Cranial cruciate ligament (CCL) injury is very common in dogs, but rare in cats. This ligament is in the dog and cat’s knee and it runs from the femur (thigh bone) to the tibia (shin bone). In humans it is called the Anterior Cruciate Ligament or ACL. The ligament is one of the main forward-backward stabilisers in the knee. This means in essence that the CCL stops the tibia moving forwards relative to the femur, almost causing the femur to fall of the back of the tibia.
Cranial cruciate ligament injuries: how do they occur?
Most CCLs are injured due to slow degeneration in the ligament. Fibres in the ligament weaken over time, often resulting in complete failure. To date we do not know exactly what causes the weakening. Some evidence suggests genetic factors, although obesity, individual developmental conformation, hormone changes and inflammation of the knee joint may all play a contributing role. Whatever the cause, the final result is the same: a weakened ligament that is snapped with the slightest tension – even just a normal step.
Cranial cruciate ligament disease: what are the symptoms?
Most dogs show limping or lameness. This limping can be in many forms, from occasional limping (this is often as the ligament is weakened, stretches and partly frays) to limping so badly that the dog does not even want to place the foot on the ground at all (often just after it snaps completely). But any limping to any degree in the back legs could be associated with injury of the CCL.
How is CCL disease diagnosed?
The main test is by feeling for excessive movement between the femur and tibia. This can be very tricky to do in some big dogs and often requires sedation. It can also be very difficult to diagnose in the early stages of the disease and is best evaluated by a vet experienced in CCL injury diagnosis. X-rays can help in the diagnosis, especially in early disease, but is rarely required to make a diagnosis. It does help to estimate the extent of arthritis, which can have implication on treatment options.
There are three options when it comes to treatment of CCL injury. And each of these will be discussed separately below. The options are conservative non-surgical management, surgery where the ligament is replaced, and surgery that makes the CCL unnecessary. Each treatment option has pros and cons. And it is essential to understand that there is not just a single treatment that suits every dog, or one that is right in every case. Multiple factors are considered when treatment options are discussed.
1. Non-surgical Management
Non-surgical management is very seldom recommended as our surgical options can be so successful. But at times the risk of anaesthesia, age or other diseases (such as a patient with renal failure) may make non-surgical management the only option. Management here would include weight reduction, exercise modification, physiotherapy and medication (anti-inflammatories and pain killers). Dogs weighing more than 12 – 15 kg are unlikely to return to full function. Knee braces can also help and can be recommended in the right circumstances. Braces are, however, very expensive, sometimes as expensive as surgery.
2. Ligament Replacement Surgery
There are quite a few ligament replacement techniques and they have been used for many years. At Cottage Vet we use what is called an Extracapsular Nylon Imbrication technique. A nylon band is placed from the femur to the tibia, in order to stabilise the knee joint.
This sounds great, but there are quite a few limitations. The nylon band mimics the actual ligament, but the CCL is quite a complex ligament, and cannot be 100% accurately replaced. The nylon band can also snap or stretch, particularly in big dogs. So, we do not generally recommend this treatment for dogs over 15 kg, nor for very active dogs (such as Staffies). This surgery is generally more cost effective than other surgeries and is better than no surgery at all, but it is important to understand the possible complications with this type of surgery so discuss these with your vet.
3. Surgery that renders the Cranial Cruciate Ligament redundant
These surgeries developed due to the limitations and complications seen with ligament replacement techniques. There are again a few procedures that can be performed, all with the aim of changing the mechanics of the knee is such a way that the CCL is no longer needed. All of these procedures require that the tibia is cut to some degree and all have some risks associated with them, but they do have much better clinical outcomes than either conservative or ligament replacement surgeries.
4. Tibial Tuberosity Advancement
Tibial Tuberosity Advancement (TTA) is a procedure where the front portion of the tibia is cut and moved more forward and kept in place in a variety of ways. This changes the way that the muscles and other ligaments (particularly the thigh muscles) pull on the tibia, thereby eliminating the need for the CCL. At Cottage Vet Dr Morné is experienced in performing tibial advancement by the Modified Marquette Procedure (MMP).
The MMP uses a wedge-shaped pure titanium implant called OrthoFoam. This allows for accurate advancement and rigid fixation, with quick ingrowth of new bone. The advantages of the MMP is that is allows for the quickest recovery of all surgical procedures (generally just 4 weeks) and is naturally resistant to infection. It is one of the best procedures to consider for big and athletic dogs but can be done in any size dog. Most dogs can return to full athletic function, which means they can run and jump and play as much as they want.
4. Tibial Plateau Levelling Osteotomy (TPLO)
During this procedure the tibia is completely transected with a circular cut. The top of the tibia is levelled and fixed in a place with a plate. Thus, the femur is “balanced” on the tibia and the CCL is not longer needed. It is also indicated in large dogs but is often very costly and recovery can take longer than a TTA/MMP.
5. MMP vs TPLO
There is considerable debate amongst academics which of the two procedures are better. Multiple studies have tried to see if one procedure is superior to the other, and to be honest – the jury is still out. Some studies have found some differences both ways, but the result remains the same. Both procedures work, both procedures result in clinical improvement and both procedures have pros and cons. There is not a single procedure that is right for all patients in all situations. So careful consideration and consultation with your veterinary surgeon is important to see which procedure is right for you and your pet.
Cranial Cruciate Ligament injury is extremely common and can be treated in a number of ways. If your pet is limping, be sure to book an appointment with one of our vets as soon as possible. Dr Morné has successfully operated on hundreds of dogs with this type of injury.