Chap, xxiii.j THE ANKLE AND FOOT. 513 



foot, save one between the tendo Achillis and os calcis, 

 and another over the metatarso-phalangeal joint of 

 the great toe. The first-named bursa rises up about 

 half an inch above the os calcis, and bulges out on 

 either side of the tendon. When inflamed it may 

 produce symptoms like those of ankle-joint disease, 

 and when suppurating may lead to caries of the 

 os calcis. The enlargement of the bursa over the 

 metatarso-phalangeal joint of the great toe consti- 

 tutes a bunion. This condition is generally brought 

 about by improperly-shaped boots, which force the 

 great toe outwards, place it obliquely to the long axis 

 of the foot (with which it should be parallel), and 

 render the metatarsal joint very prominent. The 

 result of this deformity is a great weakening of the 

 toe and adjacent part of the foot, a lengthening of 

 the internal lateral ligament of the little joint, and 

 a displacement outwards of the tendon of the 

 extensor proprius pollicis. Bursae are often de- 

 veloped over the malleoli in tailors, and especially 

 over the external process, the part most pressed 

 upon when sitting cross legged. In club-foot, bursse 

 are found over any points that are exposed to undue 

 pressure. 



The tendons about the ankle are not infrequently 

 ruptured by violence. Those that most frequently 

 are so injured are the tendo Achillis, and the tendons 

 of the tibia! is posticus and long and short peroneal 

 muscles. The tendo Achillis usually breaks at a 

 point about one and a half inches above its insertion, 

 where it becomes narrowed and its fibres are col- 

 lected into a very definite bundle. 



In some forms of violence the synovial and fibrous 

 sheaths that birid down a tendon may be ruptured 

 and it be allowed to become displaced. This has hap- 

 pened to the tibialis posticus and peroneal muscles. In 

 each instance the dislocated structure comes forwards 



HH 4 



