If your horse has crooked legs, this can cause strain on the joints. Because the front legs take more than 60% of the weight when a horse is ridden, problems with these legs are more likely to result in arthritis and lameness than the back legs. If you want to know whether your horse’s front legs are ‘straight’, have the horse stand on even ground. From the side, an imaginary weighted line should go through the centre of the leg, down through the centre of the knee and fetlock and reach the ground a few centimetres behind the back of the hoof.
The ‘knee’ or ‘carpus’ contains a large number of small bones, each linked together with ligaments and encircled by a joint capsule.
If the bone above the knee – the humerus – or the one below – the metacarpal or cannon bone – aren’t in straight alignment with each other, there will be uneven pressure on the carpal bones. This can lead to acute arthritis or, as seen in racehorses, to a fracture of one of the carpal bones. Chronic arthritis of the knee is a common condition among older horses.
The fetlock joint
At the end of the cannon bone you’ll see that the horse’s leg is no longer ‘upright’ – it’s slanted forwards. In-between is the ‘fetlock joint’. This acts as a shock absorber when the horse is moving quickly. There are two small bones at the back of the fetlock. These are the sesamoids and they’re often damaged when a horse over-flexes its fetlock while jumping. The problem is much more likely to occur if the leg as a whole is ‘crooked’, as this will place uneven pressure on these bones.
The coffin joint
From the fetlock to the hoof, two bones – the metacarpals – are involved. The joint in-between can become arthritic and, in chronic cases, a bony ridge known as a ‘ringbone’ builds up. This is often found in horses that have crooked hooves as a result of uneven pressure on the joint.
What can be done?
Prevention – that is, selecting horses with straight front legs – is best. However, very gifted horses may have slightly skew legs and your farrier can do a lot to prevent chronic arthritis by trimming or shoeing them to prevent uneven pressure on the joints further up the legs.
Contact Dr Mac at [email protected]. Please state ‘Horse talk’ in the subject line of your email.