All About ... Joints.

Last week I posted a blog about Bones, this is really only part of the story in understanding what can go wrong as many lameness problems are due to joints or muscle injury.  This week I thought I would look in a bit more detail at joints.

The joints are where bones meet.  Some of the 'meeting places' will have movement and some won't - like the bones in the skull.  

 

There are also different types of joint, defined by the amount of movement they allow and their structure.

Fibrous Joints:- hold bones tightly together with short tough connective tissue.  There is no movement.   Examples include the bones of the skull.

Cartilaginous Joints:- are held together by cartilage!  For example the spine.

Synovial Joints:- these contain a fluid filled cavity which ensures they move freely in one or  more direction.  Synovial fluid is the reason that joints should not be poulticed - the poultice will draw out the fluid which will adversely affect the joint!

Synovial Joints

Most joints are synovial.  The ends of the bones are made up of layers of compact bone which are then covered in hyaline (articular) cartilage.  This is smooth and ensures a smooth, slippery surface for easy movement.  The cartilage also acts as a shock absorber and a joint lubricant.  The spaces between the bones make up the joints and this is surrounded by the joint capsule.  This capsule is made up of the  synovial membrane which is a deep layer and produces the synovial fluid and the fibrous membrane on the surface.   
Ligaments hold the bones together and stabilise the joint.  

There are also different types of synovial joints, which are named according to the movement they can make:

• Hinge joints(ginglymus) - only extension and flexion  - eg: the elbow. 
• Pivot joints (trochoid)- allow shaking movements - eg: the atlas & axis (first 2 cervical vertebrae) 
• Ball & Socket Joints (spheriod) - allow movement in any direction.  One bone has a round head which fits into a cup on the other bone - eg: the shoulder 
• Plane Joints (arthroidal) - allow sliding and gliding movement - eg: the bones within the knee or hock.

Types of Joint Movement

• Flexion of a joint decreases the angle of a joint eg: when bending the knee. 
• Extension increases the angle of a joint eg: when straightening the leg. 
• Rotating is a twisting motion around an axis (or central point). 
• Adduction is the movement of a leg towards the body. 
• Abduction is the movement of a leg away from the body. 
• Gliding or sliding is the movement between the opposing surfaces of arthroidal joints.

Joints in Detail

Shoulder :- formed by the scapula and humerus this is a spheroid joint.  There are few ligaments as the joint is stabilised by muscles.  The muscles restrict the movement allowed to extension, flexion and a small amount of abduction and adduction.

Elbow: - is formed by the humerus and radius & ulna.  This is a ginglymus joint which only allows flexion and extension.  Collateral ligaments hold the elbow in position with muscles.

Knee(Carpus):- is made up of more than one joint and several carpal bones.  It is also a ginglymus joint and has a large joint capsule which runs from the radius to the large metacarpal and surrounds all the structures of the carpus.  The knee has extensive ligaments inside and outside, during flexion the ligaments relax and the foot will turn out slightly.  This joint corresponds to the human wrist.

Fetlock:- is formed by the large metacarpal and the first (proximal) phalanx.  Another ginglymus joint it is hyper-extended when in a normal standing position.  The large joint capsule allows greater flexibility and this joint is supported by suspensory apparatus. This joint is subjected to the greatest stress of any of the joints of the limbs!

 

Pastern:- also called the proximal interphalangeal joint, it is formed by the first (proximal) and second (medial) phalanx .  Again a ginglymus joint there is restricted action and it is also extended when the horse is in a normal standing position.  The extensor tendons limit the flexion of this joint. 

Coffin:- this is formed by the second (medial) and third (distal) phalanx and is located inside the hoof.  Also called the distal interphalangeal joint it allows a great deal of movement.  The suspensory navicular ligament supports the foot and the distal navicular ligament supports the distal sesamoid, attaching it to the distal phalanx.  This joint is again in extension when the horse is standing!  Over extension of this joint is prevented by the suspensory apparatus and the deep digital flexor tendon.

Hock:- is a complex joint , like the knee it is made up of a number of bones,  but is another ginglymus.  It is held in place by the medial and lateral collateral ligament.  The calcaneus (the bone which sticks out) acts as a lever for the attachment of the tendons and it is attached to the remaining tarsal bones by ligaments.  The front of the hock has fewer ligaments.  The hock corresponds with the human ankle.

Stifle: this joint is in 2 parts.  The femurorbital articulation is formed by the tibia and femur.  It is held together by several ligaments.  The fermuropatellar articulation is formed between the patella and the femur.  This is a gingylmus joint allowing extension and flexion although extension is limited bu the ligaments.  This joint corresponds with the human knee.

