Lameness Conditions
Lameness is the most common cause of poor performance and retirement of the athletic horse, and as such occupies much of any clinician’s time as well as the pre-purchase examination. Lameness is a manifestation of signs of inflammation, such as pain, or a mechanical defect that results in a gait abnormality characterised by limping. Although the definition of lameness is simple, recognition, localisation, characterisation, and management may be complex. As such, the examination of the lame horse is performed in a methodical, step-by-step systematic approach. However, occasionally some components have to be avoided, for example in horses presented for acute severe lameness compatible with fracture, or due to financial constraints.
Components of lameness examination
- General and particular history of the horse
- Clinical examination
- Gait evaluation
- Diagnostic analgesia (nerve blocks)
- Imaging
- Diagnosis
- Therapeutic plan
- Follow-up examination
The first step of the lameness examination involves obtaining a detailed history from the owner regarding the current problem as well as any previous incidents. It is important to know when the current problem begun, what action has been taken and what effect if any it had. How is the lameness manifested, is it currently better or worse, is it changing with rest and/or work, is it responding to pain relief. What is the shoeing history of the horse and has anything changed? Was the horse lame before, on which leg and why.
Next visual appraisal of the horse is made, observing the horse from a distant and all four directions, including assessment of balance, conformation, muscle symmetry, evidence of external trauma etc. This is followed by detailed palpation of the neck, back, pelvis and all four limbs assessing for swelling heat and pain in various anatomical structures. Finally hoof testers are used to assess any sensitivity in the feet.
The stage of assessing the horse’s gait takes place next. The horse is walked and trotted in a straight line and then trotted in a circle, both on a soft as well as hard surface. Occasionally the horse will be asked to canter, and in rare cases the veterinarian will ask to see the horse ridden. The lame leg is identified in each gait and the lameness is scored. Part of this examination includes the flexion tests, whereby each leg is held in flexion for a short duration in order to assess any affect it may have on the degree of lameness.
Once the lame leg is identified, isolation of the area in the leg that is responsible for the lameness is made. This is most commonly achieved with the use of nerve blocks, whereby starting at the bottom of the leg and working up, a variable volume of local anaesthetic solution is injected into different anatomical sites alongside specific nerves, and after awhile the lameness is assessed for any change. Commonly, synovial structures such as joints or tendon sheaths (synovial sleeves surrounding tendons) may be locally injected as well in order to specifically identify the source of pain. In some instances the veterinarian may choose to avoid some blocks or not perform them altogether. Prior to any injection the hair is clipped and the skin is scrubbed with surgical antiseptic solution to minimise the risk of introducing contamination, especially into synovial structures.
Identifying the actual cause of the lameness can be made, in most cases, by imaging of the site the lameness was isolated to. Multiple imaging modalities are available at the Royal Veterinary College including: Digital Radiography (x-rays), Ultrasonography, Gamma Scintigraphy (bone scan), Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), and choosing the correct one depends upon many factors especially the information gathered in the examination thus far.
Once a diagnosis has been achieved a therapeutic plan can be made, and the veterinarian can now provide more specific information with regards to the longer term prognosis. Therapy can range from rest and controlled exercises, to medication or surgery. Cutting edge techniques including stem cell therapy are also available.