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Cranial Cruciate Ligament Injury 219

Staffordshire terriers, but all dog sizes are stifle usually limited by an intact cranial Initial Database
cruciate ligament.
affected. • In dogs, CrCL rupture is usually due to • Palpation of stifle joints for instability (may
VetBooks.ir in Newfoundlands, Labrador retrievers, and degeneration rather than direct trauma. ○ Cranial drawer sign: manual cranial Diseases and Disorders
require sedation)
• Genetic predisposition has been demonstrated
displacement of tibia relative to femur
The cause of this degeneration is unknown:
boxers.
RISK FACTORS conformation problems, collagen abnormali-
ties, abnormalities in ligament homeostasis,
• Hyperadrenocorticism, autoimmune disease, and immune disease may play a role.
cutaneous asthenia • In cats and in both species with multiple
• Obesity ligamentous injury, direct trauma is usually
• Ovary removal the cause.
ASSOCIATED DISORDERS DIAGNOSIS
• Meniscal injury (usually medial) very com-
monly accompanies CrCL rupture. Diagnostic Overview
• Patellar luxation Presence of the characteristic hindlimb lameness
• Osteoarthritis combined with evidence of stifle effusion on
• Immune-mediated arthritis physical examination and radiographs suggests
CrCL disease. Absence of pain on manipulation,
Clinical Presentation of cranial drawer sign, or of cranial tibial thrust
DISEASE FORMS/SUBTYPES does not rule out cranial cruciate rupture as the
• Traumatic CrCL tears source of the lameness.
• Degenerative CrCL tears
• Avulsion of the insertion of the CrCL: Differential Diagnosis
immature dogs • Patellar luxation
• Isolated caudal cruciate ligament tears • Lumbosacral disease
(rare) • Hip dysplasia or osteoarthritis
• Multiple ligamentous injury • Iliopsoas strain
• Bone/joint neoplasia
HISTORY, CHIEF COMPLAINT • Osteochondrosis of the lateral femoral condyle
• Variable lameness of one or both hindlimbs; • Inflammatory arthritis
onset acute or progressive • Caudal cruciate or collateral ligament injury
• Lameness may worsen with exercise and (uncommon)
improve with rest. • Long digital extensor tendon avulsion CRANIAL CRUCIATE LIGAMENT INJURY Palpa-
(uncommon) tion of the stifle joint for cranial drawer motion of
PHYSICAL EXAM FINDINGS • Isolated meniscal injury (boxers almost the tibia relative to the femur with cranial cruciate
• Unilateral or bilateral hindlimb lameness: exclusively) ligament insufficiency.
affected limb may be held up in acute injuries
but will be weight bearing with more chronic
affliction, although affected limb is still
off-weighted when the animal is standing
(see Video).
• Affected stifles are externally rotated and
more flexed than normal when walking.
• Stifle joint effusion and thickening of joint
capsule is often most pronounced over medial
aspect of proximal tibia (medial buttress
formation).
• Asymmetrical sitting position with one stifle
abducted
• Cranial drawer sign and cranial tibial thrust
(see Initial Database below) may or may not
be elicited.
• Meniscal clicking may be present during
joint manipulation.
• With caudal cruciate rupture, the tibia can
be caudally displaced relative to the femur
(caudal drawer sign).
• With multiple ligamentous injury, the
cranial and caudal drawer sign as well as
mediolateral instability can be elicited; stifle
may be obviously luxated.
Etiology and Pathophysiology
• Biomechanical instability of the stifle joint
results from an imbalance of forces necessary CRANIAL CRUCIATE LIGAMENT INJURY Palpation of the stifle joint using tibial compression test for cranial
to control the cranial tibial thrust, excessive cruciate ligament injury. With cranial cruciate ligament injury, flexion of the hock causes cranial displacement
internal rotation, and hyperextension of the of the tibia.

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