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CHAPTER 7 ARTHROLOGY

Feline arthrology has been an overlooked subject in term osteoarthritis is reserved for the specific type of the past with most reviews of joint disease in small DJD that affects diarthrodial synovial articulations. animals focusing on the dog. However, cats are now Diseases of synovial joints can conveniently be known to suffer from many different types of joint divided into degenerative arthritis and inflammatory disease and, although there are many similarities with arthritis on the basis of the predominant pathologic the dog, there are also many features that are unique process (Table 20). Degenerative are the to the feline patient. most common types and include traumatic arthritis and osteoarthritis. Inflammatory arthropathies are less CLASSIFICATION OF JOINT DISEASE common than degenerative arthropathies and have The terms arthritis and literally mean joint either an infective or immune-mediated etiology. inflammation and joint disease, respectively. These terms Infective arthritis caused by bacterial infection (septic are used interchangeably in this chapter to describe arthritis) is the commonest type of inflammatory arthritis a number of well defined joint diseases characterized in the cat. Septic arthritis is classed as an erosive type of by a combination of inflammatory and degenerative arthritis because there is destruction of articular cartilage changes. The terms degenerative joint disease (DJD) in joints infected by bacteria. Immune-mediated and osteoarthritis are also often used synonymously. In arthropathies can be subdivided into both erosive this chapter, DJD is used as a general descriptive term to and nonerosive forms. Differentiation between the encompass degenerative changes in any joint in the infective and immune-mediated forms of inflammatory axial or appendicular skeleton, including synovial, arthritis is essential since the therapeutic approaches cartilaginous, and fibrous types. When DJD affects the to these conditions are diametrically opposed. fibrocartilaginous intervertebral joints of the spine, it is Inappropriate treatment of an infective arthritis with known as spondylosis deformans (see Chapter 11). The immunosuppressive drugs will have disastrous results.

TABLE 20 CLASSIFICATION OF JOINT DISEASE. Degenerative Inflammatory Miscellaneous arthritides arthritides joint disorders Infective Immune-mediated Synovial Osteoarthritis arthritides arthritides Secondary neoplasia Traumatic Primary Bacterial (septic) Systemic lupus erythematosus Hypervitmainosis A arthritis Secondary Bacterial L-form Polyarthritis/meningitis Mycoplasmal Idiopathic Synovial osteochondromatosis Calicivirus Periosteal proliferative Synovial cysts Lyme disease Rheumatoid Patellar malformation Tubercular Meniscal calcification Fungal Osteochondritis dissecans in the Scottish Fold cat Ch07 final.qxd 7/2/07 13:55 Page 88

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INVESTIGATION OF JOINT DISEASE then to stop interpreting the radiograph before the occurs with erosive immune-mediated or infective example joint sprain, whereas thickening is a SYNOVIOCENTESIS whole film has been assessed. All three components of arthritides, osteomyelitis, and joint neoplasia. chronic change most often associated with joint For details of synoviocentesis and analysis of synovial the joint should be evaluated radiographically: the Localized areas of sclerosis and remodeling of the instability, such as chronic cranial cruciate fluid see Chapter 2. bones, the soft tissues, and the joint space. The specific subchondral plate may be seen at the margins of ligament (CrCL) rupture. It is not possible to features that should be examined are the bony anatomic destructive lesions, such as osteomyelitis. differentiate between thickening and swelling RADIOGRAPHY relationships, subchondral bone plates and subchondral However, sclerosis is more commonly seen as a radiographically. Mineralization of periarticular Radiography is the most frequently used ancillary bone of the epiphyses, the width and contents of the generalized change in chronic osteoarthritic joints tissue is a rare occurrence. It is occasionally seen diagnostic aid in the investigation of joint disease. joint space, the articular margins and periarticular where there is loss of articular cartilage and as a sequela to chronic inflammation, for example Radiographs should be interpreted in the light of the regions, and the periarticular soft tissues. The eburnation of the opposing joint surfaces. bacterial infective