Dog's nagging knee injury is frustrating

9/9/2012

Dear Dr. Thompson: My 5-year-old lab had surgery for a torn ACL in her knee in February where heavy-duty suture was used to stabilize the knee. She started limping badly about two months ago. My veterinarian has X-rayed her and felt her knee but isn't sure why she is limping. She is starting to lose a lot of muscle in her thigh since she started limping again. What options do I have?

I am sorry to hear that she is limping again after surgery, but the scenario you describe typically means one of a limited number of reasons for the change in her condition. Since she is a lab, I assume she is a larger dog and the type of surgery you describe — called a lateral suture — can occasionally fail. The suture will stretch or break and lead to instability in the knee, which is manifested by limping. If the suture has broken down, it may be necessary to replace the suture or perform another type of surgery called a TTA or TPLO, which are generally a better choice for larger dogs.

If the suture is not the culprit, it may be the cartilage shock absorber inside the knee joint called a meniscus. This cupped ring of cartilage is frequently torn when dogs tear the cruciate ligament. A meniscal tear is very painful and a small percentage of dogs may develop one in the first few months after surgery. Many dogs with a small tear will do well with rest and time, but if she hasn't improved over the past couple of months a second surgery to evaluate the inside of the knee joint will be needed. Relatively speaking, it is a less invasive surgery and most dogs are significantly improved a couple weeks after the operation.

The third possibility would be an infection in the knee joint or around the suture material. The suture is not the type that dissolves over time and if bacteria are able to get onto the implant, it can be difficult to clear. Less commonly, an infection can smolder inside the knee joint and lead to pain and swelling a couple months after surgery. Collecting some of the fluid from inside the knee to be evaluated is the first step. If infection is present, often the only solution is to go back in to remove the implant material. If the knee joint is stable, that may be all that is needed. However, if instability is still present in the knee another surgery would be necessary.

I understand how frustrating it can be after a long recovery to have her limping again, but with a little investigation you should be able to get to the source of the trouble. Many times the solution is much simpler than the original surgery. Good luck.

Questions for Dr. Gary Thompson can be emailed to askthevet@theblade.com or mailed to The Blade, Attn. Ask the Vet, 541 N. Superior St., Toledo, OH 43660. Dr. Thompson regrets that he cannot answer individual letters.