#Pes Equinus.#--This deformity, in which the foot is in the position of plantar-flexion with the heel drawn up and the toes pointed, is nearly always acquired as a result either of poliomyelitis or of spastic paralysis. In typical cases the patient walks on the balls of the toes (Fig. 145). It is seldom met with as a congenital condition. Occasionally it is due to nerve lesions such as peripheral neuritis, or to injuries and diseases in the region of the ankle, when the foot has been allowed to remain for long periods in the attitude of plantar-flexion. In a limited number of cases the equinus attitude is assumed to compensate for shortening of the limb. [Illustration: FIG. 145.--Bilateral Pes Equinus in a boy æt. 7, the result of Spastic Paralysis.] In _poliomyelitis_ the deformity is most often unilateral (Fig. 146), while in _spastic paralysis_ it is frequently bilateral (Fig. 145), and is usually accompanied by excessive arching of the foot--pes cavus--as a result of plantar-flexion at the mid-tarsal joint, and hyper-extension of the first phalanges and plantar-flexion of the second and third phalanges of the toes--"clawing of the toes." [Illustration: FIG. 146.--Extreme form of Pes Equinus in a girl æt. 8, the result of Anterior Poliomyelitis.] _Clinical Features._--In the mildest cases the patient is able to bring the foot to a right angle. In average cases the heel is raised off the ground, and the foot rests on the balls of the toes. In extreme cases, and especially when the extensors are completely paralysed, the toes may be flexed towards the sole, and the weight is borne on the dorsum of the foot (Fig. 146). The patient suffers from painful corns and callosities, and from inflammation of bursæ which form over the points of pressure. When unilateral, the patient compensates for the lengthening of the limb by flexing the knee and throwing the limb outwards in walking. In severe cases, especially when both limbs are affected, the patient may be dependent on crutches. The talus projects on the dorsum, the anterior part of its trochlear surface escapes from the tibio-fibular socket, and the calcaneus is drawn up so that it comes into contact with the bones of the leg (Fig. 147). [Illustration: FIG. 147.--Skeleton of Foot from case of Pes Equinus due to Poliomyelitis.] Shortening of the soft parts affects chiefly the muscles inserted into the tendo Achillis, the posterior ligament, and posterior parts of the lateral ligaments of the ankle. The fasciæ, ligaments, and muscles of the sole of the foot are also shortened. The flexors of the toes, the tibialis posterior, and the peroneus longus are shortened to a less degree. _Treatment._--Of all the deformities of the foot, pes equinus is that most easily rectified. In recent cases a great deal may be done by regular manipulations, and by the wearing of some corrective splint or apparatus between times.