arthritis, and is also a feature of clinical findings and not used as a substitute for a radiographic appearance of some disorders that are • The subchondral bone of the synovial osteochondromatosis. correctly performed clinical examination. Radiography familiar to the canine clinician may differ in the cat. For subadjacent to the subchondral plate should have is usually used to confirm a suspected clinical diagnosis example, the predominant radiographic signs of feline a homogenous appearance. In comparison with Contrast arthrography or to differentiate between two or more joint diseases hip dysplasia are a shallow acetabulum with remodeling the dog, the cancellous bone of cats has a coarse Contrast arthrography is rarely performed in the cat. that have similar clinical characteristics. However, of the craniodorsal margin but with minimal trabecular pattern. Osteomyelitis, neoplasia, and Positive contrast arthrography involves the injection of radiographic surveys of multiple joints might be remodeling of the femoral neck (55)1. articular fracture will cause an alteration in the a contrast agent into a joint space so that it mixes with indicated to evaluate the overall status of the patient in • The anatomic relationships of the bones making internal architecture of the trabecular bone. the synovial fluid and delineates the internal margins of conditions that are frequently polyarticular, such up the joint may be altered with joint luxation, Subchondral cysts are occasionally seen in the joint. The contrast agent of choice is iohexol as osteoarthritis or immune-mediated arthritis. subluxation, and intraarticular fracture. Reference osteoarthritic joints in cats as discrete radiolucent (Omnipaque 300; Nycomed), which is diluted 50:50 Radiographs of other body regions may be indicated; to a radiographic atlas, a file of normal cat defects in the subchondral bone. with sterile water to give a concentration of 150 mg of for example, in cats with joint trauma or neoplasia or radiographs, or a radiograph of the contralateral • Joint space width may be increased with joint iodine per ml. The technique is most useful for some of the immune-mediated arthritides to check for joint may be helpful, especially for the smaller subluxation or luxation. Narrowing of the joint investigation of shoulder joint pathology. The volume evidence of lesions elsewhere. more complex joints of the distal extremities. space is indicative of loss of articular cartilage but of contrast agent required for suspected articular Feline joints are small so it is essential to obtain high • The subchondral bone plate should appear as a cannot be appreciated on normal nonweight- cartilage lesions (0.5–1.0ml) is less than that required quality radiographs if they are to be of diagnostic value. thin radiopaque line parallel to and adjacent to bearing radiographs. to detect capsular defects or to outline the biceps Radiographs of joints should be correctly collimated to the joint space. Erosion of the subchondral plate • Joint space structures are contained between the tendon of origin (2.0–3.0ml). minimize scatter and obtained using fine detail screens subchondral bone plates of the opposing bones in two orthogonal planes (i.e. at right angles to that comprise the joint. This space, therefore, SONOGRAPHY each other). Human mammography film/screen includes the articular cartilage, synovial fluid, and Ultrasonography has potential value for the combinations are especially useful for radiographs of the 55 intracapsular fat (and intraarticular ligaments, investigation of joint disease but there are few reports distal extremities. Additional stress views may be menisci, and synovial effusion when present). of its use in cats3–5. The evaluation of bone is limited performed in the evaluation of joint instability. Oblique Intraarticular structures are only visible when they because of the inability of ultrasound to penetrate projections and special views to outline certain become mineralized2 or when increased joint mass osseous tissues. However, sonography may be useful structures are performed less frequently in the cat than results in distension of periarticular soft tissues or in the identification of joint effusion, joint in the dog. It is often useful to radiograph the alteration of other intraarticular structures. An thickening, articular or bone destruction, and joint contralateral joint to provide a normal radiograph for example of the latter would be a reduction in size instability using a dynamic examination. Periarticular comparison or because some conditions