History
Has the horse been rested or exercised during this lameness period. Has the lameness worsened, stayed the same, or improved. Cases where a marked improvement has occurred usually have a better prognosis than cases that have remained static or worsened.
Signalment
Age, breed and use can provide insight into the probable cause of the lameness. For example, an aged quarter horse gelding used for ranch work and trail riding with a chronic history of lameness will have a higher incidence of foot problems, and problems associated with low motion joints (i.e., pastern and distal tarsal joints). In contrast, racehorses presenting for lameness will have a higher incidence of problems associated with high motion joints (e.g., carpus and fetlock) and palmar soft tissue support structures (e.g., flexor tendons and suspensory ligament). Stress fractures of the long bone also need to be ruled out. Endurance horses frequently sustain sprain and strain injuries. Occasionally, however, they will present with a history of acute nonweightbearing lameness with limited improvement in lameness. In this situation, phalangeal fractures ranging from fissure to complete must be ruled out. Young, growthy horses that have developed lameness during early training will have to have osteochondrosis ruled out as the cause.
Visual examination
At rest, the horse should be standing squarely on a flat surface. Each limb is compared to its opposite member. Feet are observed for size, abnormal wear, balance, hoof cracks and heel bulb contraction. All joints and tendons are visually inspected for swelling and muscles of the limbs, back and hindquarters are observed for swelling and atrophy. Each abnormal finding should be ruled out as a cause of lameness during exercise and palpation examination.
Exercise
The main objective in exercising the horse is to identify the limb or limbs involved and the degree of lameness and incoordination in movement. The horse is observed at a walk, trot and in some cases under tack or on the treadmill. Additionally, the horse is exercised at a trot in a circle to the left and right. This can be done on a lunge line (preferred) or hand-held. Also, exercise up and down on an incline can be helpful. Proper examination includes watching the horse from the front, side and rear. In general forelimb lamenesses are best viewed from the front and side and rear limb lamenesses are best observed from the side and rear. The examiner is looking for head nodding, gait asymmetry and animation, alterations in height of the foot flight arc, phase of stride, joint flexion and extension angle, foot placement, foot contact and loading, degree of fetlock extension with weightbearing, action of the shoulder muscles, and symmetry in gluteal rise and use.
Joint flexion angles are best viewed from the side and may or may not be associated with alterations in the hoof flight arch and phase of stride. In some cases horses compensate with an increased flexion of the affected limb and decreased flexion of the unaffected limb. One limb is compared to the other and the degree of flexion is assessed. In others, such as in bone spavin, a decreased height of foot flight arch and shortened cranial (anterior) phase to the stride might be subtle but an obvious decrease in tarsal joint flexion angle is noted.
Fetlock extension is best viewed from the side. Since the degree of extension is a function of weight bearing (greater weight bearing = greater extension), a horse with a weight bearing lameness will have less extension of the fetlock in the affected limb. In my experience, this is a very sensitive indicator of the lame limb.
To identify a hind limb lameness it is most helpful to observe the horse from the rear to compare the symmetry of gluteal rise and duration of gluteal use (movement of the croup). The gluteal rise is evident during the swing phase; and the use is evident during the support phase of the stride. This observation is best made on a level surface and standing so the examiner can visualize the upper most excursion of the gluteal muscles. The head and neck must be in axial alignment (straight) with the body. With pain, most horses attempt to get off the affected hind limb more quickly and the gluteal muscle contraction is shortened, which leads to a shortened duration of gluteal use and a visual “hip roll” or hip “drop off.” Following this, there is a rapid elevation of the hip and gluteals recognized as a “hip hike” or “upward flick.” There are 3 different situations I recognize: (1)A depressed gluteal rise and a decreased duration of gluteal use; (2) A symmetrical gluteal rise equaling that of the opposite hip but a decreased duration of gluteal use; (3) A rapid and increased gluteal rise (hip hike) where the affected limb gluteal is brought up rapidly but the duration of gluteal use is shortened.
