The ambulatory practitioner is most often the first responder for lameness issues. A well-equipped ambulatory service can perform sophisticated and thorough diagnostic lameness evaluations in many cases. Attention to detail and a willingness to spend a little extra time on the investigation of lameness can be professionally rewarding. Advice will be given on examination techniques and essential equipment and procedures.
Ambulatory practice presents lameness cases daily that offer an opportunity to provide excellent diagnostic services to the client and, in most cases, a definitive diagnosis. The ambulatory clinician needs to be prepared to do a thorough evaluation in terms of both time and equipment. Basic needs include the observation and palpation skills of the practitioner, hoof testers, shoe removal equipment, supplies to properly perform diagnostic anesthesia and time to perform a thorough examination. Today’s technology allows the ambulatory practitioner to have a great deal of sophisticated diagnostic equipment at his or her fingertips, including portable digital radiography, diagnostic ultrasound and even commercial objective lameness detection devices. These devices can now be compact and battery-powered, making field use simple. The addition of experienced technical assistance, such as a veterinary technician, can make the process of lameness diagnostics much more efficient and accurate, as well as professionally fulfilling.
It is important to be prepared to work up lameness thoroughly and be mindful that such examinations can be time consuming.
Appropriate scheduling is essential.
THE ACTUAL EXAMINATION
The first step in an evaluation for lameness or poor performance should be a simple visual examination of the horse while collecting some historical information. Observing the horse in its stall may give the examiner some clues regarding the horse’s level of comfort by how it stands or rests a limb. Watching the horse step out of its stall may offer more information; for example, the horse with palmar foot pain may take several short steps as it first walks out of the stall. An overall assessment of body condition and symmetry of structure can provide much information about possible chronic issues. After the visual inspection, a palpation examination should be performed. The author uses a modification of an “acupuncture” examination or “scan” that allows for complete palpation of the horse while eliciting responses from potentially painful areas. Such an examination includes palpation of the poll, neck, torso, hind quarters and lower limbs in a repeatable manner, the goal being to go over the horse in a systematic fashion. The results of this stage of the examination may reveal painful areas in the neck, back or hindquarters and should be noted.
A thorough palpation examination of each limb is conducted. Careful inspection of the feet for balance and symmetry should be performed. Flexion manipulations can then be performed in a “passive” sense, not asking the horse to walk or jog away, while noting any resistance or painful responses. It may be appropriate to use hoof testers at this point before starting any exercise. If a profound digital pulse is noted with heat and hoof tester responses, there may be a clear indication for shoe removal and inspection of the hoof and sole even at this stage, such as when a hoof abscess or severe bruise is suspected.
Next, the horse can be moved in hand at a walk and trot, taking note of any obvious lameness or unusual foot flight or limb motion. Keep in mind that some lameness conditions can be confused with neurologic gait deficits. The examination is best performed on hard footing, if available. It is useful to see the horse walk in circles as well as on straight lines. Likewise, jogging the horse in circles as well as in a straight line may provide much more insight related to the horse’s level of comfort. Repeating these steps on softer footing may offer further information. Some horses are fractious and may be even difficult about the in-hand examination. The author frequently gives a small dose of sedative, detomidine hydrochloride, 1.5 mg total dose, to evaluate lameness if the horse is not well behaved. This small dose of sedative relaxes most horses but does not reduce evidence of lameness in the author’s experience.
The next step is to perform active flexion tests of all limbs with the horse walking or trotting away and observing for any evidence of lameness. A positive distal limb flexion, as an example, may indicate a problem in any number of sites, from the distal interphalangeal joint (DIPJ) to even the proximal suspensory ligament. Flexion tests are a tool for regionalization and enhancement of the observation process but are not specific.
Care should be taken not to overexert the very lame horse (greater than 3/5) until a good sense of the nature of the problem is recognized. The very lame horse may be a candidate for immediate imaging if there is a high suspicion of a problem based on presentation and initial inspection.
Following flexion tests, it may be advisable to observe the horse work on a lunge line and under saddle. Some horses are difficult to lunge and may pose a hazard for injury to horse and handler.
Again, these horses should be lightly sedated or simply watched under tack. Many lameness conditions are not otherwise apparent until a rider is aboard or the horse is asked to do more work.
