Cruciate ligament injury is the most common cause of hind limb problems in dogs and unfortunately, around 50% of dogs develop this condition in both hind legs.

There are two ligaments (cruciate ligaments) within the knee that help to stabilise the joint whilst walking.  One of these ligaments is prone to tearing, either through injury or slow degeneration (weakening and inflammation).

Once the ligament has torn, the knee becomes unstable and inflamed.  This can result in structures within the joint commonly becoming damaged as the bones grind together in an abnormal fashion.

Walking becomes very painful and the thigh muscles rapidly waste away through reduced use.  If left untreated, severe arthritis can also set in, rendering the joint uncomfortable for many years to come.

What happens when it is damaged?

The cruciate ligaments help to stabilise the knee and prevent it from moving in certain directions.  Damage to these ligaments causes abnormal joint movement, overloading and damage to other structures, for example the menisci, which are tough cartilage pads that sit within the knee joint and act as shock absorbers to help to distribute weight evenly across the joint and help to add stability.

Consequently, failure of a cruciate ligament causes abnormal wear and tear, instability, lameness and pain in the affected knee joint.  Both short and long–term, it also causes osteoarthritis, which will need management.

Why does the cruciate ligament fail?

There are two main causes:

1. Degenerative disease (common)

This is the most common cause of cruciate ligament failure.  Dogs that are affected by this disease will have diseased, inflamed and weakened ligaments that will tear during normal activity, such as playing in the garden.

There can be several factors that can predispose a dog to suffer this disease and it is thought that breed has the most influence.   Certain breeds are known to be more at risk than others as there is a suspected genetic element, for example, in Golden Retrievers, West Highland Terriers, Rottweilers, Bull Mastiffs, Labrador Retrievers, Boxers and Newfoundland breeds.

Furthermore, some body conformations (bone structure) also predispose the ligament to rupture; for example, those with bowed hind legs or an upright posture.

Also, dogs carrying excess weight are also more at risk of this disease, which is another reason for maintaining your dog’s healthy weight (speak to one of our vets or nurses for advice about the optimal weight for your pet).

2. Trauma (rare form)

Overloading of a healthy cruciate ligament due to a sudden injury to the knee can cause damage and even rupture of the ligament.  This is the equivalent of cruciate injury in people where a normal ligament is damaged through playing sport.

How is it diagnosed?

Cruciate ligament failure can be diagnosed by history and clinical examination alone.  However, diagnostic tools such as MRI, arthroscopy (key-hole surgery) and radiography (x-rays) may also be needed to assess the joint fully.

What treatment can be given?

The knee joint needs to be stabilised to help reduce pain and try to prevent further damage to the internal structures.  This is generally achieved through surgery, but occasionally for small dogs and cats, we may opt for conservative (non-surgical) treatment, i.e. strict rest.  This decision will depend upon individual circumstances and will be discussed with your normal veterinary surgeon and/or referral vet.  It must be noted that whatever treatment is decided upon, we are treating a damaged or diseased joint and full 100% recovery is not expected, with our aim being 85-95% recovery which is sufficient for most pet dogs.

Conservative treatment will involve restricting their exercise, ensuring they stay at lean bodyweight, administration of pain relief and include ‘complementary therapy’ such as hydrotherapy and physiotherapy. This can be discussed on a case by case basis with your veterinary surgeon or animal physiotherapist.

The majority of dogs that are affected by this condition require surgery.  This can all be managed by either your normal veterinary surgeon that has an interest in orthopaedic (joint and bone) surgery or by one of our consultant orthopaedic surgeons at our Glenfield Referral Hospital.

What does surgery entail?

Surgery aims to stabilise the knee joint and prevent abnormal movement.  There are lots of different techniques that can be used to treat cruciate ligament disease.  The specific technique that might be recommended for your pet will depend on many factors and will be discussed with you by your normal veterinary surgeon and/or one of the consultant surgeons. The choice of which technique can depend on numerous factors ranging from patient size to available budget.

Overall, two general options are available when considering surgery.  The first involves placing a temporary (leader-line) or semi-permanent (Tightrope) implant, which stabilises the joint until the normal scar tissue forms to hold the joint in place.

The second option involves remodelling the shin bone to change the forces within the knee joint.  The shin bone (tibia) is cut (osteotomy) to shift the weight bearing dynamics within the joint.

We offer two methods, either a Tibial Plateau Levelling Osteotomy (TPLO) or a Cranial Closing Wedge Ostectomy (CCWO). Both techniques are proven in effectiveness but generally a TPLO is preferable as it is prone to fewer complications.  Both techniques try to address an underlying cause of ligament rupture: moving the top of the shin bone counteracts the forces present in the knee whilst walking.

Although these techniques are more invasive, recent studies have demonstrated that progression of osteoarthritis is reduced and the recovery period is shortened.

How long will it take my dog to recover?

Following surgery, it can take up to 4 months for full recovery and get back to their old self and activity levels again. For the first 8 weeks following surgery, their activity will be severely restricted (e.g. no jumping up, going up stairs or running around), and they will only be allowed outside on a lead to go to the toilet.

Once everything looks good on their check-ups/x-rays, you will then be advised to steadily build up their activity levels, and by 3-4months post-op, they could be back to their old antics and enjoying their favourite walks.

What are the long-term implications?

Long-term, it’s essential that you keep your pet active and in lean body condition to reduce the effects of secondary problems, such as osteoarthritis, never mind the myriad of other problems that arise from being overweight!

Also, in around one in twenty cases, the shock absorber cartilage pads within the joint may suffer an injury/tear over the next 12 months and further surgery might be required (termed a ‘Late Meniscal Injury’).

Dependent upon your dog’s breed, the same condition can happen to the other knee over the next 12-18 months.