In the _acquired form_, the appearances are different, because the anterior part of the foot is usually flexed towards the sole, thus disguising to a certain extent the dorsiflexion at the ankle. This form is nearly always due to poliomyelitis, but it may also result from accidental division of the tendo Achillis. The anterior part of the foot is flexed towards the sole by the contraction of the plantar fascia and short muscles of the sole, the balls of the toes are approximated to the heel, and a deep transverse groove is formed in the sole opposite the mid-tarsal joint. The deformity presents a combination of the hollow foot--pes cavus--with pes calcaneus, and resembles that of a Chinese lady's foot. The foot rests on the heel and on the balls of the great and little toes, the sole of the foot being so deeply hollowed that even the lateral border does not touch the ground. In paralysis of the calf muscles alone, the tendons of the peronei or flexor digitorum longus may be divided and stitched to the calcaneus, to take the place of the tendo Achillis. If the calf muscles are not completely paralysed and the tendo Achillis is merely stretched, this tendon may be shortened by splitting it longitudinally and making the ends overlap, or its insertion may be displaced downwards. When the ankle is flail-like, it may be necessary to perform arthrodesis. Jones gets rid of the cavus deformity by resecting a wedge with its base towards the dorsum from the middle of the tarsus; the foot is then placed in a position of extreme calcaneus, the dorsum coming into contact with the front of the leg. Four weeks later a wedge is taken from the posterior part of the talus large enough to bring the foot down to a right angle with the leg; the articular surfaces of the tibia and fibula being denuded of cartilage, ankylosis takes place in a good position. #Pes Calcaneo-valgus.#--This deformity, which consists in a combination of dorsiflexion at the ankle and eversion of the foot, is as common as pure calcaneus (Figs. 148 and 149); the heel is depressed, the sole looks laterally, and its medial border is convex. Although it may be congenital, it is usually acquired as a result of poliomyelitis. The calf muscles are paralysed while the peronei retain their power, and, along with the tibialis anterior and the extensors of the toes, become secondarily contracted. Treatment is conducted on the same lines as in pes calcaneus, and the valgus may be controlled by implanting the peroneus brevis into the navicular. [Illustration: FIG. 148.--Pes Calcaneo-valgus with excessive arching of foot.] [Illustration: FIG. 149.--Pes Calcaneo-valgus, the result of Poliomyelitis.] #Pes Calcaneo-varus.#--In this rare deformity the heel is depressed and the sole of the foot looks inwards.