lyz LAMENESS OF THE HORSE 



hones, to the proximal ends of the large and outer small meta- 

 tarsal bones. 



The tarsus is a true hinge joint and because of the great 

 stram which it sustains, is su])ject to frequent injury. About 

 seventy-fiye percent of cases of lameness affecting the hind leg 

 may be said to arise from disease of the hock. 



As members of locomotion the legs receive strains of two kinds : 

 those of concussion and weight-bearing and strains of propul- 

 sion ; the latter are the greater. In the horse as a work animal, 

 the hind legs are probably subjected to greater strains than are 

 the front but the manner of construction of the various parts 

 of the pelvic limbs with the possible exception (according to 

 some authorities) of the tibial tarsal joint, offsets this condition. 



The femur may be considered analagous to the humerus in 

 that it bears a similar relationship to the ilium, that exist be- 

 tween the humerus and scapula. Further flexion during repose 

 is prevented chiefly by the gluteus medius (maximus) muscle 

 and its tendons. The larger tendon inserts to the suuniiit of the 

 trochanter major of the fennir and corresponds to the biceps 

 brachii in the action of the latter on the seapulohuuieral joint, 

 except that the gluteus medius, in attnching to the femoral 

 trochanter, exerts its effect as a lever of the first class. Because 

 of the relationship between the long axes of the femur and iliac 

 shaft it is evident that the angle formed by these two bones 

 is maintained chiefly by the gluteus muscles during weight bear- 

 ing. Contraction of muscular fibers of the gluteus medius causes 

 extension of the femur and muscular strain is prevented to a 

 great degree by the inelastic portion of this muscle. The chief 

 physiological antagonistics of the glutei are the quadriceps 

 femoris and tensor fascia lata. 



While the leg is supporting weight the stifle joint is fixed in 

 position mainly by the quadriceps femoris group of muscles 

 which are attached to the patella. Tendinous fibres intersect 

 this muscular mass and relieve muscular sti'ain during weight 

 bearing. Because of the manner in which the patella function- 

 ates with the trochlea of the femur, comparatively little energy 

 is required to prevent further flexion of the stifle joints The 



