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Joints Developmental - Pathology (view source)

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===Hip dysplasia===
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*Mainly large and giant dog breeds, especially with stocky conformations
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*Seen in cattle - Herefords
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*Subluxation of hip joint due to maldevelopment
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*Not present at bith
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*Inherited + environmental factor involvement (nutrition, exercise)
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*Pelvic muscles are behind the bone development in rapidly growing dogs -> lack of restraint of the joint -> excess movement before acetabulum is fully mature
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*Usually develops within first 6 months of life
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*Varying degrees of severity
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*Pathogenesis:
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**Joint laxity / acetabular dysplasia
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**-> Flattened femoral head +/- mild or severe periarticular [[Musculoskeletal terminology|osteophyte]] formation
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**-> Thickening of femoral head + degeneration of [[Joints - normal#Articular cartilage|articular cartilage]]
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**[[Musculoskeletal terminology|Eburnation]]
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*Predisposes to [[Joints - degenerative#Degenerative joint disease (DJD)|DJD]]
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*Round ligament of femoral head may rupture -> luxation
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===Elbow dysplasia===
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* = '''Ununited anconeal process'''
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*In dogs, especially German Shepherd Dogs, St. Bernards, Labradors
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*Occurs during first few years of life
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*Failure of anconeal centre of ossification to unite with the ulna
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**Normally, they unite between 4-6 months of life
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*May partially or totally separate from each other
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*Intra-articular irritation -> [[Joints - degenerative#Degenerative joint disease (DJD)|DJD]] with [[Musculoskeletal terminology|osteophyte]] formation within the joint
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===Osteochondrosis===
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[[Image:Pig elbow osteochondrosis.jpg|right|thumb|100px|<small><center>Osteochondrosis in pig elbow (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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[[Image:Osteochondrosis dissecans.jpg|right|thumb|100px|<small><center>Osteochondrosis dissecans (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
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*Defect in cartilage growth (i.e. '''dyschondroplasia''')
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*In growing animals: large breeds of dogs (4-8 months), pigs (5-7 months) and horses (weeks - 2 years)
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*Involves both the [[Bones - normal#Physis (Growth plate)|growth plate]] and the immature [[Joints - normal#Articular cartilage|joint cartilage]]
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*Multifactorial:
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**Trauma
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**Genetic
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**Rapid growth
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**Ischaemia
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**Nutritional
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*Essentially idiopathic
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*Failure of [[Bones - normal#Bone development|endochondral ossification]]
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*Lesions bilateral in 70% of cases but lameness often unilateral, sometimes no clinical signs
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*Some authors consider this condition more generalised, in which case e.g. [[Joints - developmental#Elbow dysplasia|ununited anconeal process]] would be part of osteochondrosis syndrome
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Different manifestations include:
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*'''1. ''Osteochondrosis dissecans''''' (OCD):
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**Retained cartilage cores
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***White, wedge-shaped areas of retained cartilage in the metaphysis
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***Clefts -> separation of cartilage from bone -> flaps or free '''joint mice'''
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***May interfere with joint function
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**Lysis → bone cysts
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**Focal disruption of [[Bones - normal#Bone development|endochondral ossification]]
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**-> Angular limb deformities and [[Joints - degenerative#Degenerative joint disease (DJD)|degenerative joint disease]]
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**May be present together with '''synovitis'''
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**Predilection sites:
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***<u>In dogs:</u>
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****Proximal humerus
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****Lateral femoral condyle
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****Coronoid process of ulna
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***<u>In pigs:</u>
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****Humeral and medial femoral condyles
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****Anconeal process of elbow
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***<u>In horses:</u>
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***Medial femoral condyle
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***Distal tibia
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**''Osteochondrosis dissecans'' in dogs:
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***Grossly:
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****Lesion in central part of the caudal aspect of developing ossification centre in humeral head
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***Histologcally:
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****Lesion filled with [[General Pathology - Chronic Inflammation#Granulation tissue|granulation tissue]] (fibroplasia)
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****Surrounding thickened bone spicules
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****Cap of thickened [[Joints - normal#Articular cartilage|articular cartilage]] over the defect
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****-> May fragment - joint mice
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****Calcified cartilage fragments may be in the posterior pocket of joint capsule
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*****May grow through synovial fluid nourishment
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*'''2. Epiphysiolysis'''
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**Not associated with retention of cartilage
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**Separation of epiphysis from the metaphysis
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**Likely to be due to trauma to degenerated [[Bones - normal#Physis (Growth plate)|growth plate]]
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**Possibly the basis of ununited anconeal process and ununited coronoid process in dogs
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===Arthrogryposis===
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*Persistent congenital flexure of a joint in conjunction with muscle contraction
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*Caused by:
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**Inactivity or paralysis in utero
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**Spinal dysraphism
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**Intrauterine viral infections
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**Toxic plants (poison hemlock, lupine)
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**Cause persitent contraction of uterus -> fetal compression
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*Arthrogryposis and [[Oral Cavity - Cavity & Gingiva#Cleft Palate|palatoschisis]] in Charolais cattle
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===[[Bones Developmental - Pathology#Angular limb deformity|Angular limb deformity]]===
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