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DIAGNOSING A CCL TEAR
Cranial Cruciate Ligament (CCL) tears are by far the most common serious orthopedic problem that we encounter in our veterinary practice.  Unfortunately they are often overlooked and therefore misdiagnosed or there is a delay in diagnosis.
 Misdiagnosis or a delayed diagnosis occurs for a couple of reasons.  I believe the most likely reason is based on the behaviour of our pets.  Dogs and cats are very stoic and therefore may not exhibit any obvious signs of pain until a problem is very advanced.  Pets are also unable to tell either their owner or their veterinarian where they are painful.  Many dogs with torn CCLs may also have signs that can easily be misinterpreted as hip dysplasia or arthritis.  Radiographs of the hips may confirm abnormal hips further misleading the veterinarian into thinking that hips are the source of the problem.  This misdiagnosis can typically be avoided by taking a thorough history, thoroughly feeling and manipulating the patients stifles and radiographing the stifles whenever hip radiographs are taken.

While the vast majority of CCL ears occur in mature dogs (greater than 18 months of age), they can occur in immature dogs as well.   While these early tears can occasionally occur in any breed, certain breeds including Laborador Retrievers, Rottweilers, Mastiffs, St. Bernards and Newfoundlanders are particularly prone to tearing CCLs while they are still puppies.

Each patient with a CCL tear is unique and will present differently.  Findings may include one or more of the following:

• A recurring hind limb lameness (may go on for months to years – progressively worsens with time) that seems to improve with restricted activity and/or medications only to recur with increased activity and time.

• A sudden onset of severe lameness where the hind foot is completely held off the ground for a variable period of time.  If the foot is acutely held up it will typically be placed on the ground within 1 to 3 days however a persistent or recurring lameness will continue.

• A dog that just seems lazy and reluctant to climb stairs, play or run since it has torn both CCL’s and therefore doesn’t have “a good leg to stand on”.  These dogs are extremely painful and exhibit a very abnormal gait, however, since both legs are affected it may be difficult to assess lameness since both hind legs look quite similar.

Sitting Posture / Position:

Affected dogs will often appear slow getting up from a sitting position and slow or awkwardly quick (flopping down) when sitting down.  This is due to the discomfort associated with bending the stifle and hock.  They will typically also develop a “lazy sit” where the affected leg is kept out to the side when sitting.  This prevents the stifle (knee) and hock (ankle) from being flexed (bent) since the bending of these joints results in pain.  Note that some normal dogs demonstrate  a “lazy sit” so a change in sitting posture from straight to lazy is what is important in this situation.

Standing Position / Weight Bearing:
If only one CCL is torn the pet will redistribute their weight onto the normal leg.  This will result in the normal paw being pushed flat to the floor with the toes spread a little apart.  Since the dog is not weight bearing well on the affected leg, the paw will not be flat on the floor, the hock may appear straighter and the toes will not be as spread out as in the normal leg.  Another way to determine if a patient is weight shifting is to lift up both back paws independently.   If a dog is very painful on its leg it will not mind having that paw gently lifted off the ground since it will be uncomfortable redistributing its weight onto its good leg.  When the good leg is gently lifted, resulting in weight shifting to the painful leg, the dog may then resist or may even collapse on the affected leg since its unable to adequately bear weight.  If both CCLs are torn these findings typically do not apply since both legs are painful and weight may be evenly distributed over the two equally painful hind legs.  These dogs may have a strange standing position as they redistribute their weight onto their two front legs.  This may look as though the dog is teetering on its front legs and these dogs may have heavily muscled shoulders and front legs due to carrying the majority of the dogs’ weight forward.

Palpating / Manipulation of the Legs (feeling the leg):
It is important to evaluate the entire body since the CCL tear may not be the only issue.  It is also extremely important to evaluate both legs thoroughly, as approximately 20% of the dos we see for evaluation actually have CCL tears in both stifles and owners need to know this prior to proceeding.  Feel for instability in each stifle.  A positive drawer or positive Tibial Compression Test may be present.  These tests are great or terrible depending on the way the results are interpreted.  Positive tests confirm CCL injury, however, NEGATIVE RESULTS DO NOT RULE OUT CCL DISEASE.  To be confident on your test result the patient may need to be sedated or anesthetized so that they are relaxed.  If the CCL tear is partial or very old (stifle scarred down) these tests may be negative however surgery may still be necessary and extremely beneficial.  You may feel joint effusion (swelling), you may find a medial buttress (firm swelling on the inside of the stifle) that is diagnostic of a chronic (old) CCL tear.  Lameness may not initially be evident however after stability tests are performed or after the stifle is fully extended lameness may not be noted.  Pain may be elicited on manipulation of the stifle.

Additional Tests:
Radiographs (x-rays) are the most frequently utilized imaging test.   Since the CCL is “soft tissue” it does not show up on radiographs, however, they may demonstrate swelling within the stifle joint (joint effusion, also known as “water on the knee”) and arthritis (the number one cause of arthritis in the dogs knee is secondary to a CCL).  These findings are strongly supportive of a diagnosis of CCL disease.  The radiographs may also, albeit far less frequently, demonstrate mal-alignment of the bones in the stifle confirming a CCL tear.

Summary:
CCL repair surgeries are our desired first treatment of choice since they can provide far better pain relief and minimize the development of future arthritis.  Medical management in pets is typically reserved for those patients that 1) the owners cannot afford surgery (pain management medications in many cases can actually cost far more in the long run than surgery since these medications are typically required for the remainder of the pets’ life)  2) the owners have refused the surgery performed due to concerns over anesthesia (risk is very low if a pet is healthy and all precautions are taken – even in older pets) or the surgical procedure itself (again, a very low complication rate), or 3) pets who have other serious health conditions where anesthesia and surgery may carry far greater risks.