Handling the horse
The handler plays an important role in assisting in lameness diagnosis. In general horses should be held loosely with their heads centered on line with their body and exercised as slow as practical. If the head and neck are allowed to sway from one side to the other this creates an asymmetric gait. If the handler holds the horse too tightly subtle head nodding is difficult to observe. Fast trotting or cantering makes it more difficult to focus in on limb movement but in some cases it is helpful in identifying neurological deficit because it requires more coordination for movement to occur. The handler should be in front of the horse's shoulder so the movement of the horse's front limbs will be easily seen and the handler should not look at the horse.
Circling the horse at a trot accentuates low-grade lameness usually on the inside limb. Lunging the horse is preferred to the handler jogging with the horse in a circle. The horse should be relaxed at a jog starting with a large circle that gradually gets smaller. The smaller circle will sometimes reveal a lameness not seen in a larger circle. The handler should not excite the horse with voice commands or excessive use of a whip. Lamenesses that may be more evident when the limb is on the outside of the circle include: high suspensory ligament desmitis, desmitis of a collateral ligament, medial carpal injury, medial splint bone or medial proximal sesamoid bone problems.
If the horse is flighty and apprehensive, give 15–20 mg of acepromazine IV, wait 15–20 minutes, and then resume the examination.
Selection of surfaces
In most cases the evaluation of lameness is best carried out on hard surfaces. It provides more concussion than a softer surface plus it affords the examiner the opportunity to listen to as well as visualize foot placement. There is usually an obvious difference in the horse's landing between the unsound and sound limb. The unsound limb makes less noise because less weight is taken on that foot. On the other hand there is a louder noise elicited when the sound foot hits the ground because it is bearing more weight. This is true for both fore and hind limbs. Since hard surfaces typically do not apply good sole and frog pressure, horses with suspected foot problems can be exercised on gravel surfaces to accentuate the lameness. This is particularly true of horses with chronic symmetrical conditions involving the feet. When exercised on asphalt they may travel with a stilted, shuffling-like gait but appear comfortable. When placed on gravel bilateral lameness becomes quite evident. Foot placement is also best observed on hard surfaces; softer surfaces tend to envelop the foot making placement more difficult to see.
Grading lameness
The degree of lameness should be recorded. For some, simply using mild, moderate and severe may suffice. However, a more objective approach utilizing a grading system may be helpful in describing degrees of lameness. This system is beneficial because it standardizes the classification as to degrees. It makes record keeping easier and allows the examiner to come back at a later time to assess the degree of improvement. The following is AAEP's guidelines for grading lameness.
Grade 0: Lameness is not perceptible under any circumstances.
Grade 1: Lameness is difficult to observe; not consistently apparent regardless of circumstances (i.e., weight carrying, circling, inclines, hard surface, etc.).
Grade 2: Lameness is difficult to observe at a walk or in trotting a straight line; consistently apparent under certain circumstances (i.e., weight carrying, circling, inclines, hard surface, etc.).
Grade 3: Lameness is consistently observable at a trot under all circumstances.
Grade 4: Obvious lameness; marked nodding, hitching or shortened stride.
Grade 5: Minimal weight; bearing in motion and/or at rest; inability to move.
