to halfway from this point to the web space between the first and second toe, just lateral to the tendon of the extensor hallucis longus.