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* [[Osteochondrosis - Small Animal]]
[[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>]]
* [[Osteochondrosis - Equine]]
[[Image:Osteochondrosis dissecans.jpg|right|thumb|100px|<small><center>Osteochondrosis dissecans (Image sourced from Bristol Biomed Image Archive with permission)</center></small>]]
*Defect in cartilage growth (i.e. '''dyschondroplasia''')
*In growing animals: large breeds of dogs (4-8 months), pigs (5-7 months) and horses (weeks - 2 years)
*Involves both the [[Bones - Anatomy & Physiology|growth plate]] and the immature [[Joints - Anatomy & Physiology#Articular cartilage|joint cartilage]]
*Multifactorial:
**Trauma
**Genetic
**Rapid growth
**Ischaemia
**Nutritional
*Essentially idiopathic
*Failure of [[Cartilage - Anatomy & Physiology|endochondral ossification]]
*Lesions bilateral in 70% of cases but lameness often unilateral, sometimes no clinical signs
*Some authors consider this condition more generalised, in which case e.g. [[Joints Developmental - Pathology#Elbow dysplasia|ununited anconeal process]] would be part of osteochondrosis syndrome
Different manifestations include:
*'''1. ''Osteochondrosis dissecans''''' (OCD):
**Retained cartilage cores
***White, wedge-shaped areas of retained cartilage in the metaphysis
***Clefts -> separation of cartilage from bone -> flaps or free '''joint mice'''
***May interfere with joint function
**Lysis → bone cysts
**Focal disruption of [[Cartilage - Anatomy & Physiology|endochondral ossification]]
**-> Angular limb deformities and [[Joints Degenerative - Pathology#Degenerative joint disease (DJD)|degenerative joint disease]]
**May be present together with '''synovitis'''
**Predilection sites:
***<u>In dogs:</u>
****Proximal humerus
****Lateral femoral condyle
****Coronoid process of ulna
***<u>In pigs:</u>
****Humeral and medial femoral condyles
****Anconeal process of elbow
***<u>In horses:</u>
***Medial femoral condyle
***Distal tibia
**''Osteochondrosis dissecans'' in dogs:
***Grossly:
****Lesion in central part of the caudal aspect of developing ossification centre in humeral head
***Histologcally:
****Lesion filled with [[Granulation Tissue|granulation tissue]] (fibroplasia)
****Surrounding thickened bone spicules
****Cap of thickened [[Joints - Anatomy & Physiology#Articular cartilage|articular cartilage]] over the defect
****-> May fragment - joint mice
****Calcified cartilage fragments may be in the posterior pocket of joint capsule
*****May grow through synovial fluid nourishment
*'''2. Epiphysiolysis'''
**Not associated with retention of cartilage
**Separation of epiphysis from the metaphysis
**Likely to be due to trauma to degenerated [[Bones - Anatomy & Physiology|growth plate]]
**Possibly the basis of ununited anconeal process and ununited coronoid process in dogs
[[Category:Joints - Developmental Pathology]]