The riding examination may give the veterinarian a great deal of information not otherwise apparent during the in-hand exam.1 Certain safety precautions should be taken, such as proper headgear for the rider and tack for the horse, and all involved should acknowledge that the riding examination is needed to further evaluate the lameness. The author’s clients pretty much expect a riding examination in cases of vague lameness, and the potential for injury working around horses is understood. Such an examination may require some training and experience in observing horses working under saddles but can prove most useful in arriving at a conclusion of the likely origin of performance discomfort.
Rider weight may change the balance of the horse in such a way as to augment lameness. Weight on the back may be a source of discomfort and may be demonstrated by a change in the shape of the back, height of head carriage, shortening of stride or disobedience. The horse should be asked to perform the various gaits while under saddle and carefully observed for changes in the level of lameness with each gait, transitions from one gait to another and directional changes. Rider position and balance may affect the appearance of lameness. The author frequently asks for a sitting trot, rising trot and rising trot on the wrong diagonal. While some investigators have suggested that there is no greater challenge for the back at a sitting trot as opposed to the rising trot,2 the constant pressure results in neck extension and a change of gait and behavior in some horses. Canter work may be quite different under saddles as opposed to on the lunge, showing a more stabbing or foreshortened gait, lead swapping or bucking.
For the horse that demonstrates little or no real lameness but for which there is a performance complaint, it may be advisable to watch this horse perform more serious work such as jumping or more engaged and lateral work for the dressage horse. Disturbed performance or disobedience may be evident in cases of neck, back or sacroiliac-related discomfort. Some organic issues such as gastric ulcers may cause similar behavior when worked under saddle, which may mimic a sore back.3 Watching the horse on different footing surfaces, ranging from turf to non-slip paved or compressed surfaces, may also reveal lameness characteristics not previously noted. Horses that are more obviously lame under saddle may be candidates for diagnostic analgesia.
At this stage of the examination, the veterinarian should have a good sense of the severity and possible location of any lameness and may proceed with further diagnostics, such as diagnostic anesthesia. If the degree of lameness suggests that further damage may occur with exercise while regions are desensitized, it may be advisable to go straight to radiography or ultrasound in select cases.4,5 Some practitioners may elect to offer treatment now based on the overall assessment, and the client or trainer should be advised that while not illogical, the process is somewhat speculative. Keep in mind that a thorough examination has value, and there is nothing unprofessional about charging appropriately for time spent.
Diagnostic nerve blocks are the author’s next procedure of choice following the physical examination if they are deemed safe relative to the severity of the lameness and necessary for more specific localization. Severely lame horses may be at risk because of structural instability and could sustain further injury if desensitized and exercised in some fashion. In some cases, such as a painful and swollen flexor tendon, physical examination and diagnostic imaging may be sufficient to establish a clear diagnosis.5 Many lameness conditions look and flex alike but are not of the same origin. If the lameness is of sufficient grade to produce a clear contrast and has not improved with exercise, (i.e., warming up), the examiner should proceed with diagnostic nerve blocks.
DIAGNOSTIC ANESTHESIA
Distal limb regional anesthetic techniques are straightforward to perform and applicable for use in the field in all but the most fractious of horses. Mild sedation of more difficult horses may aid the process and still permit a functional examination as previously mentioned. Time is probably one of the most critical considerations in performing diagnostic anesthesia in the field, and the practitioner needs to commit to the process and not be constantly watching the clock. Each nerve block will consume at least 10 to 15 minutes from preparation to effect and intra-articular blocks will take longer. Again, this is an activity that is greatly enhanced by having a technician experienced in such procedures.
Depending on the practitioner’s comfort level and experience, most limb nerve blocks can be performed easily in the field with proper preparation. Take time to prepare the site appropriately using suitable cleaning and disinfecting agents. The author prefers mepivacaine as a local anesthetic because of its relatively rapid onset of action and minimal postinjection reactions. A significant majority of lameness problems occur in the distal limb, and the time required to perform several nerve blocks may provide valuable insight into the potential cause of lameness and a satisfying experience for the client. In some cases, it may be necessary to repeat the riding examination after diagnostic nerve blocks to fully assess the response. Care should be taken when performing multiple blocks because the horse may lose some proprioception. After localizing the site of lameness, decisions must be made regarding further investigation.
