FRANK J. MILNE STATE-OF-THE-ART LECTURE


Fig. 2. A six year old showjumper mare (A) on the lunge and (B) ridden in left canter. Note the horse’s croup high posture. In canter to the left and to the right the horse felt on the forehand and very stiff in the back. She was unwilling to engage the hindlimbs. In trot the horse stepped slightly short behind and lacked hindlimb impulsion. The horse had bilateral proximal suspensory desmitis and sacroiliac joint region pain. Her performance was dramatically improved after bilateral perineural anal- gesia of the deep branch of the lateral plantar nerve and infiltration of local anaesthetic solution around the sacroiliac joints.


shortened cranial phase of the stride of the lame hindlimb may be exaggerated. It is also crucial to recognize the influence that forelimb lameness can have on the hindlimb gait and the effect that hindlimb lameness can have on forelimb gait. It is well recognized that hindlimb lameness can induce a head-nod mimicking ipsilat- eral forelimb lameness.6 It is less well recognized that forelimb lameness may induce asymmetry of the hindlimb gait. By observing the horse under a variety of circumstances, it may be possible to dif- ferentiate between genuine concurrent forelimb and hindlimb lameness and an apparent lameness that is secondary. However, it may or may not be pos- sible to determine whether there is concurrent fore- limb and hindlimb lameness without using local analgesia. Thus, each lameness must be graded independently initially, in the knowledge that abo- lition of pain in, for example, the hindlimb may abolish both the hindlimb lameness and the appar- ent (secondary) forelimb lameness. Assessment of a horse moving on the lunge can


help to determine if a head-nod present in conjunc- tion with a hindlimb lameness is related to the hindlimb lameness or reflects a forelimb lameness. If the hindlimb lameness deteriorates on the lunge but the head-nod remains unchanged, or if the head- nod is worse but the hindlimb lameness stays the same, it can probably be concluded that there is coexistent forelimb and hindlimb lameness. This requires verification with the use of local analgesic techniques, further discussion of which is beyond the scope of this commentary. Although overt lameness is rarely seen on the


lunge in canter, assessment of canter and transi- tions from trot to canter and canter to trot can give useful additional information. A bilateral forelimb lameness may manifest as a short-striding, jarry canter. Hindlimb lameness may result in the hindlimbs being placed closer together than normal,


so-called “bunny-hopping” when extreme. There may be reduced extension of the distal limb joints of the lame hindlimb, especially with the lame limb on the inside of a circle. The fetlock may appear to knuckle forward slightly during the stance phase, with incomplete loading of the heel. Alternatively the horse may be on the forehand and croup high in canter (Fig. 2). Curiously this gait adaptation is sometimes also seen in a horse with bilateral fore- limb lameness. The horse may repeatedly become disunited (ie, change legs behind, while maintaining the correct forelimb lead); however, this may be a normal feature of a young unbalanced horse that lacks hindlimb strength and coordination. Irregu- lar steps behind in a transition from trot to canter or from canter to trot are a manifestation of hindlimb lameness. Stepping short behind and maintaining a croup-high posture in a downward transition may reflect bilateral hindlimb lameness. Mild hindlimb lameness may still be barely de- tectable, and assessment of the horse ridden may be crucial. It is important to recognize the influence of the weight of a rider on hindlimb gait, especially when in rising trot. The lameness is usually accen- tuated when the rider sits on the diagonal of the lame hindlimb and the horse feels more uncomfort- able to the rider on this diagonal. The horse may adjust its rhythm to try to shift the rider back to the opposite diagonal. A heavier rider is more likely to accentuate lameness than a lighter rider. A subtle lameness may still be unapparent and riding con- secutive 8- to 10-meter diameter circles to the left and to the right may induce irregularities of rhythm reflecting lameness and a change in the speed, with the horse slowing down when uncomfortable. Like- wise, performing so-called lateral movements such as shoulder-in, travers, and half-pass may induce gait irregularities that are otherwise not apparent. In some horses, the only manifestation of a hindlimb gait abnormality may be a tendency to change limbs


AAEP PROCEEDINGS  Vol. 59  2013 95


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