A 5 year old dog presented with a hind limb lameness Acutely developing firm soft tissue swelling centering on the stifle joint was evident at this time The study was made one year following a stifle joint surgery that was thought to be successful in repair of a cranial cruciate ligament disease A radiographic study was made of the affected joint Radiographs of the affected stifle joint Radiographic findings
- The metallic implants secondary to the TTA procedure were noted to be as expected without evidence of loosening or breaking
- No evidence of bony lesion suggesting bony infection or reactive periosteal response was noted
- The discrete bony defect in the tibia plateau cranially represented the incomplete healing of the osteotomy site
- The bony lysis caudal and proximal to the femoral condyles was noted but not thought important
- The tibia plateau was noted to be displaced cranially and the patella was noted to be displaced cranially
- Changes suggesting further development of arthrosis that could be the cause of the lameness were not evident
- Radiographic quality was altered to permit better evaluation of the soft tissues
Radiographs for soft tissue
- Closer evaluation showed the soft tissue mass, a part of which was protruding into the stifle joint cranially while another part of the mass caused cranial displacement of the patella
- These studies suggest that the bone lysis in the distal femur was probably real and could be associated with an expanding soft tissue tumor
Pathologic diagnosis
- Soft tissue masses adjacent or within the elbow or stifle joint with suspect areas of bony lysis are highly suggestive of invasion by synovial cell sarcomas or histiocytic sarcomas
- The histopathologic diagnosis between the two tumor groups may not be clear
Study of a similar case presented in October 2008 in the stifle joint of a 10 year old male flat coated retriever – in this patient the bony lesions were in the tibia plateau and the distal femur just proximal to the patellar groove – it was diagnosed as a histiocytic sarcoma