FURTHER DIAGNOSTIC PROCEDURES
Various procedures may follow regionalization of the source of lameness. These may include simply removing a shoe and identifying an abscess or solar bruising or proceeding to prepare the foot for radiographic or ultrasonographic examination. Radiographic imaging is indicated for a variety of causes of foot-origin lameness, and the ambulatory practitioner can take the opportunity to provide an excellent technical service. Again, taking time to properly clean and prepare the foot (i.e., pulling shoes, trimming, wire brushing and packing with Play-Doh) is essential for obtaining quality images. Today’s digital technology provides little excuse for poor radiographic quality; when it occurs, it is most often related to technique. Lesions are often subtle, and high-quality images improve the likelihood of diagnosis.
The same principles of proper positioning and technique that apply to imaging more proximal areas also apply to the distal limb. In addition to identifying a potential cause of lameness, high-quality foot radiographs may help guide the farrier in trimming and achieving appropriate foot balance.
Diagnostic anesthesia and the absence of radiographic lesions may suggest that lameness is of soft tissue origin and may be better evaluated with diagnostic ultrasonography. If the suspected area has been infiltrated with local anesthetic,
it may be prudent to perform ultrasound imaging at a follow-up visit. Alternatively, imaging may be performed before blocking a specific area if there is a high degree of suspicion that soft tissue structures are involved. Ultrasonographic evaluation of the solar surface for assessment of the podotrochlear apparatus requires careful preparation to adequately moisten the foot and will likely require a return visit.
As with obtaining good radiographs, successful ultrasound imaging requires proper preparation. Thorough cleaning and moistening of the area to be examined are essential. In winter months, clipping hair will be necessary, and clipping often improves image quality regardless of the season. Adequate time must be taken to obtain clear, repeatable images; a hurried examination may result in reduced quality.
DIAGNOSIS & RECOMMENDATIONS
By this stage, the practitioner should have a short list of probable causes for the lameness or poor performance complaint. After consultation with the trainer or client, appropriate therapy may be instituted, or a decision may be made to refer the case to another practitioner for more in-depth diagnostics such as nuclear scintigraphy, MRI, CT, PET scans or gastroscopy. Often, a reasonable therapeutic plan can be developed to address specifically identified issues. Follow-up examinations and treatment may be indicated before reaching definitive conclusions.
REFERENCES
- Mitchell RD, The role of the ridden lameness evaluation, Proceedings of BEVA Congress, Sept 2015
- De Cocq P, Prinsen H, Springer NCN, van Weeren PR, Schreuder M, Muller M, and van Leeuwen JL (2009), The eff ect of rising and sitting trot on back movements and head neck position of the horse, Equine vet. J 41(5) 423-427
- Mitchell RD, Prevalence of gastric ulcers in hunter/jumper and dressage horses evaluated for poor performance, Proceedings of Association of Equine Sports Medicine Conference, Sept 2001
- Boswell RP, Mitchell RD, Dyson SJ (2003) Lameness in the Show Hunter and Show Jumper. In: Diagnosis and Management of Lameness in the Horse, Eds, Ross M and Dyson SJ, Saunders, Philadelphia, pp 951-975
- Dyson SJ, The swollen limb. In: Diagnosis and Management of Lameness in the Horse, Eds, Ross M and Dyson SJ, Saunders, Philadelphia, (2003) 150-151
About the Author
Richard D. Mitchell, DVM, DACVSMR
Richard D. Mitchell, DVM, DACVSMR is a 1974 graduate of the Oklahoma State University College of Veterinary Medicine and is a senior associate at Fairfield Equine Associates in Newtown, CT and Wellington, FL. He has been internationally certified in veterinary acupuncture (IVAS) and equine locomotor pathology (ISELP), is a certified Radiation Safety Officer, and he completed requirements for Diplomate status in the American College of Veterinary Sports Medicine and Rehabilitation (ACVSMR) in 2015. Rick served as an official veterinarian to the US Equestrian Team at six Olympic Games between 1992 and 2016. He has a particular interest in lameness diagnostics and imaging. Rick was recognized as a distinguished life member of the American Association of Equine Practitioners and as a distinguished alumnus of Oklahoma State College of Veterinary Medicine in 2022.