Sometimes most of the swelling comes from a large blood pocket within the tendon. The important thing that ultrasound shows, however, is just how much tearing of the tendon has occurred and how large the core lesion is. These tendons glide within a sheath, with normal lubrication to allow for easy movement. Tendinitis will often cause adhesions to form between the tendon and its sheath. One of the primary concerns early on is to prevent these adhesions as much as possible.
Some veterinarians like to inject drugs in the sheath or in the tendon itself.
Hyaluronic acid is expensive but popular. Several years ago the famous veterinary surgeon, Dr. Larry Bramlage, began to do a new type of surgery on horses with bowed tendons. He transected the accessory ligament of the superficial digital flexor tendon. This is known as a check ligament. When it is cut it reduces the strain of the superficial flexor tendon, allowing it a better chance to heal.