occur of the infrapatellar fat pad in the stifle, associated structures that may be examined with bilaterally. General anesthesia or heavy sedation is usually with a synovial effusion. Differentiation between ultrasound include muscles, tendons, abscesses, cysts, required for optimal positioning. increased joint mass associated with the presence foreign bodies, and tumors. Use of the technique is Radiographic interpretation must be thorough and of soft tissue or fluid cannot be made likely to remain restricted to specialized centers complete so that each structure is assessed according to radiographically and requires synoviocentesis. because of the small size of the structures under its Roentgen signs. Radiographic lesions in feline joint • The articular margins and the periarticular areas investigation and the difficulty in the interpretation disease are often subtle and the use of a magnifying where ligaments and tendons attach should have of the images obtained. glass and a bright light in addition to a normal viewer is a regular, smooth cortical outline. recommended. The radiologist should be familiar with generally develop at the articular margins where ARTHROSCOPY normal feline osteology and with the radiographic they appear as characteristic bony outgrowths. Arthroscopy is rarely used in the investigation and appearance of normal feline joints. Accessory centers of Osteophytes are most commonly associated with treatment of feline joint disease. Examination of the ossification and sesamoid bones may be present in or osteoarthritis. Osteophytes that develop at the shoulder and stifle joints is possible6,7 but so far there around joints and these ossicles should not be confused site of bony attachment of the joint capsule or at are mostly only anecdotal reports of its success. There with chip fractures. For example, an accessory center of ligament or tendon insertions are known as is one report of the successful evaluation and ossification may be present as a normal anatomic variant enthesiophytes. debridement of the elbow joints of a cat with in the shoulder joint on the caudal or medial rim of the 55 Ventrodorsal radiograph of the pelvis of a cat with • Periarticular soft tissues are assessed for swelling, intraarticular osteochondral fragments8. Application glenoid. Methodical examination is essential; the most coxofemoral osteoarthritis secondary to hip dysplasia. Note thickening, and mineralization. Swelling most of arthroscopy to other feline joints is likely to remain common error is to find the expected abnormality and the remodeling of the cranial margins of the acetabula. commonly occurs as a result of acute trauma, for limited because of their small size. Ch07 final.qxd 7/2/07 13:55 Page 90

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LABORATORY TESTS and disruption of articular cartilage. Intraarticular rediographed for any reason, 22% showed evidence of dystrophic calcification or synovial metaplasia. A minimum database for investigation of a suspected osseous and/or cartilage fractures are associated with osteoarthritis of an appendicular synovial joint, Degenerative enthesiopathy and intraarticular or inflammatory arthropathy would include a bio- the more severe traumatic injuries and may occur in although this was not clinically apparent in 67% of periarticular soft tissue mineralization often accompany chemistry and hematology panel and tests for feline isolation or combined with joint luxation or cases10. In another study of 100 cats over osteoarthritis, but may also occur independently. Other leukaemia virus (FeLV) and feline immunodeficiency subluxation. Following a traumatic incident there will 12 years of age, radiographic evidence of DJD was pathologic changes include thickening of the joint virus (FIV). This may help to identify cats that are be hemorrhage within the joint and , which found in 90% of cats and severe osteoarthritis was capsule, an increase in vascularity with hypertrophy and immunosuppressed or those that have involvement of may be localized to the site of injury. found in 17% of elbow joints11. The realization that hyperplasia of the lining layer of the synovial other body systems, such as may be seen with some osteoarthritis is a common clinical problem in the cat membrane, and degeneration of intraarticular menisci. immune-mediated arthritides, (systemic lupus Clinical signs is a relatively recent phenomenon12. The degeneration of articular cartilage that occurs in erythematosus and idiopathic polyarthritis types II, Clinical signs include lameness, joint swelling, joint