Complete disruption of the palmar / plantar soft tissue periarticular support structures of the pastern results in palmar / plantar luxation and instability.
The horses present as acute onset, and severe lameness, accompanied by instability of the digit. Localizing signs include mild to moderate soft-tissue swelling in conjunction with pain and instability of the pastern region.
All breeds can be affected, but horses engaged in Western performance activities may be overrepresented.
Degenerative disease of the proximal interphalangeal joint as well as fractures of the middle phalanx are seen in most breeds of horses. However horses engaged in western performance activities seem predisposed to injuries involving the proximal interphalangeal joint, especially fractures of the middle phalanx, likely due to the bending and torsional forces generated during abrupt stops and changes in direction.
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Radiographic evaluation of the pastern region reveals malalignment of the proximal interphalangeal joint with palmar/plantar displacement of the distal end of the proximal phalanx.