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Joints

About Joints and how to keep your Horse sound
By Walter Berger ADip AppSc (H. Mgt)

There is an old proverb that goes something like "no foot, no horse". You could often also say "no joint, no horse". This would be especially true for performance horses, where any joint problems could be detrimental. All in all horses are remarkably adaptable and will often compensate for small problems in an area without us knowing about it. That is until the problem gets worse, or we expect more of the horse to a degree where the horse cannot compensate any more. Then you could end up with anything from a lack of willingness on the horses behalf, reduced speed or ability to jump, to severe lameness.

With some knowledge, forethought and care, many of these problems can be avoided or reduced.

TYPES AND CONSTRUCTION OF JOINTS

First a quick lesson on joints. The three main types of joints are.

            1.         Fibrous joints, which are fixed (eg. skull).
            2.         Cartilaginous joints, which may have some movement (eg. spine).
            3.         Synovial joints, which are mobile joints (eg. knee).

The Synovial joints are the ones, which most often cause us difficulties with horses. Following is a brief description of the parts that make up a Synovial joint.

In a Synovial joint, the ends of the bone are covered by articular cartilage. The two bones are joined together by the collateral ligaments and the joint capsule. These are attached to the periosteum, a thin but tough fibrous membrane to which tendons and ligaments may attach themselves. The joint capsule consists of a fibrous outer layer and the inner layer, the synovial membrane. The joint capsule contains within it synovial fluid.

  Synovial JointFig 1. Synovial Joint

       Articular Cartilage – A strong, semi-elastic tissue and serves to protect the bone ends it is attached to. It has no nerves or blood supply and has limited powers of regeneration. For nutrition cartilage is reliant on the synovial fluid.

      Collateral Ligament – Its purpose is to limit the movement of the joint. The ligaments are flexible but relatively inelastic. There are both medial and lateral ligaments.

      Joint Capsule – A fibrous outer layer serves to limit the movement of the joint it protects. It contains the synovial cavity.

      Periosteum – A thin but tough fibrous membrane to which tendons and ligaments may attach themselves.

      Synovial Membrane – Has a rich supply of nerves and blood to it. The nerve supply is there to prevent damage to the joint. The cells of the synovial membrane secrete hyaluronic acid, a component of synovial fluid.

      Synovial Fluid – The synovial membrane controls its composition. It is crucial to the health of the joint. It consists of some of the constituents of blood and hyaluronic acid.  Hyaluronic acid's purpose is to aid in the nutrition and lubrication of the cartilage. Synovial fluid provides cushioning of the joint, lubrication to the cartilages and the synovial membranes and provides nutrition to the cartilage. The supply of nutrients to the cartilages is controlled by the amount of movement of the synovial fluid. If movement of the joint is restricted, so is the movement of the fluid through the joint. This can result in insufficient nutrients getting to the cartilage, which can then result in cell death and damage to the cartilage. As mentioned previously, the cartilage has limited powers of regeneration, so any damage is usually not repaired completely but may not cause any obvious effects. (Rossdale,1987), (Frandson & Spurgeon ,1992).          

Basically all the components are designed to work together, to hold the joint together while permitting smooth, lubricated motion without letting things move too far. All this motion is controlled by muscles including back and neck muscles and, in the lower legs, tendons. All of the leg structure is designed to support the horse and to help absorb the many shocks involved with the horse’s movement.

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CAUSE OF PROBLEMS AND PREVENTION

There are (unfortunately) many problems which can affect the equine joint. They range from old age, wear and tear, to arthritic problems and traumatic injuries. Sometimes damage to surrounding and connecting tissues such as ligaments, tendons and muscles lead to a joint experiencing abnormal wear, which can lead to problems down the track. So we have to try to protect the whole horse in order to protect the joint.

While we cannot prevent everything that causes problems, there are things we can do to reduce the number and severity of incidents.

       Nutrition – Proper nutrition, especially of the younger horse, is important. Overfeeding the young horse can be as bad as underfeeding as the developing joints, tendons and ligaments may not have the strength to support an obese youngster. This can cause problems later on in life, especially for a horse destined for some sort of athletic career. Of course all horses regardless of age need the correct balance of minerals, energy, protein etc.

       Warm Up – Warm up your horse properly. About the worst thing you could do is work a horse hard, stick him (or her) in a box overnight and then drag him out the morning after and get straight into it again when he is already stiff from the day before. Age, the horses condition and fitness and intended work all need to be taken into account for the warm up. Start with a walk, take your time and progress from there. You can even use massage and stretching as part as your warm up routine. This could help with recognising any particular problems before they worsen.

       Foot Maintenance – The shape of the horses foot impacts lots of things. It can affect the flight path of the hoof through the air before it touches the ground again; the amount of time the foot is in the air; the whole geometry of the lower leg and the shock absorbing properties of it. Most horses need regular trimming of the hoof as it grows to maintain a proper shape, regardless wether it is shod or going barefoot. This could also reduce the chances of hoofs cracking.

There are so many different schools of thought on the subject of horse’s feet, that I will not go deeply into it. Every horse is different, even though the fundamentals are the same. Basically the geometry of the foot needs to be correct for the horse in question. If you perceive there to be a problem, try something or somebody else. But give it time to work. It may take anything from three to 12 months to get things right. If you change too much too quickly you could cause extra discomfort to the horse.

       Conditioning – A horse needs to be fit for the task that is set him. If he only goes for a short leisurely trail ride once a month, walking around a paddock will keep him fit enough for that. You would not expect a horse, which has just spent a couple of months in a paddock to win the Melbourne cup. But then again you would not expect a Melbourne Cup winner to do a dressage test, especially a harder one, as muscles are used in a different way. Racehorses do not tend to show or use much collection. Also you would not take a fit dressage horse, which is only used to soft footing, on an endurance ride with rocky tracks or hard roads.

