The 11 systems of the horse – The Skeletal System

My aim here is to give you a brief overview of the skeletal system.

What is the Skeletal System made up of?

Most horses have 205 bones in their body.  This can vary slightly as Arabians can have 1 set less of ribs due to a shorter back.  Also the amount of coccygeal or tail bones may vary slightly.  The skeleton is made up of long, short, flat and irregular bones. The long bones are typically found in the limbs - they act like levers and store minerals.  Short bones are found in the fetlock, knee and hocks and their job is to be shock absorbents.  Examples of flat bones are the ribs and scapula and these are there to protect.  And irregular bones protect the central nervous system and are found in vertebrae.  The bones are connected to each other via ligaments and the muscles are connected to the bones via tendons.  A bone is covered in a tough outer layer called the periosteum and at the site of joints there are little bursae sacs filled with synovial fluid which act as cushioning and lubricant of the joints.

What it does?

The function of bones is to provide the body's framework, protect vital organs and protect soft tissue.  Bones also are levers, store minerals and are where red blood cells are formed.  The muscles act to support the entire skeleton of the horse and the stronger these are the better supported the horse's skeleton is.

What can happen to the skeletal system that affects the horses performance?

Horses can suffer from degenerative joint disease (DJD)- typically osteoarthritis which will cause the joints and bones to wear and this will cause pain and a decreases range of movement.  Included here would be things like bone spavin - extra laying down of bone fibres around the hock joint, ringbone - again usually through concussive type activities the body will lay down fibres surrounding the pastern area, given it's name as it will feel like a ring and inflammatory joint disease.  Curb will present as swelling in the hock area and is usually the result of inflammation of the ligaments.  Splints - these are found in the lower limbs and are a result of concussive injury and there can also be a fracture of the metacarpal or metatarsals (kind of extra-ish bones in the front and back lower legs respectively).  The body will lay down fibres over the area to repair the body and this will generally cause thickening of the bone in these areas.  It is a common occurrence in showjumpers and racehorses due to repetitive concussive force.  Other fractures can occur - usually these are life ending.  Navicular disease is occurs through inflammation or degeneration of the navicular bone, surrounding soft tissue and compaction of cartilage which is the cushioning provided in the horses feet.  It is severely debilitating to the horse.

There is a high amount of stress placed on performance horses and horses do not mature in their body until 6 years of age.  Meaning that their joints and bones have not fully formed or completed growing and strengthening until this age.  This also means that sports undertaken with immature horses may compromise it's skeleton early in life and predispose them to DJD and osteoarthritis later on in their careers.

There are a lot of supplements available on the market to help horses joints and some of them are very good.  A few things to remember though are: that no matter how fast we want a horse to mature it will take 6 years to be fully mature in their body and that doesn't vary according to breed and having your horse's bought up to fitness for their jobs needs to be done in a manner that will help to prevent injuries from occurring.

An image of the skeletal system of the horse
  1. Skull
  2. Mandible
  3. Temporomandibular joint TMJ
  4. Vertebral spine
  5. Ribs
  6. Intercostal cartilage
  7. Stenum
  8. Scapula cartilage
  9. Scapula
  10. Humerus
  11. Radius
  12. Elbow Ulna
  13. Carpals
  14. Metacarpal or cannon bone
  15. Sesamoid
  16. 1st phalange (proximal) or long pastern
  17. 2nd phalanx (middle) or short pastern
  18. Navicular
  19. 3rd phalanx (distal) or coffin bone
  20. Illium
  21. Ischium
  22. Pubis
  23. Femur
  24. Patella
  25. Tibia
  26. Fibula
  27. Tarsals
  28. Metatarsal or cannon bone