Blackthorn Penetrations in Horses

The blackthorn (Prunus spinous) is a perennial shrub which occurs commonly in hedgerows and thickets in the Wiltshire area. The shrub bears narrow thorns up to 5cm long which can penetrate a horse’s skin and break off, remaining embedded in the tissues. The blackthorn sets up a rapid foreign body reaction which leads to local heat, swelling and pain within hours. If a blackthorn should penetrate a synovial structure such as a joint or tendon sheath the reaction is often very severe with extreme pain and joint/tendon sheath swelling

Picture of Blackthorn bush/thorn

In many cases the thorn can be identified and removed with a small pair of forceps or tweezers. Care should be taken to avoid breaking off the thorn tip when removing the thorn. Occasionally, poulticing may encourage the thorn to be expelled from the tissues. In the event of a thorn penetrating a joint or tendon sheath this will often require a surgical operation to flush the joint and remove the thorn. Rapid treatment will ensure the best chance of success and if a thorn penetration into a vital structure is suspected then early veterinary attention is vital. If left in the tissues, a blackthorn will often lead to a chronic swelling due to a persistent foreign body reaction.

In 2011 at Endells, a record number of blackthorn injuries were seen, with the most common site of injury the knee, closely followed by the tendon sheath. Several horses were seen with large thorn fragments embedded in the tissues which were removed with ultrasound guidance and a minor (standing) surgical approach.

If you suspect that your horse or pony has suffered a blackthorn penetration, our advice is to examine the area closely to see if a small entry wound is present. Clipping the hair coat may assist in this procedure. If a small fragment is protruding then removal is best done by your veterinary surgeon following an ultrasound examination of the area to determine the size, depth and direction of the thorn, as well as the proximity of vital structures. Blackthorn penetrations into synovial spaces will always cause severe lameness and we would always advise urgent veterinary attention. If the affected joint /tendon sheath is treated quickly then the majority horses make a rapid recovery and are back in work in 4-6 weeks.

Prevention of thorn injuries and their complications is best ensured by avoiding areas of blackthorn if possible, protecting your horse’s legs as far as practical with boots and should your horse suffer an injury, quick diagnosis and treatment.

Photograph of blackthorn fragment inside a fetlock joint