Swollen joints: foals

Question 1

DDX (6)

Answer 1

• Osteochondritis dissecans
• Osseous cyst-like lesion
• Physitis
• Septic polyarthritis & osteomyelitis
• Salter-Harris fracture
• Patella luxation

Question 2

OCD

• what (2)
• pathology (4)
• aetiology (5)

Answer 2

• articular manifestation of OC
• localised failure of endochondral ossification

Pathology:

• increased articulate cartilage thickness and corresponding defect in subchondral bone
• necrosis of deep chondrocytes
• fibrosis and flap formation
• flap may ossify

Aetiology:

• Rapid growth rate - genetic & high DE
• Mineral imbalance – high P, low Cu (high Zn)
• Biomechanical trauma
• Hormonal factors – eg thyroid hormone
• Genetic factors

Question 3

OCD

• epidemiology (2)
• point of no return (4)

Answer 3

• occurs in growing animals, but CS not seen until older (onset of work)
• Femoropatellar, tarsocrural & fetlock joints most commonly affected

Point of no return
• DIRT: 5mo
• LTR talus: 5mo
• LTR distal femur: 8mo
• Distal MC/MT3 lesions have been reported to repair

Question 4

Hock OCD

• CS (3)
• Sites (3)
• Tx (3)
• prognosis

Answer 4

• Young horses; Warmbloods & Standardbreds
• Tarsocrural joint effusion (“bog spavin”)
• variable lameness; often bilateral
• Distal intermediate ridge of tibia most common site
• Lateral trochlear ridge of talus
• Medial trochlear ridge of talus & medial malleolus of tibia

Tx:
• None
• Conservative (up to 5mo)
• Arthroscopic debridement

• ~75% horses return to their intended use

Question 5

Stifle OCD

• CS (5)
• Radiography (5)
• Tx (3)

Answer 5

CS:
• usually trochlear ridge
• Usually < 2-y-o; Thoroughbreds
• Femoropatellar joint effusion
• Lameness
• Often bilateral

Radiography:
• Medial trochlear ridge, trochlear groove & patella may also be affected
• Radiograph both stifles
• Signs
– Flattening of contour/radiolucency of subchondral bone
– Separate mineralised fragments at affected sites/joint mice
– None

Tx:
• Conservative
• Arthroscopic debridement most common Tx
• Possible to reattach some flaps
–	Surface normal
–	Not loose

Question 6

Osseous cyst-like lesions

• locations (5)
• defintiion
• pathogenesis (3)
• Tx (4)

Answer 6

• Femorotibial joint
–	Medial condyle
–	Lateral condyle
–	Proximal tibia
• Fetlock joint
• PIPJ
• DIPJ
• Antebrachiocarpal joint
• Elbow joint
• Shoulder joint

• cavity containing fibrous tissue ± fluid
• Crack in articular cartilage & subchondral bone
• Inflammation – in response to trauma?
• Focal failure of endochondral ossification (i.e. related to OC)

Tx:
• None
• Conservative
– Box rest
– Controlled exercise programme
– NSAIDs
– Local corticosteroids – best into cyst lining
• Surgical debridement
– Arthroscopic
– Transcortical
• Encourage healing
– Bone graft, bone substitute
– Stem cells, PRP, bone marrow aspirate
– Prognosis: 50 - 75% (age related?)

Question 7

Physitis

• what
• CS (2)
• Tx (2)

Answer 7

• Type V growth plate injury

CS:
• Firm, warm, painful enlargement of medial physis of distal radius or distal MC3/MT3 ± proximal P1
• May cause lameness

Tx:
• Box rest
• Reduce DE; NSAIDs if lame; assess conformation

Question 8

Septic polyarthritis & osteomyelitis

• causes (5)
• pathogenesis in foals vs adults (3)
• where (3)

Answer 8

• Coliforms, Strep, Staph, Rhodococcus equi & Actinobacillus

• Distant septic focus: Infected umbilicus; enteritis; pneumonia
• Haematogenous spread following ingestion immediately following birth or from distant septic focus
• Adults: penetrating wound/ iatrogenic

• Synovial cavities
– Joints: TCJ, fetlock, carpus & stifle most commonly
– Tendon sheath, bursa too

• Bone
– Metaphysis or epiphysis

Question 9

Septic polyarthritis & osteomyelitis

• Dx (7)
• Tx(5)

Answer 9

Dx:
• Progressive lameness (to 5/5)
• May be systemic signs – contrast to adult
• Hot, painful, distended joint(s)
• Generalised swelling extending proximally and distally
• Synovial fluid analysis
• Blood culture
• Radiography
– Focal bone lysis in metaphysis or epiphysis
– Repeat q 7d if –ve

Tx:

• as for adult
• flush synovial cavity
• debridement
• treat primary infection
• monitor