Dear Dr. John,
Our mixed breed dog has always been nervous ever since we adopted her a few years ago. Late last year she came up lame on her right rear leg. After not improving for a few weeks, we had our vet look at her and he diagnosed that she had a torn cruciate ligament based on the physical examination. We were surprised that it did not take more like an x-ray to make the proper assessment.
We were referred to an orthopedic surgery specialist and our dog had a procedure done called a TPLO. She healed quickly and all was fine. However, about two months ago, we noticed a small red swelling on the inside of the same knee joint, so our vet placed her on antibiotics for two weeks since it appeared to possibly be an infection. He suggested it could be a draining lesion from the surgery. When it did not resolve, he referred us back to the surgeon. The original plate in the leg was removed, antibiotics were given, and a culture was done that showed no infection. Does all of this make sense? S.M.
Dear S.M.,
Your dog sustained a ruptured anterior (cranial) cruciate ligament from what you describe. Since she is a nervous dog, I wonder if she jumped suddenly or made an abrupt movement that might have caused the tearing of the ligament. Your veterinarian made a diagnosis probably based on the presence of an anterior drawer sign and/or a medial buttress which is a bony deposit on the inside of the knee joint.
Radiographs are often done to confirm the diagnosis. The TPLO surgery is a tibial plateau leveling osteotomy that saws bone and places a metal plate and screws providing support for a new angulation of bones in the joint. While not common, and even less so in orthopedics, post-surgical infections can occur. I suspect that the presentation that you observed was a draining tract.
Since the culture came back as negative, it’s likely that either the first course of antibiotics treated the possible infection sufficiently or the draining lesion was possibly due to instability of the metallic implants.
Dr. John de Jong is President of the World Veterinary Association. He owns and operates the Boston Mobile Veterinary Clinic and can be reached at 781-899-9994.