Further Diagnostic Techniques 1
Radiography
The image shows the effects of increased joint fluid production on the soft tissues around the joint. These are non specific changes that do not definitively diagnose CCL pathology. We may also see evidence of Degenerative Joint Disease (DJD) and the extent of these changes will be influenced by chronicity and to some extent breed.
Radiograph showing reduction in Infrapatellar Fat pad and deviation of the caudal fascial plane secondary to increased Synovial fluid volume (effusion)
As with most orthopaedic radiography, positioning and correct exposure is essential to pick up these often subtle radiographic features. Over flexion of the stifle for example as in the image below will often reduce the appearance of the signs of effusion noted above. In the top case, the reduction in Infrapatellar shadow can be seen but the caudal fascial plane distortion is absent. Whilst the second radiograph obscures all meaningful information.
The 90 degrees of flexion seen here will often obscure the signs of effusion
This extreme flexion eliminates almost all meaningful information regarding synovial fluid volume.
This radiograph shows cranial tibial translation indicative of CCL rupture
Recommendation
The position of the stifle becomes even more critical in cases where TTA is planned. In general the current recommendation is that the stifle should be positioned in extension. This is not the often quoted 135 degrees but whatever represents the normal standing angle of the patient’s stifle. The third radiograph above whilst diagnostic of CCLR should not be used for templating for TTA as the tibia is already in a pathologically advanced position. This will reduce the accuracy of the required advancement for the procedure.
The craniocaudal view is less important in terms of diagnosing CCL pathology but is an essential view to rule out other pathologies that may result in effusion such as Femoral condylar osteochondrosis dissecans and neoplastic processes.
Conclusion
Essentially all effusion indicates is Active Joint Pathology. When this appearance is combined with appropriate history and patient age and breed, it may point in the direction of CCL pathology but is not Diagnostic.
Coming next… Synovial Aspiration and Palpation.