developmental MSK diseases

Question 1

What is osteochondrosis

Answer 1

a developmental skeletal disorder that occurs in a range of domestic animals (mostly horses, dogs and pigs)
- characterized by focal failures of the endochondral ossification process that occur is well defined species specific prediliction sites in young animals
- lesions are often bilateral (always check both limbs)

the failure of endochondral ossification

Question 2

what is the pathogenesis of osteochondrosis

Answer 2

• failure of vessels in cartilage canals leading to chondronecrosis
• biomechanical forces (primary: shearing of cartilage to bone interface, secondary:shearing following cartilage canal failure and chondronecrosis)
• molecular alterations in endochondral ossification
• genetic factors

Question 3

what is osteochondritis

Answer 3

extensions of lesions to the articular surface causing inflammation of the joint

Question 4

what is osteochondritis dissecans

Answer 4

presence of a dissecting osteochondral flap or loose fragment of the joint

Question 5

what happens if you pass the “age of no return” in the treatment of an animal with osteochondrosis

Answer 5

if the legion is evident radiographically and has not been treated beyond this age it is permanent and cannot be fixed

Question 6

what are the maifestations of osteochondrosis

Answer 6

• thickened cartilage
• intra-articular cartilage fragments (OCD) (may ossify after seperation)
• subchondral bone cysts

Question 7

what are the clinical signs of osteochondrosis

Answer 7

• joint effusion (big bump on joint)
• +/- lameness. lameness more likely if the subchondral bone is involved or if there is synovitis, but cartilage itself is aneural so may not see any lameness
• onset of clinical signs often associated with exercise or trauma (original lesion happens in growth but may not present until mature)
• subchondral bone cyst (lameness as involved with bone, less likely if deep within bone, +/- joint effusion)

Question 8

what are the osteochondrosis predilection sites in the horse

Answer 8

• tibiotarsal joint
• femoropatellar joint
• fetlock joints

less common includes shoulder, elbow and hip

Question 9

what are the common predilection sites in dogs for osteochondrosis

Answer 9

• shoulder
• stifle
• elbow

Question 10

What is physeal dysplasia or “Physitis”

Answer 10

• an accquired condition characterised by gross enlargement of the physis +/- metaphysis
• probably due to mismatch between metaphyseal bone strength and applied loads
• in rare cases may lead to early closure and subsequent ALD

Question 11

what is angular limb deformity

Answer 11

deviation in the long axis of limb in frontal plane
- can be congenital or aqcuired
- valgus: limb deviates laterally distal to the site of deformity
- varus: limb deviates medially distal to the site if deformity

Question 12

what is congential angular limb deformity

Answer 12

• pathogenisis includes incomplete ossification of cuboidal carpal bones in premature/dysmature foals
• may also occur secondary to lax periarticular ligaments or epiphyseal dysplasia