The Muscles, bones ligaments and tendons of the horse take months to adapt properly to new types of work. An endurance horse is taken for slow (read walk, maybe some trot) work for months before proceeding to faster longer work. All this actually increases bone mass and strengthens connective tissues. A dressage horse also takes months to build up muscle mass over its back and neck to enable it to round up and carry itself. Similar with eventer, jumpers and hunters. Time and patience is important.

       Protection – Due to the weight and stresses imposed on horses during normal activities, and things we ask him to do for us, there is minimal protection we can provide. We can provide him with a variety of boots to protect him from bumps knocks and scrapes. Some help to protect and support the tendons at the back of the leg. Others provide minimal support but help to keep warmth in. Some of the Neoprene type boots (no names mentioned here unless I get some freebies) claim to provide measurable impact absorption, support and protect tendons, and even help with the rebound. Just like a good pair of runners. They also help with heat retention. Heat retention can be a good thing as it improves blood circulation, which supplies nutrients and removes waste products, and can help to supple stiff areas.

While the protection provided by these means may not be great, they can be better than nothing. But they have to be used properly, or you can severely injure your horse by meaning well. Tendons are easily damaged by boots that are too tight, hard edges have to be watched out for, and skin be allowed to breath free of rubber or plastic boots at times.

       Footing – While horses seem to cope well running around rough paddocks, it does take its toll. Take your horse too many times at too fast a pace over rough tracks and wear and tear will set in. In an ideal world all tracks would look like a lush racecourse. But they do not, and the lower part of the horses leg absorbs most of it. Eventually all these near sprains and strains may cause arthritic and other problems to appear, often in the fetlock joints.

You can take care to avoid rough tracks, or at least take it easy, but what about the hard or slippery ones? For hard footing, see conditioning. If a horse that has been used to work in soft arenas and resting in grassy paddocks is to be used seriously on hard surfaces, it will take time for him to become conditioned to it.

Most horsy people would have experienced walking in muddy paddocks or laneways, and know how unexpected slips jar the body. Same with horses. Using studs on shoes for working or competition horses can help this, but this has to be done carefully. A horse’s foot is meant to move slightly on landing or takeoff. In the USA the J.D. Wheat Veterinary Orthopedic Research Laboratory has done some research with racehorses along these lines. This has shown that horses, which use shoes with toe grabs, are twice as likely to develop problems with the suspensory apparatus than horses that do not. Therefore if studs are used, they have to give enough grip to the horse without actually anchoring the foot firmly to the ground in order to avoid long term problems.

       Supplements and Drugs – Now here is a kettle of fish. There are a large variety of Vitamins, Minerals, Herbs, Drugs, chemicals and Nutraceuticals available. Some reduce pain or inflammation, or claim to. Some are supposed to help repair damaged tissue, or just generally complement a horses lifestyle or diet. I will just mention a couple here that are used for joint problems in horses, and have proven effects. Other drugs such as Pentosan Sulfate or Hyaluronic acid may also be used to improve joint function and aid in healing, but these are injectables and not usually available to untrained persons.

As always if you are thinking of giving your horse anything that you are not sure of seek professional advice.

      Phenylbutazone (Bute) must be one of the more common drugs given to a horse, but the use of Bute can be controversial. A study by staff of The Ohio State University’s (OSU) Orthopedic Research Laboratory has shown that the use of Bute and other non-steroidal anti-inflammatory medications (NSAIDS) could be detrimental to the regeneration of cartilage in horse. This is because Bute appeared to block the production of some building blocks of cartilage and that some inflammation is part of the natural healing process. A previous OSU study published in May of 2000 also reported that Bute suppressed bone formation and healing. This is in addition to other possible know long-term side effects such as stomach ulcers. All this said Bute can be a very useful substance if used correctly to manage injuries or chronic conditions. As mentioned before, if in doubt get advice or a second opinion if you do not like the first one.

      Specific joint supplements and treatments are becoming more popular. These often use some of the precursors or building blocks used for cartilage production, such as glucosamine and chondroitin sulfate. David Ramey, DVM, In his book, Consumer's Guide to Alternative Therapies in the Horse (Howell, 1999) writes, "Research indicates that glucosamine may have some promising anti-inflammatory and joint protective effects, particularly if used early in the treatment of arthritis." Also in an article called “Will Medicine Keep Your Horse Sound?” by R. Reid Hanson, DVM, Dipl. ACVS (The Horse, April 1996) it is stated that Studies in Europe concluded the actions of glucosamine salts and chondroitin sulfates are synergistic, and combinations of these therapies have great potential to improve the supply of nutrients to cartilage and thus prevent impairment.

      Another substance called Methylsulfonylmethane (MSM) is often included together with glucosamine and chondroitin supplements. This acts as an inhibitor to the production of substances as a result of inflammation, which can impede the repair of cartilage. This is the result of a study initiated by the Nutraceutical Alliance and was carried out by orthopedic researcher Mark Hurtig, DVM, MVSc, Dipl. ACVS. It is also believed to act as a donor of Sulphur atoms, which is used in the production of cartilage.

From a personal aspect I know my knees seem to function better with these, than without. In studies of both horses and humans these products have been shown to improve cartilage repair or prevent further cartilage degeneration. This together with the anti-inflammatory properties of MSM reduces pain levels, and therefore can increase comfort.

Now that you have all this information, it should give you an idea on how a horse works and how to keep him that way. Most of it comes down to common sense, or you might say, horse sense.

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