Hip: is formed by the femur and acetabulum and is a spheroid joint.  The acetabulum is the cup shaped cavity.  This joint also has extensive ligaments.  The acetabulum has no articular cartilage!  The universal movement which is possible with a spheroid joint is limited in the hip by the accessory ligament.

Sacro-iliac: this joint is formed between the axial and appendicular skeleton - the sacrum and wing of the ilium.   This joint is held together by strong ligaments and there is limited movement possible to prevent damage to the nerves. 

Vertebral column: the vertebrae are joined together by fibrocartilaginous discs between the vertebrae bodies.  There is some movement allowed in any direction as the articular processes of each vertebrae form sliding joints.  The largest are in the head region and they decrease in size until they become fused in the sacral area.

Next week I will look at Muscles in more detail, followed by Tendons and Ligaments!

 

Did you see Wednesday's video 'New Rugs!'   on my You Tube channel?

Horse Life and Love.   Please check it out and SUBSCRIBE.

You can also follow me on Facebook and Instagram for updates on Chesney, Basil, Tommy and Daisy.

Until next time!

Jo

My gorgeous boys xx

 

 

Have you seen yesterday's video yet 'New Rugs!' on my You Tube channel.   

Horse Life and Love.  Please check it out and SUBSCRIBE.

You can also follow me on Facebook and Instagram for updates on Chesney, Basil, Tommy and Daisy.

Until next time!

Jo

 

Using Hawthorn as a Herb

This makes up much of the hedges around my field and lots of other fields around the UK.  Also found in Europe and the U.S.   White flowers cover it in the Spring but it is the berries that you want, if you can get them before the birds!

 

Since I have been writing these blogs I have discovered that there are a lot of herbs that could help Basil and his digestion - this is another one!  Chesney seems to enjoy eating this from  the hedge so they are all able to choose this if they need it.

Actions:
See my herb blog for the meanings of these.
 Antispasmodic, Astringent, Cardiac, Diuretic, Sedative, Tonic.

It must not be fed to pregnant mares.

Part Used:
Berries.

Usage:
As a heart tonic, to aid digestion and for lowering high blood pressure.  

Dosage:
15 - 20gms added to feed daily.

Look out for my new video tomorrow on my You Tube channel.   Horse Life and Love
Please check it out and SUBSCRIBE.

You can also follow me on Facebook and Instagram for updates on Chesney, Basil, Tommy and Daisy.

Until next time!

Jo

Chesney Update

Last Autumn Chesney suddenly lost a lot of weight (see my blog here) which was obviously a worrying time.  It has taken almost a year to get him back to a good weight but I think we are finally there :)

Chesney is now 21 years old and is a BIG horse at about 17.1hh.  He has always eaten huge amounts of hay and not needed much hard feed. He has also always had some sugarbeet with his alfalfa feed during the winter just to help keep the weight on him.  

When he started losing weight last year I obviously increased his feed and sugarbeet and following the blood test results put him on a supplement.  After his follow up blood test the vet advised stopping the supplement because everything had balanced out.

Putting weight back on him however has proved much more difficult than I had imagined and has taken much, much longer than I expected.  Chesney has had sugarbeet and oil in his feed nearly constantly since last Autumn (except for about 8 weeks in June/July) .  I also started him on some concentrates at the end of last year.  He has only been fed an alfalfa based feed for many years now but this no longer seemed to be keeping the weight on him.  After looking into this more and writing my 'Caring for the Older Horse' blog I decided that he may not be digesting and utilising his feed so well as he used to.  So I decided that he needed to have a cube or mix to get the Carbohydrates, Proteins, Fats, Vitamins and Minerals into his system more easily.  He has been having a cube designed for older horses and this is, I think, what has really made the difference.  It has been slow but he has gradually rebuilt the muscle and replaced the fat that he lost this time last year.

I did not expect it to be so difficult to replace his weight, considering how quickly he lost it.  The summer grass has helped but not made as rapid a weight increase as I had hoped.  When everyone else is trying to keep their horses from becoming too fat (as I am with Basil and Tommy) I have been trying to get Chesney to eat as much grass as possible!   I just have to hope that the same thing won't happen this year.

Did you see last week's video yet my 'October vlog'    Horse Life and Love
Please check it out and SUBSCRIBE.

You can also follow me on Facebook for updates on Chesney, Basil, Tommy  and Daisy.

Until next time!

Jo

All About The Skeleton and Bones

As you will know from my Anatomy blog horses have about 205 bones in their bodies.  To understand how to look after them and what can go wrong it is useful to understand a bit about the function of the skeleton and the composition of bone.  

