21 8 journal of Agriculture. [8 April, 1907 



When a horse is lame in the shoulder, it is usually a one-side lame- 

 ness only, and is a result of one of three conditions, which are : — 



(I.) Shoulder Slip. 

 (II.) Sprain of the P'lexor Brachii or Biceps Muscle. 

 (III.) Injury to the Shoulder Joint. 



Shoulder Slip. 



The term "shoulder-slip" is apt to convey the impression of a dis- 

 location or partial dislocation (luxation) of the joint formed by the blade 

 bone (scapula) and arm tone {liurncrus^. In so far as it does convey any 

 idea of that kind, it is misleading ; dislocation of the shoulder joint being 

 a matter of very rare occurrence indeed. The term rather refers to an 

 outward slipping or oscillating movement of the shoulder joint at each 

 step when the weight is thrown on the affected limb. Why this slipping 

 movement occurs wnll perhaps be understood when it is explained that the 

 particular affection known as shoulder-slip occurs as a result of a sprain 

 of the muscles (the antea- and postea-sfinati muscles) covering the 

 shoulder blade and passing over the shoulder joint to be inserted to the 

 upper end of the arm bone below the joint. These muscles act as bind- 

 ing ligaments of the joint, and w-hen they are sprained and therefore 

 comparativeily powerless tO' firmly hold together the bones forming the 

 joint, the latter is apt to slip and oscillate uncontrolled during move- 

 ment. 



Causes. — Shoulder-slip, or more correctly shoulder sprain, is most 

 frequentlv caused bv over-strain or jerking during pulling. It is most 

 common in \oung farm horses being broken in to plough, which, by their 

 awkwardness and the unevenness of their footing, are likely to pull 

 jerkily. Wrenching of the muscles mav also occur on sudden and unex- 

 pected turning, or bv slipping when turning on uneven ground, or when 

 cantering over crab- holey country. 



Symptoms. — It must be borne in mind that the action of the muscles 

 which are strained is to draw forward the arm, and so assist in advancing 

 the hmb, and consequently, as a result of their powerlessness, the most 

 marked symptom during movement is a dragging of the limb, which is 

 swung outw^ards as it is brought forward. A " tied-up " action of the 

 shoulder joint, in the evident attempt to avoid much motion ; and the 

 oscillating motion pre!\douslv spoken of and explained, are also notice- 

 able. There is but slight droipping of the head, as there is little pain 

 w^hen the limb is brought to the ground. It is during action that the 

 pain mostly exists, and that the inabilitv is; most evident. When at rest 

 the limb hangs loosely, with the joints below the shoulder partly flexed, so 

 as to relieve the tension on the sprained muscles, and the foot rests on 

 the toe, and is placed a little behind its, fellow. The sprain, which is 

 at first shown by local pain, heat, and perhaps swelling, is quickly 

 followed bv a wasting of the muscles involved, which makes the spine 

 of the scapula stand out prominentlv. and gives the shoulder a shrunken 

 or wasted appearance when compared with its fellow. This shrunken- 

 ness and the accompanving absence oi bi-lateral svmmetry is well seen bv 

 standing straight in front and comparing the two shoulders. Lifting the 

 limb and forciblv flexing the shoulder and elbow joints, by putting strain 

 on the injured muscles, causes pain, evidenced bv flinching. 



