The foot and ankle are marvelous biomechanical creations. Tasked with forward propulsion, shock absorption, and providing balance for more than one hundred and twenty million steps in the average lifetime, it is a wonder that more people do not have more problems than they already have with their feet.
It is useful to divide the foot into the following three anatomic regions for evaluation: forefoot, midfoot, and hindfoot. Each region has its own unique pathology. Similarly, when evaluating the ankle it is helpful to consider whether the complaint is generated from an intra-articular or extra-articular source. In either case, a working knowledge of the anatomy is essential.
The forefoot includes the phalanges and the metatarsals. The midfoot boundaries include the tarsometatarsal joint (or Lisfranc joint complex) and the midtarsal joints (talonavicular and calcaneal-cuboid joints). The hindfoot consists of the talus and calcaneus (Figure 7–1).
The ankle (tibiotalar) joint is largely responsible for dorsiflexion and plantarflexion of the foot. The joint itself is composed of the distal tibia, the distal fibula, and the talus. Inversion and eversion motion of the foot occurs cooperatively through the subtalar (talocalcaneal), talonavicular, and calcaneal-cuboid joints. The joints in the midfoot region contribute very little to foot motion.
There are five major peripheral nerves that innervate the foot. Three of these run superficial to the fascia (sural nerve, superficial peroneal nerve, and saphenous nerve) and two are deep to the fascia (the posterior tibial nerve and the deep peroneal nerve) (Figure 7–2).
Cutaneous innervation of the foot. Key: (1) Saphenous nerve. (2) Deep peroneal nerve. (3) Superficial peroneal nerve. (4) Medial plantar nerve. (5) Lateral plantar nerve. (6) Calcaneal branch (tibial nerve). (7) Sural nerve.
Metatarsalgia is plantar pain under the metatarsal heads or under the “ball” of the foot from abnormal loading. This term is often used incorrectly to describe any plantar forefoot pain and should be reserved for pain localized under the metatarsal heads with loading from standing or gait. Although multiple etiologies of forefoot pain exist, symptoms from metatarsalgia are typically under the second or third metatarsal heads. Careful physical examination reveals tenderness directly under the metatarsal head with less or no tenderness dorsally, with toe motion, or with palpation in the web spaces. The differential diagnosis is extensive but includes stress fracture, metatarsophalangeal joint (MTP) synovitis, Freiberg disease, Morton neuroma, bursitis/neuritis, and either degenerative or inflammatory arthritides of the MTP joints. Metatarsalgia is commonly seen with hammertoe deformities due to plantar displacement of the metatarsal head secondary to tendon imbalance. It is also commonly associated with bunion deformity as increased angulation leads to decreased load bearing by ...