Collateral desmitis of the distal interphalangeal joint in 18 horses (2001-2002).
Authors: Dyson S J, Murray R, Schramme M, Branch M
Journal: Equine veterinary journal
Summary
# Collateral Desmitis of the Distal Interphalangeal Joint: Diagnostic Challenges and Clinical Patterns Collateral ligament injuries at the distal interphalangeal joint represent an underrecognised cause of foot lameness, yet they frequently escape detection using conventional ultrasonography and radiography. Between 2001 and 2003, Dyson and colleagues identified 18 horses with confirmed collateral desmitis through imaging, of which 44% (8 horses) showed no ultrasonographic evidence of ligament damage—highlighting a significant diagnostic pitfall for clinicians relying solely on ultrasound. The medial collateral ligament was affected in 72% of cases, predominantly in the forelimbs, and whilst lameness consistently worsened on circles (suggesting DIP joint dysfunction), localising clinical signs were often absent; palmar digital analgesia improved lameness in 87% of horses, though only 6 became completely sound. MRI proved superior for both identifying injuries missed on ultrasound and detecting concurrent soft tissue pathology—notably that 61% of affected horses had additional lesions involving the deep digital flexor tendon, navicular structures or distal sesamoidean impar ligament. For practitioners encountering persistent foot lameness unresolving with conventional therapy, this work underscores the value of advanced imaging (particularly MRI) over repeated ultrasonography, and suggests that collateral DIP joint injuries warrant inclusion in diagnostic protocols, especially when regional analgesia provides only partial improvement.
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Practical Takeaways
- •Collateral ligament desmitis of the DIP joint should be considered in cases of foot lameness, particularly when lameness worsens in circles; ultrasound can miss lesions so MRI is recommended for definitive diagnosis
- •Response to palmar digital analgesia (87% improvement) suggests the collateral ligaments of the DIP joint are major pain sources in foot lameness, so careful assessment of this region is warranted
- •Concurrent soft tissue injuries are common (61% of cases), so imaging should evaluate the entire palmar/plantar foot structures including DDFT, navicular region, and distal sesamoidean ligaments
Key Findings
- •18 horses with DIP joint collateral ligament desmitis were identified: 3 detected by ultrasonography alone, 7 by both ultrasound and MRI, and 8 only by MRI, indicating ultrasound produces false-negative results
- •Medial collateral ligament was injured in 13 of 18 horses (72%), with 17 forelimb and 1 hindlimb injury
- •Lameness improved with palmar digital analgesia in 16 horses (87%) but only improved with intra-articular DIP joint analgesia in 6 of 15 horses (40%)
- •11 of 18 horses (61%) had concurrent soft tissue injuries including DDFT, distal sesamoidean impar ligament, navicular bursa, or navicular collateral ligament pathology