Fetlock ring syndrome

Primary ring ligament syndrome

Primary annular ligament syndrome is initially a disease of the fetlock annular ligament. When the annular ligament is shortened or thickened, it puts pressure on the superficial flexor tendon and its tendon sheath. The superficial flexor tendon can become necrotic from the pressure, i.e. superficial parts of the tendon die and the tendon fibres up. The tendon sheath can also become irritated and an inflammation of the tendon sheath develops. This is then increasingly filled, but can only bulge above and below the annular ligament, so that an “hourglass-shaped” constriction of the tendon sheath by the annular ligament becomes visible.

Secondary ring ligament syndrome

In secondary annular ligament syndrome, the flexor tendons are initially inflamed and also thickened due to the inflammation. However, the annular ligament is not elastic and cannot give way to the thickened tendon area. Therefore, the thickened tendons are constricted in the area of the annular ligament and can thus be additionally damaged. The tendon sheaths are always affected at the same time, as they are also squeezed by the tightness in the ring ligament area.

Both forms of fetlock ring syndrome often lead to adhesions between the structures involved. These severely restrict mobility in this area. In most cases, only a surgical cutting of the ring ligament can help to bring the disease to a halt, to loosen the adhesions and to prevent further tendon damage and possibly the euthanasia of the animal.