The lame cat, without a history of trauma can represent a diagnostic challenge. Factors that may contribute to this include a generalised lack of awareness of orthopaedic disease in this species and the fact that gait analysis and complete orthopaedic examination, which are necessary to detect subtle abnormalities, are difficult to perform in the cat.

History

The history may not be as helpful for cats as it is for dogs; clinical history taking must be tailored to determine subtle changes to normal behaviour. Mildly injured cats frequently do not exhibit obvious or specific clinical signs and the onset of these signs is often insidious making them even more difficult to appreciate. Outdoor cats spend a lot of time unobserved by their owners, with general habits including urination, defaecation and grooming often not being seen for days at a time. Even with trauma, the traumatic event itself is rarely seen.

Overt lameness is uncommon in cats. Presentations that have been associated with joint disease and discomfort include stiffness, a shuffling gait, difficulty jumping, weakness, inactivity, reduced grooming, altered temperament and inappropriate elimination habits. While questions are often constructed to identify a decrease in activity, orthopaedic disease often causes alterations in inactive behaviours in cats and this should also be investigated.

Environment Modification and General Handling

Physical examination can be complicated by the fractious nature of some cats but it remains important wherever possible to perform this in a consistent and structured manner. As for dogs, a full general physical examination should precede the orthopaedic examination.

A quiet and calm environment should be provided; ideally, cat-specific waiting rooms and consulting rooms should be employed. Over-restraint should be avoided as this can lead to aggression or alternatively a cat that is immobilised by fear. If it is impossible to examine the cat without restraint, sedation may be preferable to mechanical restraint, particularly for lengthy or painful procedures. For less amenable patients, it is quite common for the author to perform a brief orthopaedic examination, sufficient to localise the source of pain with the cat conscious, followed by a detailed examination under sedation at the same time as performing further diagnostic tests. Scruffing should be avoided where possible as it is painful, particularly in older and heavier cats. Where it is necessary, the weight of the cat should always be supported from the bottom while scruffing to control the head. For cats which are very stressed by the hospital environment, it can be useful to ask owners to administer a dose of gabapentin prior to bringing the cat to the hospital - this can produce a calming effect rendering them more likely to tolerate examination. Synthetic cat pheromones sprayed on towels or used in the area may also assist.

Gait Assessment

Gait assessment can be difficult and time consuming as most cats will not walk on a lead and often refuse to move around a new environment. Positioning the cat in the centre of the room but within sight of a corner or basket will often result in the cat moving towards the hiding place allowing gait observation. Assessing the ability to jump up and down from elevated areas in the consulting room can be useful. A cat with pelvic limb problems is more likely to have difficulty jumping up while a cat with thoracic limb pathology will likely be reluctant to jump down or may land awkwardly. Some cats will play with the spotlight of a laser pointer or with their favourite toys so it can be worth asking owners to bring these in. If the cat will only walk a very short distance, videotaping this and playing it on a loop can make subtle gait abnormalities more obvious. Alternatively, if the cat will not walk in the consulting room at all, asking the owner to videotape the gait at home and bring this to the consultation can be helpful.

Many cats, when nervous in a consulting room, will walk with a crouched pelvic limb stance, so this should not be over-interpreted unless it correlates with findings on physical examination such as bilateral hip discomfort, spinal pain or patellar luxation. An attempt should be made to grade the lameness as this will assist with monitoring progression after treatment.

However, as it is often not possible to observe more than a few steps at a time, grading on a scale of 1–10 or 1–5 as is often performed in dogs can be difficult. An alternative grading scheme of 1–3 has been proposed which the author finds practical.¹

 Grade 1 - Low-grade lameness: Lameness is hardly visible or there is no lameness visible but the cat lifts the foot when sitting (thoracic limbs) or is unable to jump (pelvic limbs).

 Grade 2 - Medium-grade lameness: Lameness is clearly visible but the limb is used with most steps. A noticeable head-bob maybe evident or for unilateral pelvic limb lameness the tail may be used to shift weight toward the sound side.

 Grade 3 - High-grade lameness: The cat is only toe-touching or not weightbearing at all.

Cats with bilateral orthopaedic problems may not show a distinct lameness but are inactive and reluctant to jump, sometimes sitting or standing with an abnormal posture or walking with a crouched gait. Bilateral orthopaedic disease of the thoracic limbs is less common than that of the pelvic limbs but can result in a shuffling gait.

Physical Examination

Similarly to in dogs, the cat should initially be examined in a standing position; this facilitates direct comparison between limbs and detection of asymmetry. The shoulder, back and thigh musculature can be palpated and assessed for evidence of muscle atrophy or differences in tone. The bony protuberances are compared on each side to assess for asymmetry as would be present with coxofemoral luxation or scapular avulsion. The musculature along the spine should be palpated gently and the range of motion of the neck assessed. Many cats react to palpation along the lower back and adverse reactions should be interpreted with caution as they are often not clinically significant. Weight-bearing asymmetry can be assessed at this stage as well as conscious proprioception as in dogs.

With the cat in lateral recumbency, all the limbs are systemically examined. Remember that bite wounds are the most common cause of lameness in the cat and should be suspected in every lame cat with access to other cats; there is normally evidence of marked cellulitis, soft tissue swelling and a severe pain response upon palpation. Examination starts with application of gentle pressure over all of the bones looking for deviations, pain, temperature changes and swelling followed by manipulations of all of the joints looking for crepitus, swelling, periarticular thickening, increases or decreases in the range of motion (ROM) and pain.

It is important to know the approximate normal ROM of the joints and to be aware that feline joints are generally more elastic than canine joints. The normal flexion and extension angles for the carpus, elbow, shoulder, tarsus, stifle and hip have been published, as well as the varus and valgus angles of the carpi and tarsi² but these can vary widely between individuals and therefore comparing the ROM to the contralateral joint is recommended for diagnosing cases with minor instability. Avoid firm grasping of the lower back, tail or feet as this often leads to defensive behaviour. Unfortunately, joint thickening, synovial effusion, reduced ROM and crepitus are far less obvious in the cat when compared to the dog.³ The skin, muscles and tendons are also evaluated including the nails, nailbeds and footpads. Special attention should be paid to the common calcaneal tendon, the patellar tendon and the tendon of the triceps muscle as rupture of these structures has been described.

Generally, it is recommended that manipulations that are anticipated to be painful are performed at the end of the examination; however, it is important to recognise the temperament of the individual patient. If only a limited window of opportunity for examination is likely to exist, manipulation of the area considered likely to be affected on the affected limb may have to be performed earlier to ensure examination of this area is covered before the time window expires. Assessing a pain response in a sedated patient is very difficult and therefore pain response is the one aspect of the examination which must be completed during conscious examination if possible. If the cat becomes aggressive and uncooperative during examination, there is little point in persisting, and hospitalising the patient for another attempt later may be the best route forward.³

Following a complete history, gait assessment and orthopaedic examination, localisation of the cause of the lameness should be possible. This can then be used to direct further diagnostics and treatment strategies, or, where conservative management is elected, can be used as a baseline upon which to assess treatment efficacy at the next visit.

References

1.  Voss K, Steffen F. Patient assessment. In: Feline Orthopaedic Surgery and Musculoskeletal Disease. Elsevier London; 2009:3–19.

2.  Jaeger G, Marcellin-Little D, DePuy V, et al. Validity of goniometric joint measurements in cats. Am J Vet Res. 2007;68:822–826.

3.  Bennett D, Zainal Ariffin SM, Johnston P. Osteoarthritis in the cat: 1. How common is it and how easy to recognise? J Feline Med Surg. 2012;14:65–75.