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The most common cause of patellar luxation is '''congenital medial patellar luxation in small dogs''' such as miniature Poodles, Chihuahuas and Yorkshire Terriers.
The most common cause of patellar luxation is '''congenital medial patellar luxation in small dogs''' such as miniature Poodles, Chihuahuas and Yorkshire Terriers.
Medial patellar luxation is the most common luxation in all sizes of dogs. '''Lateral luxation''' is much rarer, and in larger dogs carries a poorer prognosis.
Medial patellar luxation is the most common luxation in all sizes of dogs. '''Lateral luxation''' is much rarer, and in larger dogs carries a poorer prognosis. Lateral luxation may also occur in horses.
Signs usually appear before '''2 years of age'''.
Signs usually appear before '''2 years of age'''.
==Clinical Signs==
==Clinical Signs==
'''Acute traumatic patellar luxation''' can be medial or lateral and is associated with acute, non-weightbearing lameness and pain on manipulation of the joint.
'''Acute traumatic patellar luxation''' can be medial or lateral and is associated with acute, non-weightbearing lameness and pain on manipulation of the joint.
'''Congenital medial luxations''' are graded according to clinical signs and palpation findings:
'''Congenital medial luxations''' are graded according to clinical signs and palpation findings:
:'''Grade 1''': Patella luxated medially easily, returns when release, no crepitation or bony deformity and no/infrequent clinical signs
:'''Grade 1''': Patella luxated medially easily, returns when released, no crepitation or bony deformity and no/infrequent clinical signs
:'''Grade 2''': Spontaneous luxation occurs, with a non-painful, skipping lameness. There may be mild bony deformities such as internal rotation of the tibia and abduction of the hock.
:'''Grade 2''': Spontaneous luxation occurs, with a non-painful, skipping lameness. There may be mild bony deformities such as internal rotation of the tibia and abduction of the hock.
:'''Grade 3''': The patella is permanently luxation, but can be manually returned. There is marked tibial rotation and a shallow trochlear groove. Often bilateral, crouched gait.
:'''Grade 3''': The patella is permanently luxated, but can be manually returned. There is marked tibial rotation and a shallow trochlear groove. It is often bilateral and results in crouched gait.
:'''Grade 4''': Permanent, non-reducible luxation of the patella. Tibia rotated 60-90° relative to the sagittal plane. Severe bony deformities develop if not corrected. Crablike posture and abnormal gait.
:'''Grade 4''': Permanent, non-reducible luxation of the patella. Tibia is rotated 60-90° relative to the sagittal plane. Severe bony deformities develop if not corrected. Crablike posture and abnormal gait will be present.
There may be muscle atrophy in the affected limb.
There may be muscle atrophy in the affected limb.
'''History, clinical signs and palpation''' usually allow diagnosis of the condition and permit grading of congenital medial patellar luxation.
'''History, clinical signs and palpation''' usually allow diagnosis of the condition and permit grading of congenital medial patellar luxation.
'''Radiography''': these can document the luxation and are useful to assess bony deformity and degenerative joint changes.
'''Radiography'''can document the luxation and is useful to assess bony deformity and degenerative joint changes.
'''Skyline views''' of the distal femur are usefuly pre and post-operatively to assess the depth and contour of the femoral trochlea.
'''Skyline views''' of the distal femur are useful pre and post-operatively to assess the depth and contour of the femoral trochlea.
==Treatment==
==Treatment==
Treatment should be made individual for each patient, as there are such varying presentations and causes for the condition.
Treatment should be individual for each patient, as there are such varying presentations and causes for the condition.
'''Traumatic luxations''' should be repaired by suturing the medial or lateral fascial defect.
'''Traumatic luxations''' should be repaired by suturing the medial or lateral fascial defect.
This can be achieved by:
This can be achieved by:
*'''Tibial tuberosity transposition'''
*'''Femoral trochleoplasty''' to deepen the groove: abrasion trochleoplasty, recession trochleoplasty
*'''Wedge resection'''
*'''Releasing incisions''' and imbrication of the capsular tissues
*'''Lateral rotation of the tibia'''
'''Post-operatively''': exercise restriction for 4-6 weeks and passive range-of-motion exercises, weight loss and NSAIDs
'''Post-operatively''': exercise restriction for 4-6 weeks and passive range-of-motion exercises, weight loss and [[NSAIDs]] are recommended.
The luxation can recur if there was inadequate correction of the deformity.
==Prognosis==
==Prognosis==
Slatter, D. (2002) '''Textbook of small animal surgery''' ''Elsevier Health Sciences''
Slatter, D. (2002) '''Textbook of small animal surgery''' ''Elsevier Health Sciences''
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[[Category:Musculoskeletal Diseases - Dog]]
[[Category:Musculoskeletal Diseases - Cat]]
[[Category:Musculoskeletal Diseases - Horse]]
[[Category:Expert Review]]
[[Category:Joints - Degenerative Pathology]]
[[Category:Joints - Degenerative Pathology]]