Cruciate Disease in Dogs
Written by Shula Berg BVSc CertAVP(GSAS) GPAdvCert(SASTS) MRCVS
Clinically reviewed by Elizabeth McLennan-Green BVM&S CertAVP(SAM) MRCVS
Table of Contents
Cruciate disease refers to partial or complete rupture of the cranial cruciate ligament. This ligament attaches the femur (thigh bone) to the tibia (shin bone) inside the stifle (knee joint). It helps hold the two bones in relation to each other during standing and walking. If the cranial cruciate ligament is damaged the femur slide backwards in relation to the tibia during weight-bearing, which is uncomfortable.
In humans, rupture of the cruciate ligament is almost always a traumatic injury. In dogs, it is generally a chronic degenerative process. In young, active dogs, the ligament may appear to “pop” suddenly (such as while running around), but it is likely there was already an underlying weakness present.
The primary symptom of cruciate rupture is limping on the affected hind leg. In most patients, this limp appears suddenly, and is such that the leg is not used at all.
As cruciate disease is usually a degenerative process, sometimes the ligament becomes gradually weaker, which may be seen as an intermittent limp or stiffness. If this happens over a long period of time, scar tissue develops which tries to support the joint. When the ligament finally ruptures, we may see that the lameness worsens but the leg is still used. In these cases, there is often muscle loss in the affected limb, meaning the thigh looks thinner than on the opposite side.
Often, we have a high index of suspicion of cruciate disease due to the dog’s breed, age and history. The key finding to confirm a diagnosis of cranial cruciate ligament rupture is instability of the stifle (knee joint). In some dogs, this may be felt while they are awake, however, most patients counteract the instability by tensing their muscles, so a definitive diagnosis is made under anaesthesia.
X-rays are also an important part of diagnosis. Some changes are seen typically with cruciate disease, which help confirm diagnosis. Cruciate disease predisposes to arthritis development which can be assessed on x-ray. Many dogs who have cruciate disease also have some degree of hip disease (hip dysplasia). This does not necessarily alter the treatment plan but can affect prognosis, so it is important to know about at the time of diagnosis.
Conservative (non-surgical) management is generally not considered appropriate for cruciate ligament rupture. Untreated, the body will form thick scar tissue around the stifle joint to try and counteract instability. In small dogs, this sometimes is enough to allow them to use the leg, however, the joint will develop significant arthritis, and will never regain full function. Rarely, this is our only option if other diseases prevent us from doing surgery.
Surgery is widely considered the most appropriate treatment option and, within reason, the sooner it is performed the better the outcome is likely to be. There are several options available, and your vet will guide you to what is best suited for your pet. Surgery can be divided into two broad categories:
These techniques use prosthetic ligaments to mimic the function of the cruciate ligament and stabilise the joint. The most common is a lateral suture (involving a suture being placed around the outside, or lateral, aspect of the joint) however other techniques are available.
Extra-capsular techniques are generally simpler to perform, less expensive, with fewer risks. They are not as strong however, so are usually recommended for smaller patients, or those who do not lead a very active lifestyle.
Tibial plateau levelling procedures
These techniques aim to correct the instability by changing the biomechanics of the joint. There are several different procedures available which all work to achieve roughly the same thing. They all involve cutting bone and inserting metal implants to hold the pieces in a different position. Examples of tibial plateau levelling procedures are TPLO, TTA and TTO.
These procedures are more invasive than extra-capsular repairs and are significantly more complicated for the surgeon. For this reason, your vet may suggest that your pet goes to see a specialist orthopaedic surgeon to have one of these procedures performed. They are generally considered to give a more robust repair with better long-term outcomes, so are often recommended for very large, young or active patients.
There are few studies that objectively assess outcomes of cruciate surgery; however, one study has demonstrated that dogs who had a TPLO procedure were measured to be weight-bearing more at fixed points post-operatively when compared to patients who had a lateral suture.
In general, the prognosis after cruciate ligament surgery is good. Most procedures aim to achieve a return to the level of exercise considered normal prior to injury. The prognosis is worse for dogs who do not undergo surgical treatment, or those who have concurrent orthopaedic disease such as hip dysplasia. Many dogs will have some arthritis develop because of the injury and subsequent surgery; however, this does not necessarily affect function.
The typical time for a complete recovery from cruciate surgery is 12-16 weeks, though this will vary for individuals. Some dogs recover very quickly while others take time and suffer more muscle loss or are unwilling to trust the leg. This varies greatly with the age and size of the dog, how acute the injury was, and how quickly surgery was performed. Some animals will benefit from physiotherapy or hydrotherapy in the recovery period; your vet will discuss this with you.
Approximately 50% of dogs will go on to require the same surgery in the other hind limb. Cruciate disease in dogs is a degenerative process thought to be due in part to genetics, so often affected dogs will suffer cruciate ligament rupture in both hind-limbs. This can be almost concurrent or be several years apart. Many dogs have surgery of both hind-limbs during their lifetime, and anecdotally often recover from the second surgery faster than the first.
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Page last reviewed: 16th January 2024
Next review due: 16th January 2026