1
Subjective Gait Evaluation

Felix Michael Duerr

Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO, USA

1.1 Introduction

Lameness can be due to orthopedic, oncologic, or neurologic conditions that disrupt the tissues responsible for normal locomotion. Subjective gait analysis is one component of the orthopedic and neurologic examination and provides valuable information to assist in determining what limb(s) and structures are affected. Succeeding chapters further discuss the other components that play an important role in any canine lameness evaluation (e.g. history, orthopedic examination, etc.).

1.2 Observation at Rest

Subjective gait evaluation starts by observing the animal at rest, when it stands, or raises from a sitting or lying position. Frequently, this can be accomplished by letting the animal roam freely in the exam room during the history taking. During this time, the observer may also evaluate mental status, behavior, and posture of the patient (which is part of the neurologic exam, see Chapter 4). Many dogs will show obvious off-loading of the affected limb during standing (Video 1.1), particularly with cranial cruciate ligament disease and neurogenic (i.e. nerve root signature) lameness. Caution should be used when interpreting off-loading if the animal is not standing square. Anxious animals may be encouraged to stand still by leading them toward an exit door, pausing prior to opening the door. Most dogs will focus on the door being opened and while being distracted, the observer can judge weight-bearing in a square position.

Video 1.1:

Pelvic limb lameness - unilateral CCLD.

Difficulty in either rising, or sitting, or both suggests a problem in the hind end. For example, animals with cranial cruciate ligament disease will display a classic sitting pattern avoiding flexion of the affected stifle(s). Animals that sit "square" (Chapters 19 and 20; Video 20.2) are unlikely to suffer from cruciate disease. Animals with lumbosacral disease may have difficulty rising, while animals with bilateral cruciate disease will hesitate to sit down. Spontaneous knuckling (i.e. standing on the dorsum of their paw during stance) indicates neurologic disease.

1.3 Observation in Motion

During the subjective gait evaluation, the observer is attempting to localize and specify the type of lameness (e.g. which leg is most severely affected, neurologic versus orthopedic origin, etc.). Certain gait features, such as ataxia or dragging/scuffing of the toes, clearly indicate neurologic disease. Decreased range of motion in a joint and the associated gait changes may point toward an articular source of the lameness. Changes in stride length may indicate a musculoskeletal or neurologic problem. Increased range of motion may indicate a ligament problem (such as carpal hyperextension injury with increased carpal extension or Achilles tendon rupture with increased tarsal flexion).

The use of slow-motion video analysis for improving the observer's ability to identify a lameness has been reported in dogs and horses; however, no clinical benefit was observed in a recent canine study using dogs (He Lane et al. 2015). Although in that study the degree of lameness was not quantified. Nonetheless, in the author's experience, this technique can be extremely helpful in dogs with a subtle lameness (Video 1.2). Slow-motion videography is integrated into newer smart phone devices and numerous apps also offer this feature, thus making it easily utilized in daily practice.

Video 1.2:

Thoracic limb lameness - case examples.

1.3.1 Presentation

Ideally, the animal is presented by a dedicated handler/technician. Since most owners are not used to walking their dog without interfering with gait, this approach will allow reducing the time required to complete the lameness evaluation: the handler should allow the animal to move freely (e.g. not pulling on the leash) yet at a constant speed. Pulling on the leash makes observation of a head nod more difficult. Ideally, the animal should look straight ahead during evaluation. This can be accomplished by letting the animal walk toward the owner.

The animal should be observed at the walk and ideally at the trot if the severity of the lameness allows. In general, if animals are unable to trot, their disease should be severe enough that lameness identification can be done at a stance or walk. A flat, even surface with good traction, such as a parking lot or driveway, is ideal to avoid distractions (such as areas to sniff/mark). The gait should be viewed both from the side (to judge stride length, symmetry, and possible changes in sagittal joint range of motion) and the animal moving toward and away from the examiner (to judge head nod, pelvic tilt, and frontal plane abnormalities).

To make a lameness more detectable, the animal can be asked to trot in circles, walk stairs, go up and down hills, or perform the tasks that trigger an impaired gait or movement (e.g. such as jumping for agility dogs). For example, animals with thoracic limb disease will display a more pronounced head nod when going downstairs and will use the non-affected limb to step down first. Animals with hip dysplasia will show simultaneous advancement of the pelvic limbs (i.e. "bunny hopping") when going upstairs. Subjective gait evaluation generally is performed prior to manipulation; however, sometimes manipulation may worsen the lameness.

1.3.2 Gait Patterns

To allow the clinician appropriate evaluation of gait, an understanding of normal gait patterns is essential. Gait patterns are generally described by their beat, whether they have a suspension phase and whether they are lateral or diagonal gait patterns. The beat describes the number of ground impacts within each stride cycle (i.e. the walk is a four-beat gait because each limb touches the ground at different time points within the stride cycle). The suspension phase describes a phase where none of the feet are touching the ground, which is observed only in gaits with a high velocity like the trot and canter. The description of diagonal versus lateral gait describes which limb pair is supporting the animal's weight (i.e. a diagonal gait indicates that the diagonal limb pairs move simultaneously such as when trotting; whereas, in a lateral gait, the ipsilateral limb pairs move simultaneously such as when pacing). For detailed online descriptions of the footfall patterns and slow-motion animations, consult Datt and Fletcher (2012).

The dog's ambulatory motion has been described to consist of up to seven different gait patterns: walk, trot, pace, amble, canter, transverse and rotary gallop (Leach et al. 1977; Datt and Fletcher 2012). The walk is a four-beat gait without a suspension phase. The amble is an accelerated walk, maintaining the four-beat gait pattern. The trot is a two-beat, diagonal gait with suspension phase. The pace is a two-beat, lateral gait in which ipsilateral limb pairs move in synchrony (Figure 1.1 and Video 1.3). The canter is an asymmetric gait (i.e. a three-beat gait with different patterns on the right and left side). The gallop is the fastest gait. While there has been controversy whether the pace is a normal or abnormal gait, it has been described to be used by dogs without obvious orthopedic disease. Proposed reasons for dogs to pace include orthopedic pathology, tiring, confirmation such as proportionally long legs, or an acquired gait due to being forced to walk at speeds between the walk and trot (Wendland et al. 2016). Particularly if a dog switches from a regular walk to pacing, evaluation for any change in orthopedic status is indicated. However, while pacing as the only symptom (i.e. without obvious lameness) may be an early indicator of musculoskeletal disease, it should not be considered pathologic by itself. Regardless, it is important for the clinician to assess whether a dog uses the pace.

Video 1.3:

Trotting versus pacing.

Another important reason to understand gait patterns is to allow for interpretation of compensation patterns for lameness such as head nod or pelvic tilt. The trot is the most steady and rhythmic gait and therefore generally the easiest gait to identify a mild-moderate lameness. Interpretation of lameness becomes more complicated in animals that are pacing. As such, if the animal can be discouraged from pacing by choosing a different velocity (e.g. by having the handler increasing speed, see Video 1.3), this may simplify the subjective gait analysis.

Figure 1.1 Simplification of the footfall patterns of the pace. The pace is a symmetrical lateral gait, meaning that ipsilateral limb pairs move simultaneously. Black paw prints represent thoracic limb feet and grey paw prints represent pelvic limb feet.

1.3.3 Head Nod and Pelvic Tilt

To unload a painful limb, animals use specific adaptive strategies to reduce pain associated with weight-bearing. This is accomplished by shifting weight toward the unaffected limb(s), changes in joint angles,...