RADIOGRAPHIC EVALUATION OF FELINE APPENDICULAR DEGENERATIVE JOINT DISEASE VS. MACROSCOPIC APPEARANCE OF ARTICULAR CARTILAGE MILA FREIRE,IAN ROBERTSON,HOWARD D. BONDELL,JAMES BROWN,JON HASH,ANTHONY P. PEASE, B. DUNCAN X. LASCELLES Degenerative joint disease (DJD) is common in domesticated cats. Our purpose was to describe how radio- graphic findings thought to indicate feline DJD relate to macroscopic cartilage degeneration in appendicular joints. Thirty adult cats euthanized for reasons unrelated to this study were evaluated. Orthogonal digital radiographs of the elbow, tarsus, stifle, and coxofemoral joints were evaluated for the presence of DJD. The same joints were dissected for visual inspection of changes indicative of DJD and macroscopic cartilage damage was graded using a Total Cartilage Damage Score. When considering all joints, there was statistically sig- nificant fair correlation between cartilage damage and the presence of osteophytes and joint-associated min- eralizations, and the subjective radiographic DJD score. Most correlations were statistically significant when looking at the different joints individually, but only the correlation between the presence of osteophytes and the subjective radiographic DJD score with the presence of cartilage damage in the elbow and coxofemoral joints had a value above 0.4 (moderate correlation). The joints most likely to have cartilage damage without ra- diographic evidence of DJD are the stifle (71% of radiographically normal joints) followed by the coxofemoral joint (57%), elbow (57%), and tarsal joint (46%). Our data support radiographic findings not relating well to cartilage degeneration, and that other modalities should be evaluated to aid in making a diagnosis of feline DJD. r 2011 Veterinary Radiology & Ultrasound, Vol. 52, No. 3, 2011, pp 239–247. Key words: cartilage damage, cat, DJD, macroscopic, radiographs. Introduction F ELINE DEGENERATIVE JOINT disease (DJD) is common in domesticated cats. 1–5 The high prevalence has gener- ated interest in describing the clinical signs, evaluating causes and predisposing factors, and measuring the pain associated with the radiographic changes. 6–12 Despite this interest, there is no information on how the radiographic findings of feline DJD relate to actual degeneration of the various joint components, such as cartilage. Grading of DJD in animals and human patients is usu- ally performed using radiographic imaging and evaluation of cartilage changes during surgery or arthroscopy. How- ever, the usefulness of various radiographic features of DJD for prediction of articular cartilage degeneration is not well documented in any species. In humans, marginal osteophytes may be the most sensitive radiographic feature for the detection of articular cartilage degeneration in the patellofemoral joint. 13,14 Historically, radiographic criteria used to assess canine DJD have been applied to cats 2–4 and it has been assumed that these criteria are indicative of joint tissue degenera- tion. However, some have suggested that the radiographic features of DJD in the cat are different to those in the dog. 5 Others have suggested that cats do not form osteophytes as readily as dogs 2,3,5,10 ; while still others have suggested ra- diographically normal joints can be a source of pain due to DJD. 3,8 Clearly, there is a need to understand how the radiographic features of feline DJD relate to joint tissue degeneration. High-resolution analog radiographs have increased spa- tial resolution compared with digital radiographs. Al- though digital radiographs have poorer spatial resolution, considered important in feline orthopedic imaging, the as- sociated enhanced dynamic range and postprocessing ca- pabilities can lead to an overall improvement in diagnostic performance. 15 There are no studies comparing analog vs. digital imaging systems with respect to feline extremities. Funding was provided by Novartis Animal Health, through their global Fellowship Research program. This study was completed at the North Carolina State University Col- lege of Veterinary Medicine, Raleigh, NC. Address correspondence and reprint requests to B. Duncan X. Lascelles at the above address. E-mail: duncan_lascelles@ncsu.edu Received June 27, 2010; accepted for publication January 18, 2011. doi: 10.1111/j.1740-8261.2011.01803.x From the College of Veterinary Medicine, 4700 Hillsborough St., Ra- leigh, NC 27606 (Freire, Robertson, Brown, Hash, Pease, Lascelles); De- partment of Statistics, North Carolina State University, Box 8203, Raleigh, NC 27695 (Bondell). 239