The cranial cruciate ligament (CCL) (also referred to as the anterior cruciate ligament in people), is a tough, fibrous band found within the knee. This ligament attaches the femur (thigh bone) to the tibia (shin bone) and in doing so provides stability of the knee joint. We often hear of cruciate injury causing career threatening injury in our top sports stars, with it being a particularly common footballer’s injury. A bad tackle for example may cause the ligament to rupture and this is solely down to excessive trauma. The situation in our dogs is quite different and acute trauma is rarely the cause of CCL injury, but rather degeneration of the ligament over time, somewhat akin to the fraying of a rope. We don’t know the precise cause of degenerative CCL disease but genetic factors play a role, with certain breeds being predisposed (including Labradors, Rottweilers, Boxers, West Highland White Terriers and NewFoundlands). The genetic influence also leads to many dogs suffering CCL disease in both hind legs, often while still relatively young. Other factors also play a role such as obesity, individual conformation, hormonal imbalances and certain inflammatory conditions of the joint.
Diagram of a dog’s knee joint showing the cruciate ligaments.
Hindlimb lameness is the most common sign of CCL injury. This can either be sudden onset after exercise, or more gradual and progressive in nature. In some unlucky individuals both legs are affected at the same time leading to a dog that has great difficulty rising from rest and has a pottery gait.
In dogs with CCL disease a number of important changes are occurring in the joint:
- Osteoarthritis is present at the earliest stage (as a result of inflammatory processes brought about by fraying of the ligament) and results in painful lameness.
- The femur will roll back on the tibia every time the affected leg weight bears (this leads to mechanical lameness” and is a result of the loss of the mechanical stabilising function of the CCL).
- In some dogs where mechanical instability exists, other joint structures become subject to trauma and can be damaged (in particular a pair of joint cartilages, called menisci, can be crushed and torn by the femur slipping back down the slope of the tibia).
Diagnosis of CCL disease is normally by a combination of physical examination (whereby the joint is manipulated to check for the characteristic mechanical instability) and also radiographic changes. Normally a dog will need to be anaesthetised for this to be carried out thoroughly. For the majority of dogs diagnosed with CCL rupture, surgery will be recommended. Exceptions to this would be rare and generally involve those animals where the risk of anaesthetic or surgery is deemed too high. Dogs over 15kg have a very poor chance of ever using the leg properly without surgical intervention. Medical management in small dogs and cats is more favourable than for the larger dogs, but still involves a rehabilitation period of many months and is rarely a complete recovery.
There are a few options for the surgical management of CCL disease or rupture:
- Ligament replacement techniques
- Treatments which render the CCL redundant
- Libial Plateau Levelling Osteotomy (TPLO)
- Tibial Tuberosity Advancement (TTA)
- Modified Maquet Procedure (MMP)
The latter three treatments involve re-alignment of bone. Because bone healing is far more efficient than ligament healing, these are generally considered more robust than surgeries designed to replace the damaged ligament. The vast majority of dogs return to normal activity, with the owners unable to detect lameness at home, after the TPLO, TTA and MMP techniques.
This month’s case study looks at CCL using the MMP technique. As a practical aside, some insurance policy’s offer injury only cover – most of these will not cover cruciate rupture, even when seemingly sudden onset after an event on a walk, as it is considered a degenerative condition. A good reason to always check the small print when choosing an insurance policy!
Case Study : Cruciate surgery
Kai is a bouncy Springer Spaniel who recently turned 5 years old and has not had the best year. At the start of 2015 he had a sore leg, and after a week of painkillers and rest he was no better so investigations began.
This is Kai looking healthy and happy after his second surgery.
X-rays and an exam under sedation showed that he had ruptured his cranial cruciate ligament. This is one of the most common orthopaedic problems we see in dogs and usually needs surgery to manage it.
The following week he was admitted for surgery to have a new technique called a Modified Maquet Procedure (MMP) to address his sore leg. This involved cutting part of his shin bone – just below his knee – and moving it forwards. A special titanium wedge is used to advance this part of the bone forwards, and it is stabilised with a stainless steel pin and a titanium staple. This advancement of the bone changes the way the knee works so it can cope fine without the ruptured cruciate ligament.
A special titanium wedge is used to advance this part of the bone forwards, and it is stabilised with a stainless steel pin and a titanium staple.
Kai was discharged with painkillers and joint supplements. These supplements will now be given to Kai for the rest of his life as arthritis will still form even after the surgery. Joint supplements help to slow down the progression of the arthritis and can give some additional pain relief.
Now the hard part for Kai began – 6 weeks of strict cage rest! To allow the bone to heal and grow into the titanium wedge Kai had to have his exercise restricted and controlled. Kai – like most Springer Spaniels – doesn’t enjoy rest! However, his humans followed our advice as rest is such an important part of the recovery process.
At the 6 week mark we took follow up x-rays to confirm everything was going as expected – and it was. Everything was healing and Kai was already using his leg without any lameness. So he was allowed to go on some short leash walks. Amazingly by the 12 week point he was back to his usual bouncy, happy (and pain free) self!
However, Kai was back at the end of 2015 showing very similar signs in his other hind leg. His second surgery has been a huge success and once again his follow up x-rays are showing a fantastic recovery.