Anyone who watches sports, even if only occasionally, can see how devastating knee injuries are for star athletes.

Athletes who suffer from an ACL (Anterior Cruciate Ligament) injury are typically out for the rest of the season and must undergo knee surgery with a six- to eight-week recovery time following the operation.

Unfortunately, this is also one of the most common injuries for dogs and just as devastating.

The ACL is one of two bands of fibrous tissues located in the knee joint. The other fibrous band is called the posterior cruciate ligament.

These fibrous ligaments join the femur and tibia (the bones above and below the knee joint) so the knee works as a hinged joint. The cruciate ligaments cross over inside the joint. One ligament connects from inside to outside the knee joint and the other outside to inside, crossing each other in the middle. The ligaments allow the knee to bend up and down while preventing the knee from sliding back and forth.

Large breed dogs and overweight dogs are more prone to ACL injuries.

Traumatic cruciate damage is often caused by a twisting injury to the knee joint. The injury in dogs occurs in the same fashion as in human athletes.

Most often injury occurs when the athlete or dog is running and suddenly changes direction so the majority of weight is taken on this single joint.

Another common scenario is when a dog jumps down from an elevation two or three feet high. When landing, their legs (including the knee joint) become stationary as their body weight continues forward causing injury to the cruciate ligament inside the knee joint.

The ACL is usually the one affected since it is located in the front of the knee joint. The ligament may become stretched, partially torn or completely ruptured. The joint is then unstable and causes extreme pain.

The symptom of lameness is usually directly related to the severity of the injury. A stretched ligament may present as a more chronic form of cruciate damage because of gradual weakening of the ligament.

Diagnosis can sometimes be very difficult unless there is an history of the dog running and suddenly stopping or crying out in pain and then being unable to bear weight on the affected leg.

Another common situation that occurs and makes diagnosis difficult is when an owner assumes their dog has just sprained a joint and then waits several days or weeks to have them examined.

Scar tissue may develop allowing the joint to appear somewhat stable. During examination, a veterinarian will try to demonstrate a particular movement in the joint called a drawer sign. This laxity in the knee joint supports a diagnosis of a torn ACL. Many dogs will require some sedation before this test can be performed.

Having X-rays taken is also a good idea. Although the ligaments will not show up on an X-ray, small bone chips may be present because of the ligament trauma pulling off a piece of bone in the joint.

Any ligament damage inside of a joint will also initiate the process of arthritis and potential degenerative joint disease.

Inside the knee joint are pieces of cartilage called the menisci. The menisci act as shock absorbers between the femur and tibia. tThese cartilages are also commonly damaged when the cruciate ligaments rupture. They are usually repaired at the same time as the cruciate ligament surgery.

Surgery is certainly the best way to treat any dog suffering from a torn ACL.

Occasionally, a dog weighing less than approximately 20 pounds may heal without surgery by restricting them to cage rest for four to six weeks.

Unfortunately, most dogs will require surgery to repair this extremely painful and devastating injury.

There are several surgical techniques used to replace the action of the cruciate ligaments. Each of the surgical procedures have their pros and cons.

Personally, I prefer to perform a surgery that involves the placement of artificial ligaments along the outside of the knee joint. I have had great success with this surgical procedure for many years.

Regardless of surgical technique, post-operative care is important. Dogs should have limited activity for six to eight weeks after surgery. If you carry out your veterinarian’s instructions, good function should return to the leg within about three months.

Despite surgery to stabilize the joint, arthritis in the joint is inevitable. Weight control and medications such as glucosamines or joint supplements may help delay the onset of arthritis in your pet. Some dogs may require physical therapy to speed their recovery and reduce complications.

Therefore, if your dog starts limping or favoring one of his legs, contact your veterinarian as soon as possible to ensure your dog lives a long, healthy and happy life.

Dr. Jeff Castle is a veterinarian at Clark County Veterinary Clinic.