27.6.2: Young horse joint disease

Question 1

JOCC

Answer 1

Juvenile osteochondral conditions (JOCC)
(Used to be called developmental orthopaedic disease)

Question 2

Clinical signs of joint disease in young animals

Answer 2

• Often silent (no clinical signs); more often than not, horses will not be lame.
• Varying degree of joint effusion
• Varying degree of lameness

Question 3

What should you pay particular attention to on the lameness examination of the young animal when you suspect joint disease?

Answer 3

• Pay special attention to reaction to flexion tests -> will likely be painful especially if large effusion in the joint
• Possible lameness from synovitis/ loose fragments in the joint
• Stifle and shoulder often more lameness-associated; however still be systematic, start at the limb and work up

Question 4

Causes of JOCC

Answer 4

Multifactorial
* Focal failure of endochondral ossification (epiphyseal or metaphyseal growth cartilage)
* Polygenetic heritable disease
* Overnutrition/ mineral imbalances/ rapid growth rate - less or not supported by research

Question 5

Osteochondrosis dissecans

Answer 5

presence of a fragment or flap (the potential endpoint of the osteochondrosis process that begins with incomplete endochondral ossification).
* Occurs on the sagittal ridge of MCIII / MTIII
* 3 types
* Type 1: flattening or defect in sagittal ridge
* Type 2: fragmentation within the flattening
* Type 3: free or loose body fragments in joint

Question 6

Answer 6

Osteochondrosis dissecans

Question 7

What radiographic views do you need to evaluate OCD in the fetlock?

Answer 7

• Lateromedial - need to radiograph a flexed view
• More valuable for detection of OCD in the fetlock
• It is not always a huge fragment - subtle radiolucencies on a dorsopalmar / dorsoplantar view

Question 8

What kind of fragmentation in OCD is more problematic?

Answer 8

Fragments are more likely to be a problem if in the joint.

Question 9

What are the 3 types of fragment that occur with osteochondrosis of the fetlock joint?

Answer 9

1. OCD of the sagittal ridge
2. Avulsion fragmentation (back of leh)
3. Dorsal margin fragmentation (front of leg)

Question 10

Aetiology and signalment of subchondral lucencies

Answer 10

• Aetiologies less clear/ age-dependent
• In horses <2 years old - likely osteochondrosis
• In horses >2 years old - trauma-induced lesion most likely

Question 11

How should you diagnose JOCC?

Answer 11

Take 4 orthogonal views on radiography

Question 12

Which radiographic view is shown here? How do you know?

Answer 12

This is a DMPLO view.
It highlights the lateral trochlear ridge so it must be this view.

Question 13

What abnormality is circled here? What disease process is it indicative of?

Answer 13

Huge fragment of the distal tibia
This is indicated of OCD (JOCC)

Question 14

What abnormalities are indicated by the arrow and circle?

Answer 14

Soft tissue effusion and fragment on the dorsal aspect (consistent with OCD/JOCC).
* Will need oblique views to properly locate the fragment

Question 15

What challenges are there relating to the diagnosis of JOCC?

Answer 15

• Experience of owners
• Owner expectations/ purpose of horse
• Lesions often silent until significant increase in exercise
• Horses from different disciplines will start at a different age
• Temperament may not be amenable to all diagnostic steps
• Some lesions may be cartilagenous only so not visible on radiographs

Question 16

True/false: sometimes OCD lesions can disappear early in the horse’s life.

Answer 16

True
* Stifle and hock OCD could appear at 5 months old but disappear by 1 year old
* Do not do anything about OCD before the horse has turned 1 year old!

Question 17

Treatment and management of OCD

Answer 17

2 options
* Leave as it is
* Remove (usually under GA; standing sedation not widespread yet)

Decision depends on intended purpose of horse/ work, ownership of horse, whether sale intended in future, finances, risk, prognosis

Question 18

What is the general rule of thumb for management of the following JOCC lesions?
* Loose fragments in a joint
* Flattening
* Subchondral lucencies

Answer 18

• Loose fragments in a joint -> removal needed
• Flattening -> can monitor and see
• Subchondral lucencies -> more complicated

Question 19

How will you manage this case?

Answer 19

• This fragment must be removed
• It is very big and will scratch and damage the cartilage -> this is a ticket to osteoarthritis

Question 20

What do you think of this cartilage? What is the prognosis?

Answer 20

• Normal cartilage will be totally smooth; this is very abnormal
• Prognosis is negatively affected when cartilage lesions are full thickness as some of these are