Eleanor Storey BSc (Hons) BVM&S MRCVS, St David’s Equine Practice
Degenerative joint disease (DJD), also otherwise known as osteoarthritis, is the single most common cause of lameness in horses. Typically DJD is associated with the older horse or pony, however is also very common in the younger performance horse.
A normal synovial joint is composed of two bones that are covered by smooth articular cartilage within the joint. The purpose of the articular cartilage is to be resilient to forces within the joint and also to enable frictionless movement of the joint. The joint also contains a thick fluid, called synovial fluid, which is produced by the synovial membrane and provides lubrication within the joint. The joint is also surrounded by a fibrous articular capsule, collateral ligaments and soft tissues which provide stability to most joints.
Why does degenerative joint disease occur in horses?
DJD occurs as a result of progressive deterioration, or loss, of the articular cartilage and is then often accompanied by changes to the bone and soft tissues of the joint. Deterioration of the articular cartilage can happen as result of:
Abnormal or defective articular cartilage (such as osteochondrosis/OCD in young horses)
Instability of the joint often due to soft tissue injury (such as sprain of the collateral ligaments)
Excessive or repeated overuse of a joint
Trauma to the joint (such as wounds resulting in a bacterial joint infection)
What signs will a horse show if they are affected by degenerative joint disease?
Horses affected by DJD can present in many ways. Competition horses often show signs of poor or reduced performance initially however other horses may have joint swelling or effusion (increased joint fluid within a joint) depending on the stage and severity of disease. DJD is painful and so is often accompanied by lameness during exercise or stiffness after a period of rest.
How is degenerative joint disease diagnosed in horses?
Your vet will initially carry out a full physical examination of your horse, which will include palpating the limbs to feel for any swollen, effused or painful joints. Sometimes pain is only obvious when the joints are flexed and extended. Often your vet will then ask to observe your horse at walk and trot and may carry out flexion tests to further pinpoint the source of lameness. Nerve or joint blocks may then be required to further identify the cause of lameness. Once an area of the limb(s) is suspected then radiographs are frequently taken to investigate further. Ultrasound, scintigraphy (bone scan), MRI and CT can also be used to identify abnormalities if required in certain cases.
All joints can be affected however the most common joints affected are the coffin, front fetlock, hock and stifle joints.
What treatments are available to treat degenerative joint disease?
The main aim of treatment is to reduce pain and minimise further deterioration of the joint. Both medical and surgical treatment options are available. Medical treatment of DJD is the most common approach and treatment options include:
- Oral joint supplements, often containing glucosamine and chondroitin sulphate. We have our own St David’s Equine brand joint supplement available
- Intra-articular corticosteroids – this is the method of injecting corticosteroid into the affected joint(s)
- Hyaluron – this can be administered directly into the affected joint (alongside corticosteroids if required) or intravenously
- Non-steroidal anti-inflammatories (Danilon™/Equipalazone™/Metacam™)
- Pentosan polysulphate, otherwise known as Cartrophen™ – a course of treatment is administered intramuscularly
Surgery is sometimes carried out in certain cases. Often arthroscopy is undertaken if there is a fragment of loose cartilage within the joint and the joint is then thoroughly lavaged (flushed) to remove the substances responsible for inflammation within the joint. A surgery known as arthrodesis may also be required for advanced cases of DJD in non-competition horses to immobilise the joint.
Often a rehabilitation programme is also recommended alongside medical or surgical treatment and may include a controlled exercise programme, adequate foot balance and hoof care and physical therapy as appropriate.
St David’s Equine provides the equine veterinary services for Molecare Veterinary Services. Visit www.stdavids-equine.co.uk for more information.