A torn ACL is the most common knee injury experienced by dogs. This can happen suddenly or through time, but either option can be quite excruciating.
How a Torn ACL Occurs
Your dog's knee has three bones: the femur extending from the hip, the tibia extending from the ankle and the patella (knee cap). These bones are held together by ligaments, which prevent the bones from rubbing against each other, quite a painful experience.
The ACL (anterior cruciate ligament) is the ligament that holds the femur and the tibia together from the front of the knee. It is most commonly torn on the back leg but can be torn on any leg.
If your dog tore his ACL suddenly, it most likely happened during play or excited activity. This is usually caused by your dog's leg twisting suddenly in a way that the ACL can't withstand. This could also happen if your dog suffered severe trauma, like falling off a building or being hit by a car. Thus, you may suspect an ACL tear if you recently noticed your dog suffer an accident or begin limping after play.
It's harder to detect a torn ACL if it has degenerated through time since the symptoms may increase gradually, making them more difficult to notice or appear similar to arthritis. If your dog is overweight, this increases the likelihood of a torn ACL.
Checking for a Torn ACL
The most common symptom of a torn ACL is sudden lameness in the injured leg. Your dog will not want to put pressure on the leg at all, causing obvious limping and reluctance to participate in activities that your dog used to enjoy.
The other easily recognized symptom is a swollen knee, which will appear large but will cause your dog pain to the touch.
In small dogs, a luxating patella may lead to a torn ACL. These symptoms include sudden pain in your dog as his knee becomes popped out of joint. This is often short-lived as your dog will pop the knee back in place and often appear fine after a few hours. Consult your veterinarian when this happens.
In larger dogs, particularly if they are overweight, you may notice an increase in limping through time or the limping may be pronounced sometimes and non-existence at other times. You also may notice that your dog sticks his leg out to the side when sitting rather than tucking it underneath his rear for a standard sit.
Diagnosis and Treatment of a Torn ACL
To diagnose the injury, your veterinarian will likely simply examine the knee joints by placing his hands on them and feeling the movement. This will usually alert him of an injury. If not, an additional X-ray may be required.
Just as with humans, treatment usually involves surgery. Afterward, your dog will be on bed rest for several months, allowing the ligament to properly heal.
If your dog is overweight, it's important to reduce his weight during his recovery so he doesn't suffer from the same injury again.