Cranial Cruciate Ligament Rupture
What is a Cranial Cruciate Ligament Rupture (CCLR)?
A pet’s stifle joint corresponds to the human knee, and the cranial cruciate ligament is comparable to the anterior cruciate (ACL) ligament in humans. Just as in humans, a partial or complete rupture of this ligament is debilitating and can be extremely painful. Cranial cruciate ligament rupture (CCLR) is one of the most common orthopaedic problems in dogs, and is occasionally seen in cats too. In CCLRs, the ligament may either be partially or completely torn. Partial ruptures will eventually progress onto a complete rupture if left untreated. If left untreated, CCLR results in additional degenerative changes in the joint and eventually, this may lead to osteoarthritis.
Causes of CCLR & Risk Factors
There are certain risk factors that could increase the likelihood of a pet having a CCLR. These include, but are not limited to:
- Obesity
- Existing knee instability (e.g. medial patellar luxation or previous partial tear)
- Existing knee osteoarthritis
- Abnormal forces passing through the knee joint due to developmental disorders (e.g. hip dysplasia)
- Lack of proper conditioning for the activity taking place (e.g. a normally sedentary dog that suddenly engages in vigorous play)
CCLRs can be of acute (sudden) or chronic (happens over time) in nature. Acute CCLR is typically seen when dogs are engaged in some form of physical activity, during which the joint is extended beyond its normal limits or rotates to an extreme degree such that the ligament tears (similar to those seen in our All Blacks rugby players). Chronic CCLRs typically occurs when the ligament has weakened in strength over time; this may be due to a number of factors such as age-related changes, obesity or poor posture.
What are the Clinical Signs of CCLR?
The first sign of CCLR is typically hindlimb lameness. The degree of lameness depends on whether the rupture is partial or complete; acute or chronic in nature; and the dog’s level of pain tolerance. As a result, some dogs may be slightly lame while others are completely unable to place any weight on the affected limb. Other potential signs that may indicate a pet has a CCLR may include:-
- Pain, stiffness and/or swelling at the knee joint
- Wasting (atrophy) of the thigh muscles in the affected limb
- Sitting abnormally in a position e.g. one hindlimb is tucked under the body and the other limb is sticking out away from the body (that is usually the affected limb)
- Difficulty in getting up
- Decreased activity level / reluctance to exercise or go for walks
Diagnosis
The diagnosis of CCLR is usually made based on clinical signs and physical examination findings. Your veterinarian will evaluate the affected knee joint for abnormal movement/instability, if other structures within the knee are also injured (e.g. the meniscus) as well as if any pain, swelling, or muscle wastage is observed. The meniscus is a C-shaped fibrous structure located within the knee joint, and acts as a “shock-absorber” during weight-bearing and movement. Up to 35-75% of CCLRs have concurrent injury to the meniscus1. Meniscal injury is challenging to diagnose, and it is estimated that only 10-20% of them are able to be identified at the time of consult. In general, meniscal injury is best diagnosed at time of surgery1.
Treatment
Your veterinarian may recommend medical or surgical treatment for CCLR. Treatment recommendations are based on several factors, including the severity of the lameness, whether it is a complete or partial rupture, the condition of the other structures within the knee joint (such as the meniscus), the size and overall health of the patient.
Medical (conservative) management typically consists of strict rest for 3-4 weeks and appropriate pain relief medication. Once your pet gets over the initial phase of recovery, it is very important that you keep his/her weight under control, and follow a veterinarian-approved exercise plan. In many cases, small dogs (<10-15kg) and cats can do well with appropriate medication alone. Conservative management may also be recommended if your pet is not a good candidate for surgery (e.g. concurrent health issues which may pose a significant risk to your pet being under anaesthesia).
Surgical treatment involves stabilising the affected knee joint in order to achieve more “normal” joint movement. There are several surgical procedures that can accomplish this successfully – some of these procedures may be able to be done at your local veterinarian’s; others may require a referral to a specialist orthopaedic surgeon. If your pet is a suitable candidate for surgery, your veterinarian will discuss the surgical options with you. It is also important to realise that even if no apparent injury to the meniscus is noted at the time of surgery, a further 20% of dogs may develop “late” meniscal injury in the initial 16 week – 9month post-operative period when your pet is recuperating from the CCLR1. After the surgery, your pet will be sent home with a set of discharge instructions regarding limitations to activity as well as other pertinent post-operative care instructions. Be sure to closely follow your veterinarian’s instructions, because even the best and most successful surgery can result in complications if post-operative care at home is inadequate.
IMPORTANT: A significant percentage (at least 40%)1 of dogs that have a CCLR in one hindlimb typically rupture the cranial cruciate ligament in their other hindlimb within 1-2 years. A large proportion of pets with a partial CCLR will likely progress onto having a complete CCLR with medical management.
References
1 Kowaleski MP, Boudrieau RJ and Pozzi A. Chapter 62: Stifle joint. In: Tobias KM & Johnston A (ed).Veterinary Surgery: Small Animal Volume 1 . Pp 906-995, Saunders, Canada, 2012.
The above information is provided for educational purposes only and not intended or implied to be a substitute for professional veterinary medical advice, diagnosis or treatment; and should not be relied on solely as veterinary advice. If you are worried your pet may have patellar luxation, please phone us on (06) 3588675 to book them in for a check over.
Parts of this information sheet have been adapted from the Vetlearn Compendium Care Guides.