Palpation, manipulation and flexion tests
Limbs
All regions of the limb should be palpated for swelling, pain on pressure and symmetry. Symmetry is documented by palpating the same region on the opposite limb. Digital pulses should be palpated before exercising the horse. All joints should be manipulated (e.g., rotated, flexed and extended in some cases) and painful responses documented. Hoof testers examination should be done in a systematic fashion. Experience is required to determine the amount of pressure to apply. A persistent nonfatigable response (limb withdrawal) to hoof tester pressure indicates a painful response. This response is compared with the response elicited with hoof tester pressure on the opposite foot. Flexion tests of all joints is done. Generally, the joint is held in flexion for 30 to 60 seconds depending on the joint being tested and the examiner's preference. The initial response to flexion (painful, stiff, etc.) and degree of flexion is documented. After the flexion test, the horse is trotted and the degree of lameness is documented. A positive flexion test is one where the lameness is exacerbated for at least 10 to 20 steps and in some cases is lasting. For the fetlock and phalangeal joints, they are flexed until the horse just begins to withdraw the limb. The flexion is maintained for 30 seconds. The upper limb joints are flexed and lameness documented. The hock flexion test is done by holding the bottom of the foot at the toe region or by placing the hand or hands around the plantar fetlock region. Maximum hock flexion is required for a good test. To achieve this, the metatarsus should be parallel to the ground, the limb is placed slightly axially to maintain balance, and it is pulled cranial until resistance is met. A stifle flexion test can be done by grasping the distal tibia and pulling the limb backward and upward until maximal stifle flexion is achieved.
For the cruciate test, the examiner stands cranial to the affected limb and one hand is placed on the proximal tibial tuberosity to push the tibia caudad as quickly and forcibly as possible and let go; the other hand is used pull the tail toward the affected side to force the horse into weight bearing. The caudal and rebound forces cause stress to the cranial and caudal cruciate ligaments. This is done 15 to 20 times after which the horse is trotted off and the degree of lameness observed.
Pelvis
The pelvis is examined externally. First, the symmetry of the greater trochanters, the tuber coxae and tuber ischii are checked. Asymmetry of these prominences should make the examiner suspicious of fracture or dislocation. Firm pressure is then applied to these prominences and the horse’s response is recorded. If swelling is present in the perivaginal tissues in the mare as well as edema of the vaginal mucosa, one should be suspicious of a symphyseal fracture of the pubis (rare condition). In the mare this can be confirmed by a vaginal examination in conjunction with hind limb manipulation by an assistant. Fractures of the ileum and acetabulum can also be picked up by rectal exam, which is covered in greater detail later.
Examination of the back
First, the horse's back is observed for contour from the side and axial alignment from the rear. Next, the tips of the dorsal spinous processes are palpated for longitudinal alignment, protrusion or depression, and interspinous distance. Malalignment of these processes may indicate fracture and luxation or subluxation or overlapping of the dorsal spinous processes. Then the reaction to gentle running of the fingertips of both hands down the back from the withers to the base of tail is assessed. Thin skinned, hypersensitive horses will tend to cringe when this is done but without a dramatic response such as rearing or kicking or withdrawal it should not be considered as clinically significant. Any muscle swelling, atrophy or asymmetry is noted. Following this, with the fingers flattened and held together firmer pressure is applied to the dorsal muscles in the same manner as mentioned. Most horses will respond to this pressure in the lumbar region by dorsiflexing their backs. However, after a few repeated applications of hand pressure this response fatigues and withdrawal is not prominent. Special attention is paid to the insertion of the longissimus dorsi muscles on sacral vertebra 2 and 3. For those horses that appear to be sensitive, a gradual increase in finger-applied pressure is in order. If back sensitivity continues and minimal reduction in response is observed, this should be considered clinically significant. As with any of these tests each animal responds somewhat differently and therefore the assessment does require clinical experience for the subtle case. In some cases, tightening (muscle spasms) of the longissimus muscle is felt rather than withdrawal. This usually signifies that the horse is attempting to fix the vertebral column because dorsiflexion and withdrawal from pressure is painful. Finally, finger tip pressure is applied to the epaxial muscles lateral to the dorsal spinous processes and the response is observed.
Flexion and manipulative tests
With these tests the examiner is attempting to gain an appreciation for the horse's willingness to ventroflex, dorsiflex and lateral flex its thoracolumbar vertebra. The assessment of the horse's ability to ventroflex the back is obtained by pinching the muscles in the thoracolumbar region. For dorsiflexion of the back, the horse is either pinched over the croup or a blunted instrument is run over this region. This creates a dorsal arching of the thoracolumbar region and a coupling under of the croup region. Lateral flexion is assessed by firm stroking of the lateral lumbar musculature and/or lateral thoracic region. This procedure is performed on both sides with a blunted instrument. Skin sensation assessed by utilizing a sharp object causes withdrawal rather than flexion and therefore it is undesirable. Horses normally resent this test and the desired flexure is observed.
