Twenty-five cats in each age group were successfully recruited and included in the study. Of the 100 cats recruited, 18 were purebred, and 82 were domestic shorthaired or longhaired. The mean (± SD) age was 9.42 ± 5.07 years (range, 6 months to 20 years), and mean bodyweight was 5.13 ± 1.64 kg. (range, 2.08-10.16 kg). The median (range) body condition score (BCS) was 3 (1-5) out of 5. The temperament scores were 0 in 40% of the cats, 1 (18%), 2 (13%), 3 (24%), or 4 (5%). Due to this fact, incomplete pain scores were present in 8-15% of individual joints and spinal segments for a total of 207 missing pain scores out of 2000. Conscious goniometry could not be performed in 28 cats due to their temperament, but goniometry was performed in all cats when sedated. Radiographic assessment was complete in every cat.
The prevalence of radiographic DJD in this population has been described previously [10
]. The number of affected joints, or spinal segments and associated manipulation scores for pain, crepitus, effusion and thickening (SPain
respectively), as well as the number of joints with no abnormalities apparent on examination, are summarized in Table . The elbow and hip joints were most frequently found to be painful, followed by the stifle and tarsus. The lumbar and lumbo-sacral (L-S) segments were the most frequently painful segments in the axial skeleton. The elbow joint most frequently had an elevated SC
, and ST
, followed by the stifle and tarsus. Cats with unfriendly temperament (scores 3-4 inclusive) had higher radiographic DJD (P
= 0.005 and pain scores (P
= 0.028) than cats with friendly temperament (scores 0-2 inclusive).
Number of joints (percentage) with radiographic DJD, pain on manipulation, crepitus, effusion, or thickening among 100 cats.
There were significant associations between radiographic DJD and pain scores, which held true for the right and left elbows (P < 0.002) and the lumbar and L-S region (P < 0.032) when collapsed DJDN/Y and PainN/Y were used in the analyses. There were significant associations between DJDN/Y and normal/abnormal SC, SE, ST, for both elbows (P < 0.002) and tarsi (P < 0.03) with the exception of the right tarsus SC (P = 0.054) and left elbow SE (P = 0.536). The SENS, SPEC, PPV, and NPV of normal/abnormal SC, SE, ST, values and PainN/Y with regards to DJDN/Y are listed in Table . SENS was low overall, and was highest for PainN/Y. PPV was highest for SC and ST but was generally low. SPEC and NPV were higher, suggesting that the absence of orthopedic examination findings of pain, crepitus, effusion and thickening could be used to rule out DJD with a high degree of certainty. The overlap of radiographic and orthopedic findings is listed in Table .
Sensitivity, specificity, and predictive values (%) of orthopedic examination findings for the detection of DJD in 100 cats.
Numbers of joints and spinal segments with DJD on radiographs, pain on palpation, and with both among 100 cats
ROMC and ROMS differed significantly for the stifle joints, right shoulder and right carpus, although the differences were small, ranging from 1° to 5° (Table ). ROMS data were collected more rapidly than ROMC data (median, 17 min; range, 9-27 min vs. 25 min and 10-40 min, P < 0.0001).
Mean (range) maximal range of motion (ROM) measured in cats when conscious (C-Max) and sedated (Sed-Max)
The odds ratios indicated that higher SC, SE, ST, and SPain increased the likelihood of a joint having DJD present (Table ). For example, cats with positive SPain in the right elbow were 5.5 times more likely to have DJD compared to cats with negative SPain. Similar increases were present for the left elbow, the lumbar, and lumbo-sacral areas. The likelihood of a joint having DJD was also increased for joints with positive SC, SE, and ST, particularly for the elbows and tarsi. Larger ROMC in shoulders, elbows and tarsi were associated with a lower likelihood of there being DJD present (P < 0.028) Larger ROMS in elbows, shoulders, carpi, and tarsi was associated with a lower likelihood of there being DJD present (P < 0.025).
Influence of orthopedic examination findings on the likelihood (odds ratios) of there being radiographic DJD present in 100 cats.
Age had a large effect (> 10% change in odds ratios) on the relationship of SPain, SC, SE, and ST, and DJDN/Y. Weight, sex, temperament, and time point during the study had a minor effect (< 10% change in Odds ratios). BCS had a variable effect, but on average it was < 10% for all parameters, and it did not change the significance of the relationship between the parameter and DJD. For the appendicular skeleton, controlling for age decreased the likelihood that a joint with a positive orthopedic parameter (pain, crepitus, effusion, thickening) had radiographic DJD by between 28 and 37% (average changes: appendicular pain, -28%; crepitus, -29%; effusion -36%; thickening, -37%). This effect resulted in a change in significance (Table ). Study time point (data collected in the first 4.5 months of the study compared to data collected in the second 4.5 months of the study) had the next largest effect on ORs for SE (11% increase on average) but not on other OR; however significance was not altered. For the axial skeleton, controlling for age decreased the likelihood that a positive pain response would be associated with radiographic DJD by between 3 and 76% (cervical, -76%; thoracic -3%; lumbar -42%; lumbo-sacral, -58%; average axial, -45%), and this resulted in a loss of significance for the lumbar and lumbo-sacral segments. When an interaction term was included in the model to evaluate OR, age was not shown to be an effect modifier, and stratification analysis supported this conclusion. Age had no confounding effect on the association between an abnormal ROMC or ROMS and the likelihood of a joint having DJD.