Dog Cruciate Ligament Injury: Consequences of Not Fixing It, Long-Term Effects, and Why Treatment is Crucial

What happens if you don't fix a dog's cruciate ligament?

If a dog's cranial cruciate ligament (CCL) injury is left untreated, it inevitably leads to chronic pain, severe and progressive osteoarthritis, muscle atrophy, and significantly reduced mobility, often impacting the opposite limb as well.

Understanding the Canine Cruciate Ligament

The canine stifle (knee) joint is a complex structure, and central to its stability are the cruciate ligaments – the cranial (anterior) and caudal (posterior) cruciate ligaments. Functionally analogous to the anterior cruciate ligament (ACL) in humans, the cranial cruciate ligament (CCL) in dogs is paramount. Its primary roles are to prevent the tibia (shin bone) from sliding forward relative to the femur (thigh bone) (known as "cranial tibial thrust"), to limit internal rotation of the tibia, and to prevent hyperextension of the joint.

The Nature of a Cruciate Ligament Injury in Dogs

Unlike acute, traumatic ACL tears often seen in human athletes, CCL injuries in dogs are frequently degenerative. This means the ligament weakens over time, often due to chronic stress, conformation, or genetic predispositions, eventually leading to a partial tear that progresses to a full rupture. While a sudden misstep or jump can be the final event, the underlying pathology has typically been developing for months or even years.

Immediate Consequences of an Untreated CCL Rupture

When the CCL ruptures, the stifle joint loses its primary stabilizer, leading to several immediate and debilitating effects:

• Acute Pain: The initial injury causes significant pain, leading to severe lameness. The dog will often hold the leg up or refuse to bear weight on it.
• Joint Instability: Without the CCL, the tibia can slide excessively forward relative to the femur, creating abnormal motion within the joint. This instability is often palpable by a veterinarian as a "cranial drawer sign."
• Secondary Meniscal Damage: The menisci are C-shaped cartilage pads within the joint that act as shock absorbers and help distribute forces. The abnormal motion caused by an unstable joint places immense stress on the menisci, particularly the medial meniscus. A meniscal tear, often a "bucket handle" tear, is a common and painful secondary injury that occurs in a high percentage of untreated CCL ruptures. This significantly worsens pain and lameness.
• Inflammation: The instability and abnormal forces within the joint trigger an inflammatory response, leading to joint swelling (effusion) and further discomfort.
• Muscle Atrophy: Due to pain and disuse, the muscles of the affected limb, particularly the quadriceps and hamstrings, will rapidly begin to atrophy (waste away). This further compromises joint stability and strength.

Long-Term Complications of Neglecting a CCL Injury

The immediate consequences quickly pave the way for a cascade of irreversible long-term problems:

• Progressive Osteoarthritis (OA): This is the most significant and inevitable long-term consequence. The chronic instability, inflammation, and abnormal joint mechanics lead to irreversible damage to the articular cartilage, the smooth protective lining of the bones. The body attempts to stabilize the joint by laying down new bone, leading to the formation of osteophytes (bone spurs). This process results in a stiff, painful, and progressively degenerating joint.
• Chronic Pain: As osteoarthritis progresses, the dog will experience persistent, chronic pain. This pain can fluctuate in intensity but will generally worsen over time, severely impacting the dog's quality of life.
• Reduced Mobility and Function: The combination of pain, stiffness, muscle atrophy, and joint deformity will severely limit the dog's ability to perform normal activities. This includes difficulty walking, running, jumping, climbing stairs, and even lying down comfortably. Their range of motion in the stifle will become significantly restricted.
• Contralateral CCL Rupture: A critical long-term risk is the increased likelihood of rupturing the CCL in the opposite (contralateral) limb. Due to the chronic lameness and compensation, the healthy limb carries a disproportionately higher load, predisposing it to failure. It is estimated that 30-50% of dogs with one CCL rupture will eventually rupture the other.
• Permanent Lameness: Even if the dog learns to cope with the instability, the limb will never regain its full function, and a noticeable lameness will persist, often worsening with activity or changes in weather.

Why Non-Surgical Management is Often Insufficient

While non-surgical (conservative) management strategies (e.g., rest, pain medication, anti-inflammatory drugs, controlled exercise, bracing) may be considered for very small dogs, dogs with partial tears, or those with significant co-morbidities that preclude surgery, they are generally insufficient for achieving long-term stability and comfort in most dogs, especially medium to large breeds.

• Conservative management primarily focuses on pain control and slowing the progression of osteoarthritis, rather than addressing the fundamental instability.
• The joint remains unstable, continuing the cycle of inflammation and degeneration.
• Significant osteoarthritis will still develop, leading to chronic pain and reduced function, albeit potentially at a slower rate in some cases.

The Importance of Veterinary Consultation

Given the severe and progressive nature of untreated CCL injuries, prompt veterinary evaluation is crucial. A veterinarian can accurately diagnose the injury through physical examination and often confirm it with radiographs. They will then discuss the most appropriate course of action, which for most dogs involves surgical stabilization of the stifle joint. Common surgical techniques include Tibial Plateau Leveling Osteotomy (TPLO), Tibial Tuberosity Advancement (TTA), and various extracapsular repair methods. These procedures aim to restore joint stability, reduce pain, and slow the progression of osteoarthritis, significantly improving the dog's long-term prognosis and quality of life.