Asymmetry

Even if the saddle is a perfect fit, the rider may cause imbalance, with many riders sitting crookedly causing the horse to over compensate.  Misalignments in the rider (especially pelvic) will also affect the way in which they sit.

These asymmetries could easily be passed on to the horse, having an effect upon the musculature that lies beneath the saddle.

Other causes for asymmetry could be due to:

Motion asymmetries during training.

There is a necessity for horses to be worked evenly on both reins.  This reduces both the negative effects that may be caused by the rider and/or horse favouring a particular direction, rein or leading limb.

Horses being led from the left and mounted from the left.  Riders almost always mount their horse from its left side.  This drags the left shoulder, thoracic side down, causing muscle weakness there.  Mounting blocks are highly recommended.

Back pain: muscle wastage (atrophy), limb related lameness (might have significant repercussions on the kinematics of the back).  When a horse becomes lame, the animal tightens up the muscles around the affected limb to guard it from further pain.  In order to stay balanced the horse usually tightens up the area of the back which is on the side diagonally opposed to the injured limb, which can often remain even after the injury has healed.

The conformation, type and use to which horses are put can have an important bearing on the injuries involved.  For example specific spinal malformations (e.g. lordosis and scoliosis) tend to predispose to injury through the inherent weakness of the back arrangement of the thoracolumbar spine.  Horses that are short-backed with restricted flexibility of the spine tend to exhibit more vertebral lesions than longer backed animals.  It is believed that larger framed animals with comparatively weak-looking quarters definitely appear to be more susceptible to sacroiliac problems.

Dental problems or shoeing (limb balance)

Pain or discomfort in the mouth will cause tension at the jaw joint (temporal mandibular joint), which in turn affects the poll, neck and back.  If the teeth are not ground down by natural wear or rasping, the molars and premolars develop sharp points, which can catch on the inside cheeks.  The horse may find it uncomfortable to relax its lower jaw to the pressure of the bit.  Locking of the lower jaw can occur, causing tension in the poll and therefore along the back.  If the horse is uncomfortable for any reason on its feet, whether front or back, in response the muscles tighten in the back, particularly the loins.  This is an attempt to reduce concussion but in effect it reduces the stride and increases the discomfort in the feet.




Poor hoof balance: causing different weight loads up the limb, also affecting flight path of the limb.








Spavin

Bog spavin is first seen as a swelling in two distinct locations at the back and front of the hock joint.  These swellings are where the joint fluid of the top joint of the hock has increased in the sack in which it is contained and pushes out so it becomes visible.  Bog-Spavin normally occurs in horses that have poor conformation and does not cause too much of a problem.  The poor conformation of the joints causes extra fluid to be produced which perhaps makes the joint less liable to get damaged.

Bone Spavin is the common name for Secondary (Degenerative) Joint Disease (Osteo-arthritis) of the Hock.  Bone Spavin is normally evident in both hocks although one may be worse than the other.  Horses will show some stiffness when coming out of the stable in the morning and will also show some irregular paces when doing flatwork.  Often dragging the affected limb and squaring the hind toe.  Radiography is needed to determine the level of damage and both hocks should be scanned.  During the bony changes of a bone spavin a horse may often compensate heavily, particularly if one hind limb is affected rather than both.  This can often affect the hips and lower back.  Often resulting in the unaffected limb later degenerating as the horse compensates onto the better hindleg (more confortable) at that particular time.

Shiverer

Shivering, or shivers as it is also known, is a mysterious and poorly understood disease of the nervous system.  It is characterised by an involuntary elevation of a hindleg which then quivers and shakes, before returning back down.  This makes it very difficult and stressful for the horse to be shod etc.  Shivering tends to become progressively worse, and there is no treatment, although some control of early cases can be achieved with a high fat and low carbohydrate diet.

Stringhalt

Stringhalt is a poorly understood neuromuscular disorder in which the nerves to the muscles are afflicted.  It results in a mild to severe ‘hyper flexion’ (extreme flexing upwards) of one or both hocks.  This is shown as a sudden jerking up of the limb, either occasionally or with every step.  It is most obvious at walk, on turning or on backing up.

Yet most horses remain remarkably unconcerned. The cause of the nerve degeneration is unknown but may be a result of trauma.

Upward Fixation of the Patella

This occurs when the patella (or kneecap) becomes locked causing the characteristic rigid extension of the stifle and hock.  The leg remains like this until the hind-limb muscles are able release the patella and allow the stifle to flex once more.  If a horse is found locked up in this manor it is best to encourage the horse to back up, often releasing the patella thus freeing the limb.  It is usually seen in younger animals in poor condition, especially those with straight hind-limb conformation, or those who are off work and are lacking muscle, common in winter months.

The condition can affect one or both hind-limbs, can be intermittent or permanent, and can vary from mild to severe.  Severe cases tend to be those that lock for long periods of time and milder cases simply slipping off track for literally seconds.  Surgery to cut the inside patella ligament is only now used as a last resort.

Kissing spines

This is known as the impingement of two or more of the dorsal spinous processes (the spinous processes are boney protrusions vertically from the vertebral bodies).  For example, the withers are actually just the huge spinous processes of the forward thoracic vertebrae rising up between the shoulder blades.  The spinous processes may get too close to one another, and begin to rub or to react by forming new bone this can be very painful and can cause the horse to react particularly while under-saddle.  Diagnosis can sometimes be made with ultrasound, though radiography and nuclear scintigraphy (bone scan) are often more beneficial.  Successful treatment can include direct injection of corticosteroids in the area of the lesion, shockwave therapy, or surgery in non-responsive cases (removal of an affected spinous process).