What are Digital Sheath Tenosynovitis?
This often occurs bilaterally and causes little complications for the horse. In some cases, this condition will affect the horse asymmetrically, which can lead to swelling, pain and lameness. This condition can worsen rapidly and cause irreversible damage to the tendons, therefore if you are concerned that your horse may be displaying these symptoms contact your veterinarian.
Tenosynovitis is a condition that commonly affects working horses. This is the inflammation of the synovial membrane of the digital flexor tendon sheath. This structure encompasses both the superficial and deep digital flexors in the horse.
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Symptoms of Digital Sheath Tenosynovitis in Horses
Tenosynovitis can often be seen through visual examination, in horses that present with pain caused by this condition one sheath may be noticeably larger than the other. Other symptoms that may be seen are:
- Lameness, particularly following exercise (the degree of lameness may vary)
- Pain shown on firm flexion on the limb
- In cases of acute aseptic tenosynovitis rapid, unilateral onset may be seen along with heat and pain on palpation
- In chronic aseptic cases, compromised function with reduced range of motion, lameness after exercise and pain may be seen
- In septic cases, a point of bacterial entry may be seen such as a wound or puncture; cellulitis may also be seen at this site
Causes of Digital Sheath Tenosynovitis in Horses
Tenosynovitis is the swelling of the digital sheath that surrounds the superficial and deep flexor tendons in the leg of the horse. This condition can cause severe inflammation and swelling in horses and can lead to lameness. There are four classifications of tenosynovitis in horses. These are:
- Stage 1 – Unilateral or bilateral fore or hind limb digital sheaths that have a moderate level of fluid in the affected area, however the horse does not show signs of severe lameness
- Stage 2 – Horses suffering from this may show mild to medium signs of lameness, that is often intermittent and may only affect one limb
- Stage 3 – The horse may suffer from consistent, moderate lameness due to inflammation and synovial proliferation; in this stage of the disease damage to the tendons may also occur
- Septic digital sheath – This may cause the horse significant pain and lameness; often horses suffering from this form of the condition will be non weight-bearing on the affected limb and will not tolerate flexion of the fetlock
Diagnosis of Digital Sheath Tenosynovitis in Horses
Your veterinarian will perform a full clinical examination on your horse. In order to assess their gait, she may observe your horse from a distance prior to exercising them to watch for change in the stance. Your veterinarian may watch for contributing factors such as uneven heel height and foot imbalance.
Ultrasonography may be utilized to visualise the digital sheath, this may show varying degrees of distension of the sheath with fluid depending on the stage of the disease. Proliferative tissue may also be seen covering the tendons, with adhesions to the tendons and sheath wall seen in severe cases. In septic cases of tenosynovitis, highly cellular fluid may be seen on ultrasound, with visible adhesions. Your veterinarian may choose to perform a fine needle aspirate using the ultrasound for guidance to collect a sample of the synovial fluid for culture and sensitivity testing.
Treatment of Digital Sheath Tenosynovitis in Horses
If your horse has been diagnosed with Stage 1 or Stage 2 tenosynovitis, your horse may require 2-3 weeks of anti-inflammatory medication to help control pain and inflammation. Other treatments that may be used are:
- Icing and cold hosing of the affected site
- Assessment of shoeing and corrective shoeing provided if needed
- Dietary supplementation of oral glucosamine and hyaluronic acid
If these treatments are ineffective for a horse suffering from stage 1 or 2 tenosynovitis, tenoscopy may be considered. This procedure involves the removal of excess proliferative synovial tissue. For horses suffering from stage 3 tenosynovitis all of these treatments may be commenced immediately. Steroid injections may also be recommended for your horse, particularly following tenoscopy treatment.
If your horse is suffering from septic tenosynovitis they will require systemic antibiotic therapy. Your veterinarian will select the most appropriate antibiotic treatment using the results of the culture and sensitivity. Your veterinarian may also perform a tenoscopy and flush the sheath in order to remove any debris from the site.
Recovery of Digital Sheath Tenosynovitis in Horses
The prognosis for horses suffering from this condition varies depending on a number of factors, including the degree of tendon involvement and the speed of which diagnosis and treatment is given. For horses with stage 1 tenosynovitis, the prognosis for full recovery is excellent, for horses of stage 2 tenosynovitis or who have suffered from small levels of damage to the tendons prognosis may be fair to good, however, a recovery period of 6-8 months should be expected. Unfortunately, for horses that suffer from stage 3 or septic tenosynovitis the prognosis for full recovery may be guarded.
In order to support your horse’s recovery, it is vital that your horse’s return to exercise is carefully monitored, too rapid return can cause treatment to fail.
Digital Sheath Tenosynovitis Questions and Advice from Veterinary Professionals
Hi, my mare suffered a nasty rope burn on near hind beneath fetlock. I didn't realize that the tendon sheath was lacerated and 4 days later the leg became swollen and hot. Vet was called and next morning the leg was operated on, it had become seriously infected and required flushing. My horse is still in 'horsepital', she had been improving but today she is lame on the leg again. Apparently this happens as wound closes adnd pressure builds. Hoping it is not infected again. Praying for a good outcome.
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Hi My 12 yr old cob was diagnosed with tenosynovitis in near hind 6 weeks ago and had a scan which did not show any tendon involvement. He received a cortisone injection and was sound after this. He started exercise last week and is now very slightly lame but quite lame on first few strides after standing in stable. He has no pain on palpitation and farrier found no response to flexing fetlock when shoeing him., He stands in during day and is out with friend at night and both calm. He comes in sound from the field. Any ideas or advice would be welcome. Thanks.
Tenosynovitis and related inflammation may cause swelling, adhesions and tears in ligaments and sheaths which may he difficult to detect by ultrasound. Given the timeframe since the last examination, it may be worth having another ultrasound after stable rest to see if there is any new pathology seen on the ultrasound. The use of supplements like hyaluronic acid are controversial with some saying that hyaluronic acid is ineffective if taken orally. Regards Dr Callum Turner DVM
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