Q: I have owned my 12-year-old Thoroughbred mare for six months. Seven weeks ago, she ruptured the peroneus tertius muscle in her off-hind leg while turned out in the field. The treatment prescribed was three to six months’ box rest.

Her lameness is less pronounced now so the healing process seems to be under way. However, I would like to know if there is anything I can do to make her recovery as swift as possible and to ensure the muscle is as strong as it was before the accident happened.

My vet has suggested that physiotherapy or ultrasound could assist in her recuperation.

In addition to this, is there anything else I can do to help – such as walking her in-hand daily – or is it too early to start such exercise? I currently lead her out each day so she can have some grass, but walking is kept to a minimum.

Graeme Cooke MRCVS replies: A ruptured peroneus tertius muscle is a very dramatic injury initially and many people think the horse has actually fractured its limb.

Fortunately, it is easy for an experienced vet to diagnose and X-rays are usually unnecessary. Surprisingly, for such a dramatic condition, the prognosis is usually quite favourable.

However, it is very much dependent on where on the tendon the rupture has taken place.

If the rupture is near the origin or insertion (where it joins the bone) of the tendon, then the prognosis is not good.

Most commonly the rupture is near the hock, and in this case the outlook is optimistic. Your vet may be able to give you an idea as to where the rupture is.

The most crucial part of the treatment is to rest the leg completely for a period of at least eight weeks. After that, a limited amount of controlled walking exercise should be commenced for a minimum of three months.

If instability occurs, there is a high risk that the hock joint may develop arthritis.

The aim of controlled walking exercise is to allow the ordered formation of scar tissue between the ends of the tendon that are ruptured.

Usually at the end of eight weeks your vet will have an idea as to whether the tendon has united sufficiently to give a good outlook.

Most vets would say they could certainly do this by 12 weeks post injury.Your vet has suggested that physiotherapy and ultrasound would be of help. This is very true.

However, ultrasound is particularly beneficial in the early stages and you should consider maintaining physiotherapy from now on.

The most important part of the physiotherapy is the controlled walking. Seek your vet’s advice on this, but normally the exercise regime wouldn’t start until 9-10 weeks after the injury.

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