Joints and Soundness
By Linda Kennard of NAF
Traumatic injuries and degenerative disease in the lower limb are some of the most commonly cited reasons for loss of use in the modern sports horse. These conditions can become particularly prevalent during the summer months when the hard ground can increase the concussive forces placed on the limb. One of the most susceptible areas for injury is the joints.
Joints appear in the skeleton where bones meet. This then allows the skeleton flexibility and movement. The basic structure of all joints is similar and comprise of 2 layers:
1. An outer fibrous layer which is attached to the periosteum of the bone. The periosteum is connective tissue which surrounds compact bone and acts as an attachment point for tendons and ligaments.
2. An inner synovial membrane which secretes synovial fluid. This supplies nutrients to the articular cartilage as well as acting as a joint lubrication.
There are three different types of joints fibrous, cartilaginous and synovial.
• Fibrous joints are those less likely to be affected by disease as they are more or less immobile. These are the joints in the skull or the joints between the shafts of some of the long bones.
• Cartilaginous joints are the joints of the pelvis and vertebrae as well as the growth plates. Also because of limited movement risk of disease is reduced.
• Synovial joints are the most likely joints to suffer disease injury. These are the most active joints in the horse’s body. The synovial joints consist of two bone ends covered by articular cartilage. This cartilage within the joint is smooth and resilient and when properly lubricated allows frictionless movement of the joint. The joints stability is maintained by a fibrous joint capsule and the collateral ligaments attached to both bones. Joints such as the fetlock, knee, hock and stifle joint.
JOINT PROBLEMS
Joint problems can arise when there is a fault within the cartilage structure. This can sometimes be seen in rapidly growing young stock or is the result of wear and tear especially in the performance horse. Problems in the older horse involve changes to the articular cartilage.
Bog Spavin – is the swelling of the joint capsule of the hock. This tends to occur in young horses just starting work or in horses with poor conformation.
Ringbone – can occur on any of the limbs but is more common in the forelimb. Ringbone can be divided into different types;
High articular ringbone is the degenerative joint disease of the pastern joint.
Low articular ringbone is the degenerative joint disease of the coffin bone.
There is also false non-articular ringbone. This is when new bone develops on the long pastern, short pastern or the pedal bone but does not interfere with the joint.
Ringbone is seen as a hard swelling in the pastern region. With non atricular or false ringbone once the inflammation has settled horses usually become sound.
Bone Spavin – is a degenerative disease of the hock joint. This is mainly caused by hard work or poor conformation. Horses that jump or make sharp turns tend to be more susceptible. It is wear and tear on the joint and surrounding ligaments.
Degenerative Joint Disease (DJD) – this is where the production of enzymes and prostaglandins break down the cartilage causing it to become thin and ulcerated. As the cartilage thins this increases bone to bone concussion and injury to the joint.
All joints are unique and will respond to injury in different ways. This can make it difficult for the horse owner to spot early signs of joint disease. Early signs may include heat or swelling in and around the joint, pain on flexion and possible varying degrees of lameness.
The horses joints have been designed to absorb shock, allow frictionless movement and effectively bear the weight of a body that can weigh anywhere from 350-650kgs or more. But whatever level you ride at or whatever discipline you take part in, it is imperative that your horse’s musculoskeletal system is conditioned to deal with the workload being placed on him.
For more information about joint health and flexibility please call the NAF Freephone Advice Line:
0800 373 106 or email info@naf-uk.com