The skeleton is a framework of bone and cartilage found within the body tissue it:

• gives the body it's shape and posture 
• allows movement through the action of joints and by providing attachment for the muscles 
• protects internal organs 
• assists with breathing (the ribs) 
• produces red blood cells (in the bone marrow) 
• acts as a reservoir for calcium and phosphorus 

Functional Anatomy
(see my Anatomy blog)

•  The skull is large to accommodate the jaw as the horse is a grazer.  However, it is also to balance the weight of the abdomen.  When moved with the neck it allows the horse to alter his centre of gravity. 

• The spine comprises the cervical, thoracic, lumbar, sacral and coccygeal vertebrae.  The cervical vertebrae allow lateral movement and curvature.  Arching of the neck is mostly movement of the muscles!  The thoracic vertebrae attach to the ribs and any movement is limited.  The lumbar vertebrae do have the ability for slight lateral movement but become more fixed with age.  The sacral vertebrae are fused.  Side to side movement  is obvious at the walk but at faster paces the muscles resist this and make the spinal column rigid thus eliminating the wasteful sideways movements. In addition, muscles above and below the spine prevent it 'rounding' as in cats and dogs. 
• The scapula is large and flat and allows the attachment of the forelimb to the trunk by muscles and ligaments.  Horses do not have collar bones (clavicle) which means that the forelimbs are less restricted. 
• The humerus, radius and ulna are all heavily muscled. 
• The carpus has 7 (or 8) carpal bones which are arranged in 2 rows.  These little bones mean there are several surfaces, this allows for more concussion absorption. 
• The hindlimb is directly attached to the spine this means that any concussive forces will go to the spine and not the limb causing the potential for back problems rather than hind limb problems. 
• The pelvis (ilium, ischium and pubis) provides extensive areas for muscle attachment. 
• The femur is very strong but can be shattered by uncoordinated muscle movement.   Hip problems are usually as a result of rotation or muscle spasm and not the femur being out of place!

Bones

Bone appears to be hard and inelastic but it is actually dynamic and is able to respond to changes in the environment - it is affected by nutrition and stress.  Bone is made up of living material which can grow with the horse.   Some adaption occurs before birth.  In the embryo the skeletal material is cartilage, this is mostly replaced by bone as the horse becomes an adult. Cartilage will remain where firmness is needed but also some flexibility such as the ends of bones and the rings of the trachea and larynx.

There are different types of bone and bones also vary in size and shape depending on their functional requirements.    

Compact bone is much harder and denser and forms the main bulk of the shafts of long bones.  In the long bones it has a large central cavity filled with yellow bone marrow.  This bone marrow produces white blood cells (see my Immune system blog). In other bones the compact bone has tiny spaces.  Spongy (cancellous) bone is made up of a network of hard bars and larger spaces filled with red bone marrow.    Short bones are made up of spongy bone as are the ends of long bones.  The combination of the two types of bone and the spaces mean that the bones can be both strong and hard but also light!  Bone is resistant to 'squashing' forces but weak under 'pulling' forces.  Therefore it is great for support.

Bone also contains nerves, blood and lymph vessels.  New bone can be laid down and also in contrast the size of bones can be reduced.  

Functional Anatomy of Bone

Mature bones are made up of cells called osteocytes, these are surrounded by the intercellular matrix.  The cells are located in spaces (called lacunae) which are connected by small canals (canaliculi) which transmit tissue fluid containing the nutritional needs of the bone cells.  The entire bone is covered by a protective membrane (called the periosteum)which also assists with the transport of nutrients and serves as an attachment for tendons and ligaments.

New bone cells are formed by special cells called osteoblasts, these are capable of rapid division.  Most initial modification of bone occurs before the age of 3 months - called modelling.  Remodelling involves cell turnover.  The first steps of this involve weakening the area further by excavating a tunnel using osteoclasts (which dissolve old bone cells).  This then allows the transport of nutrients and materials required for rebuilding to the area.  The osteoblasts will then form new bone cells.  Obviously this means that bones are WEAKER before they become stronger so applying further stress at this time may lead to a stress fracture!


Growth of Long Bones

The diameter of bones is increased by osteoblast action within the periosteum, the length is increased as cartilage is converted to bone.  Cartilage is then replaced within the epiphyseal (growth) plate. The growth plates of bones  stop 'growing' at different times.  Problems can occur if growth is too rapid or one side grows more rapidly than the other.

The development, modelling and remodelling of bone should be taken into consideration in youngsters and horses recovering from injury.  Even a knock can cause changes to the bone and nutrition can affect the health and strength of them.  Basil has 'new' bone which has formed around the area affected by his tooth abscess - something you would perhaps not think would happen in a horse of 14!

Have you seen my 'October vlog' yet? Horse Life and Love
Please check it out and SUBSCRIBE.

You can also follow me on Facebook and Instagram for updates on Chesney, Basil, Tommy and Daisy.

Until next time!

Jo