Tendon injuries are extremely common in veterinary practice and can be due to a strain, laceration or puncture.
- 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.
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 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.
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.
Horses with tendon injuries 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 PRP.
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.
Platelet Rich Plasma (PRP) involves collecting your horses own blood and running it through a filtration system to syphon off the platelets and plasma. These carry regenerative growth factors. The PRP is then injected into the core lesion with in the tendon or ligament via ultrasound guidance. The horse is usually sedated for this procedure.
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 for horse with tendon injuries will be devised for your horse based on clinical and ultrasonographic signs; below is a typical example:
Weeks 0 -4
Walk out in hand 20 minutes per day in hand (if sensible horse)
Weeks 4 -12
Build up the duration of the walk by 5 minutes each week
Weeks 12 -16
Add in a few minutes of trot again increasing each week.
Weeks 16 -24
Turn out included – variable duration
Some horses with tendon injuries may need surgery to treat some tendon problems your Veterinary Surgeon will talk to you about these cases as necessary.