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MCP / MTP joint: disease – overview
Synonym(s): Fetlock joint disease
Introduction
- Incidence: the fetlock is a common site for both congenital and acquired conditions associated with lameness.
- Cause: many causes of lameness including:
- Fractures; chip, intra-articular, sesamoidean.
- Degenerative joint disease Musculoskeletal: osteoarthritis (joint disease) .
- Sesamoiditis Proximal sesamoid: sesamoiditis .
- Synovitis; chronic proliferative MCP / MTP joint: chronic proliferative synovitis , traumatic, idiopathic.
- Ligamentous; sprains of collateral and suspensory ligaments, constriction of annular ligaments.
- Luxations/subluxation MCP / MTP joint: luxation .
- Rupture of associated tendons and ligaments.
- Infection; osteitis Bone: osteitis - septic /osteomyelitis, infectious arthritis.
- Osteochondrosis Bone: osteochondrosis and subchondral bone cysts Bone: subchondral cysts .
- Flexural MCP / MTP joint: flexural deformity and angular limb deformities Musculoskeletal: flexural deformity .
- Subchondral bone disease.
- Palmar osteochondral disease (POD).
- Signs: variable. Some conditions, eg idiopathic synovitis, cause deformity without lameness.
- Diagnosis: clinical examination and range of ancillary aids including joint anesthesia Forelimb: joint anesthesia Hindlimb: joint anesthesia , radiography Forelimb: radiography Hindlimb: radiography and ultrasonography.
- Treatment: depends on cause.
- Prognosis: depends on cause.
Presenting signs
- Forelimb or hindlimb lameness; severity depends on cause.
- Unilateral, bilateral or quadrilateral.
- Pain or resentment on flexion of fetlock joint.
- Fetlock effusion.
- Swelling around fetlock.
- Deviation of limb distal to fetlock.
Age predisposition
- Septic arthritis in foals <4 months age.
- Many angular/flexural deformities present at birth or develop shortly afterwards.
- Osteochondrosis; lesions develop very early in life before 12 months of age but may not manifest clinically until 2-5 years old.
- Degenerative conditions tend to occur in older animals or secondary to another primary fetlock joint condition.
Cost considerations
- Some conditions are career-threatening.
- Costs of diagnostic workup and possible treatment.
- Ongoing treatment for degenerative conditions.
Pathogenesis
Etiology
Trauma- Most common cause of acquired fetlock conditions
. - Fractures may be chip, condylar, intra-articular of the proximal phalanx or MC3, or involve the sesamoids Proximal phalanx: fracture MC / MT 3: fracture - condylar Proximal sesamoid: fracture .
- Sesamoid conditions; sesamoiditis, osteitis of axial border of proximal sesamoid bones Proximal sesamoid: sesamoiditis .
- Luxations associated with rupture of lateral or medial collateral ligament (severe trauma; more common in hindlimb), or with avulsion fractures MCP / MTP joint: luxation .
- Subluxation .
- Capsulitis/synovitis following single or repeated episodes of trauma MCP / MTP joint: chronic proliferative synovitis .
- Proliferative (villonodular) synovitis: may follow chronic trauma MCP / MTP joint: chronic proliferative synovitis .
- Constriction of annular ligament Annular ligament: constriction .
- Degenerative joint disease secondary to many of the above conditions Musculoskeletal: osteoarthritis (joint disease) .
- Traumatic rupture of the suspensory apparatus with or without fracture of the proximal sesamoid (usually forelimb).
- Subchondral bone injuries.
- Desmitis of ligaments associated with the MCP/MTP joints, eg collateral, suspensory Suspensory ligament: desmitis - midbody , DDFT Deep digital flexor tendon: tendinitis .
- Synovial effusion (fetlock 'windpuffs').
- Pressure sores from too tight bandages/boots
.
Infectious
- Septic arthritis may occur secondary to trauma Joint: septic arthritis - adult or via hematogenous spread (rare) Joint: septic arthritis - foal
. - Osteomyelitis of the axial border of the proximal sesamoid bones Bone: osteitis - septic may be associated with septic tenosynovitis, septic arthritis or penetrating injury.
Developmental
- Osteochondrosis MCP / MTP joint: developmental orthopedic diseases , especially of the dorsal sagittal ridge of MC3
MCP / MTP joint: developmental orthopedic diseases : may result in osteochondral fragmentation, especially from the palmar aspect of the proximal phalanx (forelimb) or dorsoproximal aspect of proximal phalanx (hindlimb) Proximal phalanx: fracture . - Physitis/dysplasia
.
Congenital and perinatal conditions
- Angular limb deformities Musculoskeletal: angular deformity : valgus and varus.
- Flexural deformity MCP / MTP joint: flexural deformity .
Immune-mediated
- Immune-mediated polysynovitis uncommon, but may involve the carpal joint Joint: immune-mediated polysynovitis .
- Lyme disease Borreliosis .
Miscellaneous
- Tumors are extremely rare.
- Osseous cyst-like lesions occur in the distal weightbearing surface of the condyles, especially medial, of MC3, and the proximal phalanx Bone: osseous cyst-like lesions .
Predisposing factors
General- Depends on individual condition.
- Many of the traumatic conditions are predisposed by poor fetlock conformation, eg angular limb deformities or excessive sloping pasterns. In addition, poor foot conformation, including long toe/low heel syndrome and mediolateral imbalances can increase the incidence of fetlock disease.
- The fetlock joint is a high motion joint and is injured mainly in fast work such as galloping or other athletic activities.
Pathophysiology
- The fetlock joint comprises the articulations between the distal third metacarpal/metatarsal bone (MC3/MT3), the proximal phalanx and both proximal sesamoid bones.
- The MTP joint is usually more upright than the MCP joint and has a greater normal range of flexion.
- They are high motion joints which are heavily loaded and exposed to complex torsion forces during exercise/work.
- There is a complex ligamentous arrangement around the fetlock joint which constrains its normal movement almost exclusively to sagittal motion.
- The suspensory apparatus attaches to the proximal sesamoid bones proximally at the suspensory branches and distally at the distal sesamoidean ligaments.
- See also: Joint: synovial pathobiology Joint: synovial pathobiology .
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
Other sources of information
- Richardson D W (2003) Metacarpophalangeal Joint. In: Diagnosis & Management of Lameness in the Horse. Eds: Ross M W & Dyson S J. Saunders, USA. pp 348-362.
- Ross M W (2003) Metatarsophalangeal Joint. In: Diagnosis & Management of Lameness in the Horse. Eds: Ross M W & Dyson S J. Saunders, USA. pp 420-433.
- Bertone A L (2002) The Fetlock. In: Adams Lameness in Horses. 5th edn. Lippincott, Williams & Wilkins, USA. pp 768-799.