Reluctance to flex associated with muscle tightening and back rigidity often indicates a bony lesion in the thoracolumbar spine. In some instances the site of pain can be localized by selective finger pressure but frequently radiographs or nuclear medicine scans are needed. Tail elevation usually causes the horse to couple under behind. However, with damage of the sacrococcygeal region the dorsal lifting of the tail often results in a camping out behind.
Intermittent force full downward hand applied pressure to the tuber coxae will allow you to access the relative movement of the sacroiliac (SI) joint. Normally, a subtle bouncing action is felt. Horses with pain in the SI region will resent this manipulation and no movement will be felt.
Rectal exam should be carried out on all cases of suspected upper rear limb involvement and back problems to rule out luxations or fractures of the sacral vertebra and fractures of the pelvis. Oftentimes a painful response can be elicited by palpation of the sublumbar muscles in those horses suffering from myositis.
Examination of the Neck
The neck is visually examined for contour from the side and axial alignment from the front and rear. Excessive ventral arching of the neck in the mid-cervical region is seen in some cases of cervical vertebral malformation (CVM). A straight (extended) poll can be seen with atlanto-occipital and atlanto-axial malformations. Axial deviations of the neck are most commonly the result of a development problem (e.g., hemivertebrae) or trauma. Splinting and spastic contraction of the neck muscles with or without signs of spinal ataxia is consistent with vertebral fracture. Generally these horses are very painful.
Palpation is done to identify muscle atrophy or swelling and to document the alignment of the vertebrae. Muscle atrophy is most often observed in the caudal neck region dorsal to the cervical vertebrae. The atrophy may be symmetric or asymmetric (affecting one side). Causes for muscle atrophy include; CVM, arthritic articular facets and equine protozoal Myelopathy (EPM). Swelling of the neck either lateral or ventral is generally a sign of trauma and or infection. The transverse processes of the vertebrae are palpated for alignment and symmetry.
The neck should be flexed laterally and ventrally and extended to assess flexibility, range of motion and pain. Lateral flexing can be done by pulling the horses head by the halter to one side then to the other. Alternatively lateral neck flexion can be encouraged holding a carrot or apple at the horses shoulder. Most horses can lateral flex their neck enough that the muzzle almost contacts the craniolateral shoulder region. Ventroflexion is assessed by feeding the horse at ground level and extension is evaluated by elevating the head and neck. Resistance to neck movement in any direction may be a result of pain or extensive degenerative changes in the articular facets.
Rectal exam
The rectal exam can be a very important part of the lameness evaluation particularly if myositis, fractured vertebra, thrombosis of the iliac arteries or pelvic fracture is suspected. The horse is first examined while standing still and the exam begins in a cranial to caudal direction. Pressure is applied to the iliopsoas muscle located cranial to the pelvic brim. If painful, with the horse assuming a splinting position, local myopathy, or fracture of the lumbar vertebra should be suspected. In some cases of fracture there will be ventral swelling associated with the lesion. The aorta is checked for pulsation. If a strong pulse is not present in one of the iliac arteries, thrombosis should be suspected. In the older horse the sublumbar nodes are checked for any asymmetry, which may indicate metastasis of a tumor, particularly in one side to the other. With displaced ileal fractures an obvious asymmetry is present. If a hairline pelvic fracture is present, manipulation of the limbs may cause crepitation or result in enough separation in the fragments so that this can be felt digitally. The ventral aspect of the sacral vertebral bodies are checked for alignment and any depression or extension into the pelvic canal may indicate fracture or subluxation. If any question still exists the examination continues first with the horse being rocked from side to side by alternate pressure applied to his tuber coxae. In some cases, it is beneficial to walk the horse while the hand is still in the rectum to identify any pathology.
References
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