It arises from a separate ossification center that should radiographically fuse with the olecranon by the time the dog is 20 weeks old. Clinical signs include weight-bearing lameness, joint effusion, joint pain, crepitus, and decreased range of motion. The diagnosis is confirmed radiographically by a radiolucent line between the anconeal and olecranon processes in an animal older than 20 weeks. The underlying pathogenesis of UAP appears to involve incongruous radial and ulnar growth. Treatment options include surgical excision, lag-screw attachment, and proximal ulnar osteotomy.
Initial results seem to favor proximal ulnar osteotomy, but more research is needed.
Early surgical therapy is recommended, but osteoarthritis may persist and progress despite appropriate surgical intervention.