Surface Anatomy of the Knee and Foot
Foot and leg problems send a lot of people to medical professionals. Although a surface examination doesn’t tell the whole story, understanding the anatomy of the leg and foot will help you assess problems you patients might be facing.
The knee is easy to find right between the leg and the thigh. You can visualize the popliteal fossa on the posterior aspect of the knee — it’s a diamond-shaped area right over the part where the knee bends.
The popliteal artery can be palpated for a pulse, but it isn’t always easy to find unless the patient is lying prone with the knee bent. Press your fingers deeply into the popliteal fossa to feel the pulse.
Using the following clues, the bones are easy to find:
The condyles of the femur and tibia give the knee its shape, and they’re easy to palpate on either side of the knee; they’re the largest bony prominences on either side of the knee above the articulation.
The head of the fibula is located just inferior to the lateral condyles. It’s the bony prominence on the lateral side, just inferior to the knee articulation.
The patella is anterior to the knee joint and may be located by sight or palpation. It’s the bony kneecap located anterior to the knee joint.
The leg gets its shape primarily from the superficial posterior muscles that form the calf. They may be visible under the skin, along with superficial veins.
The foot and ankle
The foot and ankle have very little fat, so spotting both the medial malleolus and the lateral malleolus is fairly easy; the medial malleolus is the big bump on the medial side of the ankle and the lateral malleolus is the big bump on the lateral side of the ankle. The foot and ankle have little to no hair. The toes are each topped off with a toenail.
You can palpate (medically examine by touch) the following bones in the foot:
The head of the talus can be palpated just below the lateral malleolus when the foot is inverted (press your fingers into the flesh just distal to the malleolus while the sole of the foot is turned inward) or below the medial mallelous when the foot is everted (press into the flesh distal to the medial malleolus with the sole of the foot outward).
The medial tubercle of the calcaneus can be palpated by grasping the heel and pressing your thumb into the flesh on the medial plantar surface of the heel. You may not feel much unless the patient has a heel spur (bony overgrowth).
The tuberosity of the fifth metatarsal is palpable on the lateral side of the foot. It’s the most prominent bump on the lateral side of the foot, about halfway between the heel and toes.
The head of the first metatarsal forms a prominent bump on the medial portion of the foot — just at the base of the big toe. It may be inflamed and tender if the patient has a bunion.
The tendons of the extensor digitorum longus are usually visible (or at least palpable) where they run along the tops of the metatarsals. Just look for the tendons as they run along the dorsum of the foot from the toes to the ankle.
The great saphenous vein may be visible in a thin person, running just in front of the medial malleolus. The dorsal pedal artery may be palpated on the top of the dorsum of the foot. It can be found at the most prominent part of the dorsum, immediately lateral to the tendon of the extensor hallucis longus.
You may see a couple of different deformities affecting the feet:
A hammer toe is a deformity of a toe, usually the second one. The toe becomes stuck in a claw-like position as the interphalangeal joints are constantly flexed. It may be congenital but is usually due to wearing shoes that are too short. Hammer toes can be painful, especially when a corn forms on the top of the toe or a callus forms on the sole of the foot, just under the metatarsal. Hammer toes may be treated by choosing roomier footwear, using shoe inserts to cushion the toe, taking pain relievers, using corticosteroid injections, or undergoing surgery.
A bunion is a deformity of the first metatarsophalangeal joint. The bone becomes enlarged and forms a protuberance and may cause the big toe to become misaligned so that the big toe moves outward. The cause of bunions isn’t clear, but they’re more common in women. Bunions may cause no symptoms or they may be accompanied by redness, swelling, and pain. Bunions can be treated with rest, wider shoes, special exercises, and nonsteroidal anti-inflammatory medications.