osteoarthritis may be associated with the formation of III, and IV). Further investigation of joint disease deformity, and pain on manipulation. Crepitus will be Cause and pathogenesis osteocartilaginous bodies that remain free in the joint, requires synoviocentesis and synovial fluid analysis present if there is fracture or luxation. Osteoarthritis as a cause of chronic pain is common in disappear, or become embedded in the synovium. (see Chapter 2). Individual tests, such as measurement the geriatric cat, but it may be seen in any cat with joint Subchondral cysts are an occasional feature of of titers for rheumatoid factor, antinuclear antibody, Diagnosis abnormality or following injury. It is postulated that osteoarthritic joints in cats. A cyst develops when there or antibodies to Borrelia burgdorferi, may be indicated If fracture or luxation is suspected, radiography the inciting cause is repeated joint trauma associated is replacement of subchondral bony trabeculae by in appropriate circumstances. These tests are discussed should be performed. Joint instability and ligamentous with the cat’s agile life style and ability to jump. In mixed connective tissue. more fully with the relevant joint disorders. disruption are evaluated by manipulation under accordance with this theory, some studies have found general anesthesia and stress radiography. Injury to that the shoulder and elbow joints of geriatric cats are Clinical signs SYNOVIAL MEMBRANE BIOPSY individual ligaments is most commonly encountered in preferentially affected. Osteoarthritis may also be Osteoarthritis is an emerging disease of the older cat. Biopsy of the synovial membrane or synovium is rarely the stifle and tarsocrural joints. Joint sprains are secondary to gross trauma, such as joint fractures, Osteoarthritis has long been recognized performed in the cat. The procedure can provide an classified according to the severity of the ligamentous luxations, and ligamentous disruption. Developmental radiographically in cats but, because the disease may invaluable insight into the pathology affecting a joint injury as first, second, and third degree. diseases, such as hip dysplasia or patellar luxation, may be asymptomatic, the changes were often considered and is the only way of achieving a definitive diagnosis lead to osteoarthritis. Osteoarthritis has been reported incidental. The lack of attention to feline in some cases. Samples are usually collected by means Treatment and prognosis in multiple joints as part of feline mucopolysac- osteoarthritis may be explained by a tendency to of an arthrotomy and should be obtained from several A more detailed discussion of the treatment of charidosis VI13 and associated with acromegaly in extrapolate information from the dog where the different sites to ensure that the changes seen are traumatic disorders relating to specific joints can be middle-aged cats caused by a pituitary adenoma14. The cardinal sign of osteoarthritis is lameness. It is now representative of the pathologic process in the entire found in Chapters 8 and 9. In general, treatment pathogenesis of acromegalic arthropathy is not fully believed that behavioral changes reflecting chronic joint. of joint trauma depends on the severity of the injury. understood but it is thought that cartilage hypertrophy pain are more relevant to the diagnosis of The histologic appearance of feline and canine First degree sprains are mild and only require rest may interfere with cartilage metabolism, thereby osteoarthritis in the cat. Because cats are small, light, synovial membrane is similar9. Histopathologic and/or anti-inflammatory medication. Second and causing cartilage degeneration. and agile they compensate well for musculoskeletal examination can provide precise information about third degree sprains and more severe types of joint Despite multiple etiologies, the pathologic changes disease and are able to adapt by redistributing weight- the extent and type of cellular infiltrate, allowing injury such as intraarticular fracture usually require of osteoarthritis share a final common pathway bearing forces to other limbs. Additionally, because differentiation between degenerative and inflam- external coaptation or surgical repair. Osteoarthritis that serves to perpetuate the degenerative processes. the cat’s lifestyle prevents critical analysis of the gait by matory joint disease. Although there is considerable will occur as a sequela to traumatic arthritis if there are Attention usually focuses on the articular cartilage but, the owner, mild lameness or joint