Tendon injuries are extremely common in veterinary practice. They can be due to a strain, laceration or puncture.

Clinical signs

• Swollen leg
• Bowed tendon
• Lameness of varying degrees
• May feel heat in leg

Tendon structure and properties

80% of the tendon is made up of collagen fibres (type 1(95%), 3 and 5 ) and the rest is elastine. The molecular unit of collagen is called tropocollagen. Part of the matrix is viscous and made up of proteoglycans and glycoproteins. The fibres are organised in to bundles and there are vessels in between these. The fibres are crimped. However there is less crimping in the mid-cannon region which means there is less ability for stretching.

Tendon damage can be divided into three phases:

Acute Stage (first few days)

The main process here is inflammation. There is hemorrhage (bleeding) into the damaged area and inflammatory cells enter the area and release enzymes which further damage the tendon. The main clinical signs are lameness, pain, heat and swelling. The amount of lameness does not reflect the amount damage just the amount of inflammation.

Sub acute Stage (weeks to months)

Inflammation reduces and the lameness will subside. As the tendon is still weak there is great potential for re-damaging the same site.

Chronic Stage

The scar tissue matures and re-models. The collagen that replaces the damaged tendon is mainly type 3 which is not as strong or elastic as type 1, therefore there is more chance that the area will be re-damaged in the future. Ultimately, the more type 1 fibrils that are present and aligned in the repaired area the better.

Diagnosis

Diagnosis is based on clinical signs (see above) and palpation of the area. Your vet will then recommend you have an ultrasound scan of the area as this is invaluable to inform them of which structure is damaged and how badly. Ultrasound scans are generally done 7-10 days after the initial injury.

Treatment

Immediately post injury the leg should be cold hosed for a maximum of 20 minutes. The leg should then be dried and a stable bandage applied. The cold hosing and bandaging should be continued on a daily basis as instructed by your Veterinary Surgeon.

The horse must be kept on strict box rest until further notice.

Anti-inflammatories help with reducing the inflammation and therefore the damage as well as make your horse feel more comfortable.

Polysulphated glycosaminoglycans (PSGAGs) can also help reduce enzyme damage and therefore inflammation.

7-10 days later an ultrasound scan can be performed

After the scan there may be further treatments that can be considered for your horse such as stem cell therapy or A cell.

Stem cell therapy is where cells are taken from the bone marrow of your horses sternum and sent away to be grown up. Stem cells are multi potent and can differentiate into many different cell types including new cells in the tendons. These are injected under ultrasound guidance into the damaged area.

A cell therapy involves injecting cells from pigs bladder into the damaged area and this provides a frame work for the horses own stem cells to grow on.

Repeat ultrasound examinations will be carried out at varying periods to assess progress and your Veterinary Surgeon will advise you when to start an increasing exercise programme.

An exercise program will be devised for your horse based on clinical and ultrasonographic signs; below is a typical example:

Weeks 0 -4

Walk out in hand 15 minutes twice a day (if sensible horse)

Weeks 4 -8

Build up the walking by 10 minutes each week

Weeks 12 -16

Add in 10 minutes of trot again increasing each week.

Weeks 16 -24

Turn out included – variable duration

Some horses may need surgery to treat some tendon problems your Veterinary Surgeon will talk to you about these cases as necessary.