Cruciate Ligament Disease
Rupture Of The Cranial Cruciate Ligament
What is the cranial cruciate ligament?
The cranial cruciate ligament in dogs is the same as the “anterior” cruciate ligament in humans. It is a band of tough fibrous tissue, which attaches the femur (thigh bone) to the tibia (shin bone), preventing the tibia from shifting forward (cranially) relative to the femur. It also helps to prevent the knee joint from over-extending or rotating.
What happens when the cranial cruciate ligament ruptures?
The main effect of a cranial cruciate ligament rupture is laxity (i.e. looseness) of the knee, with the tibia tending to shift forward relative to the femur when the dog stands on the leg (known as “tibial thrust”). This causes discomfort (e.g. as the soft tissues around the knee are stretched), inflammation and development of osteoarthritis. The cartilage within the joint may also become eroded, including tearing of the menisci (cartilage shock-absorbing pads within the knee).
Why does the ligament rupture?
Much as in humans (especially footballers and golfers), it is possible for dogs to damage their cruciate ligaments by “trauma”, such as by sudden twisting or over-extension of the knee. However, this is extremely rare as a sole cause in dogs and usually only occurs in very athletic dogs (e.g. working sheep dogs).
In the vast majority of dogs, the cranial cruciate ligament ruptures as a result of long-term degeneration, whereby the fibres within the ligament weaken over time. We do not know the precise cause of this, but genetic factors are probably most important, with certain breeds being predisposed (including Labradors, Rottweilers, Boxers, West Highland White Terriers and Newfoundlands). Other factors such as obesity, individual conformation (i.e. shape of legs), hormonal imbalance and certain infections may also play a role.
Will my dog develop osteoarthritis?
As soon as cranial cruciate ligament degeneration starts to develop, osteoarthritis (inflammation of the joint and associated bones) immediately starts to develop too. Once present, osteoarthritis cannot be cured, but in most patients, it can be effectively managed.
What are the symptoms of cranial cruciate ligament rupture?
Hind limb lameness is the most common presenting symptom. Swelling and obvious instability (such as a clicking noise when the dog walks) are also identified in some dogs, particularly if the cruciate ligament is fully ruptured at the time of diagnosis. Many dogs are reluctant to bend the affected knee, so when they sit, the affected leg may stick out to the side of their body instead of being bent under their hind-quarters.
Many dogs will have degenerative changes of the cranial cruciate ligament in both knees. In this circumstance, lameness may be less obvious, but affected dogs may appear stiff, reluctant to exercise or play, or may seem generally depressed. This is sometimes erroneously perceived as a different problem, such as a spinal or hip issue.
How is cranial cruciate ligament rupture diagnosed?
Diagnosis in dogs with complete rupture of the cranial cruciate ligament is usually based on examination by an experienced orthopaedic surgeon, with demonstration of laxity of the joint by specific manipulations of the knee. In dogs with partial tears or early degeneration of the ligament, other tests may be necessary, including X-rays. In most dogs, exploratory surgery or arthroscopy (keyhole surgery) is used to confirm the diagnosis, and to investigate for possible cartilage tears or other diseases.
Various treatment options are available. The best treatment option for each dog can only be recommended following thorough assessment including the degree of laxity/looseness of the knee, patient size and lifestyle, and conformation (limb shape). The cruciate ligament itself is unable to heal once it is damaged, so treatment is focused on stabilizing the knee joint in the absence of a cranial cruciate ligament.
What are the treatment options?
Non-surgical management is seldom recommended, except where the risks of a general anaesthetic or surgery are considered excessive (e.g. patients with severe heart disease, uncontrolled hormonal disorders or immune conditions, etc.)
In this circumstance, four basic methods are usually recommended:
Body weight management
Exercise modification, including hydrotherapy
Anti-inflammatory / pain relief medications
Nutraceutical supplements (e.g. glucosamine, chondroitin sulphate, pentosan polysulphate, Green-lipped Mussel extract)
The knee may eventually stabilize by formation of fibrous scar tissue around the knee although this may take many months or even years in many patients.
2.Surgical ligament replacement
Over the last 30 years, a number of techniques have been developed, aimed at replacing the cranial cruciate ligament either with the dog’s own tissues or with a synthetic ligament prosthesis. Where this method is required, we prefer to use a recently-developed material known as Fiberwire® (Arthrex, Naples, FL, USA) which is mechanically superior to the commercially available alternatives, and has been shown to be effective in a large number of clinical cases. A system has been developed to allow placement of the Fiberwire® around the outside of the joint so that it closely mimics the function of the cruciate ligament.
3.Mechanical osteotomy procedures
Over more recent years, several techniques have been developed which change the mechanics of the knee joint such that the joint becomes stable in the absence of a functional cranial cruciate ligament. These procedures rely on cutting the tibia (shin bone) and fixing it in a new position in such a way that the load-bearing and muscle forces on the knee are balanced, neutralising tendency for the shin bone to shift relative to the thigh bone.
We use two major techniques (dependent on individual anatomy, conformation and presence of other diseases):
- Tibial Plateau Levelling Osteotomy (TPLO)
- Cranial Closing Wedge
Although these techniques are slightly more complex, patients may actually recover more quickly than with some ligament replacement techniques, with use of the operated leg within 1-2 days, and resolution of visible lameness within a few weeks.