stiffness usually overlap between diseases, the nature of an inflam- repeated mild to moderate episodes or if a single typically, all of the joint structures are involved. passes unnoticed. Behavioral changes reported by matory cell infiltrate may help in determining the type episode is severe enough to cause significant damage to Cartilage becomes fibrillated and ultimately may be owners of cats with osteoarthritis are nonspecific and of inflammatory arthritis. Histopathology is the only the joint. completely lost, exposing the underlying subchondral include those associated with attitude (hides away, way of achieving a definitive diagnosis of joint bone, which responds by becoming thickened. The resents handling, bad tempered, less playful) and neoplasia. Samples of the synovium can also be OSTEOARTHRITIS other main feature of osteoarthritis is the production of those associated with disability (reduced grooming, submitted for bacterial culture and may be more likely Osteoarthritis is a type of DJD that is defined as a osteophytes, which initially develop outside the cannot jump, inactive). Lameness and stiffness to yield organisms than synovial fluid. disorder of diarthrodial synovial articulations epiphysis of the joint, but eventually become associated with osteoarthritis typically have an characterized by degeneration of articular cartilage, incorporated into the joint, so that the joint assumes a insidious onset and are chronic and progressive in DEGENERATIVE ARTHRITIDES bone remodeling, pathologic changes in periarticular different shape. This process is known as remodeling nature. As in other species, signs are worse on rising TRAUMATIC ARTHRITIS tissues, low-grade nonpurulent inflammation, and the and is thought to be a mechanism that allows the joint after a period of rest following exercise and initially Cause and pathogenesis formation of new bone at the articular margins. to cope better with the altered stresses placed on it. wear off after the animal warms up. The signs may Traumatic arthritis follows a single acute joint injury Osteoarthritis may be classified into primary and Osteophytes are usually thought of as a chronic change tend to wax and wane and are usually exacerbated by caused, for example, by vehicular trauma, an awkward secondary forms. Primary osteoarthritis is thought to in osteoarthritis, but they have been shown to start to cold and damp weather. Acute flare-ups of the signs of fall, gunshot wounds, or fights with other animals. occur as a consequence of an inherent defect in the develop within 1 week of experimental induction established osteoarthritis may occur as part of the The least severe form of injury is a joint sprain, in articular cartilage so that it is unable to cope with of joint instability15. Enthesiophytes are soft tissue natural history of the disease or be associated with which there is variable stretching or tearing of normal joint forces, whereas secondary osteoarthritis mineralizations that develop when there is pathology of joint sprain or sepsis. Osteoarthritic joints are ligaments and joint capsule. Joint luxation involves a is secondary to some other joint disorder. Most the entheses, which are osseous insertion sites of susceptible to trauma and are also at increased risk of more severe disruption of peri- and intraarticular osteoarthritis is thought to be secondary in the cat. In ligaments and tendons. Additional soft tissue infection spread hematogenously from a septic focus structures, with tearing of ligaments and joint capsule a recent retrospective study of cats over 1 year of age mineralization may occur as a result of capsular elsewhere in the body. Ch07 final.qxd 7/2/07 13:55 Page 92

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Diagnosis feature is the presence of osteophytes. These are normal or has only a slight reduction in viscosity and Weight loss is essential if the cat is obese and use of In advanced cases the diagnosis of osteoarthritis may visualized as roughening of the joint margins, as a minimal increase in cell numbers, with macrophages a commercial low-calorie diet is recommended. be obvious, especially if there is overt lameness. obvious bony masses (spurs or exostoses) projecting and lymphocytes predominating. Conversely, geriatric cats that are underweight should Affected joints will be thickened on palpation owing beyond the normal bony outline, or as irregular bony be fed a calorie-dense diet, since osteoarthritis will to bony remodeling, joint capsule fibrosis, and densities when superimposed on the normal osseous Treatment and prognosis worsen if they stop exercising as energy levels decline. synovial effusion. It is not usually possible to architecture. There will be secondary soft tissue The approach to the management of osteoarthritis in Pain control in cats with osteoarthritis has been a appreciate this in the shoulder and hip joints because swelling with thickening of the joint capsule and there the cat is similar to that for dogs. Options include problem in the past because of a lack of drugs of the surrounding soft tissues. Manipulation of a may be an increase in joint mass owing to synovial exercise modification, weight control, the use of specifically licensed for long-term use in the cat joint with osteoarthritis will usually be resented and effusion. Although enthesiophytes and/or soft tissue drugs, and surgical intervention. Potential problems (Table 21). Cats are more susceptible than other there may be crepitus and a reduced range of joint mineralizations are commonly seen in osteoarthritic with the management of osteoarthritis include lack of species to the adverse effects of nonsteroidal motion. The subtler behavioral changes associated joints, these features alone are not indicative of familiarity with the disease in cats, difficulties with antiinflammatory drugs (NSAIDs) because of a with osteoarthritis may be caused by many other osteoarthritis. With advanced osteoarthritis there will lifestyle modification, and the toxicity of available deficiency of glucuronide conjugation. Slower drug diseases, and careful assessment of the geriatric cat is be changes in bone shape due to remodeling, drug therapies. Despite this, the prognosis for metabolism and a longer half-life lead to accumulation required to establish their significance. This may accompanied by sclerosis of subchondral bone and, osteoarthritis is generally better than that for the dog of toxic amounts much faster in cats than other include radiographic and laboratory evaluation to occasionally, subchondral bone cysts visualized as because cats are smaller and more athletic. species16,17. Currently the only drugs for which safe confirm the presence of osteoarthritis and rule out discrete radiolucent defects. Modification of a cat’s exercise regimen may be chronic doses have been established by clinical usage intercurrent disease. Analysis of the synovial fluid from affected joints difficult but some control is possible; for example, by are aspirin and meloxicam. Even with these drugs it is The radiographic changes of osteoarthritis are can be performed to rule out inflammatory joint altering the environment or by only allowing the essential that dosing is performed accurately if similar to those of the dog (56). The most striking disease. The fluid from joints with osteoarthritis is cat out at set times each day. Strategies used in the dog, toxic effects are to be avoided18,19. Aspirin is such as restricted leash exercise and aquatic therapy, are only available in human formulation and it is not sometimes appropriate for the cat. Lameness associated commonly used in the cat for the treatment of 56 with flare-ups of osteoarthritis should be managed by osteoarthritis. Meloxicam is available in an injectable enforcing strict confinement for a few days. form and as a syrup, which is palatable to cats and

TABLE 21 ORALLY ADMINISTERED DRUGS AND NUTRACEUTICALS USED IN THE MANAGEMENT OF OSTEOARTHRITIS. Drug Dose (mg/kg) Dose (5 kg/cat) Remarks Meloxicam 0.1 mg/kg once daily 5 drops once daily Suspension is 1.5 mg/ml suspension for 5 days then for 5 days then 1–2 palatable 0.02–0.04 mg/kg drops once daily C Tolfenamic acid 4mg/kg 20mg once daily Do not exceed 20mg tablet 3 days’ use Ketoprofen 1mg/kg 5mg once daily Do not exceed 5mg tablet 5 days’ use Flunixin 1mg/kg 5mg once daily Do not exceed meglumine 5mg tablet 3 days’ use Aspirin 15mg/kg 75mg every May cause 75mg & 300mg tablets 48 hours gastrointestinal side-effects Prednisolone 0.1–0.5mg/kg 0.5–2.5mg once Taper to every 1mg & 5mg tablets or twice daily 48 hours Butorphanol 0.5–1mg/kg 2.5–5.0mg two Sedative side-effects 5mg tablets or three times daily Cosequin 1 capsule once Contains glucosamine, regular strength daily for 6 weeks chondroitin sulphate, A B D then once daily glycosaminoglycans, 56 Osteoarthritis. A Plantarodorsal radiograph of a cat with osteoarthritis of the hock joint secondary to previous trauma. or 1 every 48 hours manganese ascorbate B Plantarodorsal view of the contralateral normal hock joint. C Mediolateral radiograph of a cat with osteoarthritis of the elbow. D Craniocaudal view of the joint in C.