Biomechanics Flashcards
Whats the point of the Stay apparatus
How does it work
The Equine Stay Apparatus
Ability to relax and even sleep in a standing position
Ability to stand without a great deal of muscular effort
Allows the horse to be
in constant readiness for flight.
The Equine Stay Apparatus
- The stay apparatus combines a series of Muscles and ligaments that lock the main joints in position
- Horse „pole volts“ over a locked front leg
- Stay apparatus stabilizes the leg in every step the horse does
•The Joints are locked at extension of the front leg.
•At the end of extension, the ligaments stop the
bones from moving
Function of ligaments and tendons
• Muscles move bone • Tendons go from muscle to bone • Evolution: muscle to tendon – M.interosseus / suspensory ligament • Ligaments go from bone to bone • Ligaments stop bone from moving – they are passive elastic – but not contractile Check ligaments go from bone to tendon Check ligaments change the function of Deep and superficial flexor tendon In full extension, function changes from tendon to ligament
• In complete extension all these ligaments tighten and stop the joints from moving
The lower joint complex
-when horse is standing still, fetlock mildly bent cranially, not completely extended.
Sesamoid Bones
-Change the direction of tendons
Navicular bone:
- in extension deep flexor tendon pushes Navicular bone into the coffin joint space
- Blocks joint and prevents hyperextension
Naviculardiseaseismainlya biomechanical Problem
• No healing if pressure is not taken off
Stabilisation of Carpal Joint
- In the standing horse, the Carpal joint is slightly flexed
- weight bearing position in the moving horse, the Carpal joint is extended.
- Multiple bones in carpal joint
- slight rotation locks carpals- moves little bones into place
- no lateral movement possible
- only flexion and extension possible
weight bearing:
Joint wants to extend
Accessory carpal bone stops carpal Joint from extending:
- Pushes forward counteracts
- sits laterally
- on medial side are flexor tendons
- check ligaments attach proximal and distal to carpals and counteract extension.
Function of Check Ligaments
When not completely weight bearing, flexor musc. works
When weight bearing: Extension in fetlock
Pulls DDFT und SDFT tight
Everything is stretched Tendons with check ligaments
function as ligaments Muscle is loose
Muscle is not working when fully weight bearing
Stabilisation of Elbow and GH joint
• Elbow Joint
Hinge Joint
Anconeal process and deep fovea prevent lateral movement
Only flexion extension possible
• Shoulder Joint
Ball and socket Joint
Scapula attached to body, so very little Rotation, adduction and abduction
Main movement is flexion extension
Main goal of stabilization is to stop flexion and extension
Stabilisation of GH Joint
Standing position
Weight pushes down on scapula
Leads to flexion of glenohumoral joint
Stabilization :
• Biceps tendon
• Big fibro cartilaginous part (very white)
• Doesn’t use much energy
• Tendons of Lacertus fibrosus and ext. carpi radialis
Stabilisation of Elbow
Standing Position
Weight pushes down on scapula
Leads to flexion of elbow
• Goal of Stabilization is to stop flexion: • Long head of triceps muscle • Olecranon - Scapula • Crosses two joints • Counteracts flexion of elbow joint • Triceps has to contract to lock stay apparatus • Uses energy!!
Attachment of Limb to Body
Main components:
Serratus ventralis muscle and pectoralis muscle
• Serratus: Individual muscle bellies, lots of inelastic fibrous tissue
Body weight is hanging of the upper end of scapula like
in a sling
Supports body, when muscles are relaxed
In Movement:
Some of the energy of concussion pulls the body up during movement
Lordosis lifts up
Serratus
C4 and lower neck are lifted up
Uses energy to “cock the bow” in engagement
Muscle contracts to prevent torque
Stay Apparatus of the Front Leg
- When stay apparatus is locked, front leg acts like a solid stick
- Energy is created from the back
- Horse„polevolts“overfrontleg
- Energy shoots up the leg
- If a joint is not stabilized and locked, energy will blow out the side
- Tissue damage /pathology can occur
- Fox example: unlocked Carpals can lead to suspensory problems
• In a standing Horse muscles except for the triceps should not work
• Soft muscles on a standing horse are positive
• In a moving horse muscles ripple when foot comes down
Soft muscles ripple when energy moves through them
Energy is neither created nor destroyed
It has to move somewhere
Dysfunction of Stay Apparatus
• If leg does not lock • Muscles are tight, energy can‘t dissipate – Energy is converted to heat Overheating Increased sweating
– Concussion to the trunk
Digestive problems ?
Metabolic changes? Sympathetic/Parasympathetic balance?
The stay Apparatus of Hind Leg
Teh goals of stay apparatus in hind led is:
-Standing still: Ability to stand with only a minimum muscular effort.
In movement:
-Ability to lift off smoothly
The stabilisation of the structures below the Tarsus is the same as in the front leg
Main structures that need stabilization are:
- Coxofemoral joint
- Stifle joint
The Coxofemoral Joint
- Ball and socket joint
- Primary weight bearing joint
- Pelvis sits on leg like a table
- When everything is balanced, very little energy needed to stabilize coxofemoral joint
- Maintained in extension by action of the hamstrings and gluteal muscles
Stifle
• Angle between Femur and Tibia Gravity leads to flexion
• Heavy ligamentous structures in the front to prevent flexion
• Stabilization of stifle in the standing and weight bearing horse:
Locking mechanism of the patella
• Stabilization of stifle in movement
Reciprocal mechanism
What are the Chiropractic Considerations in relation to the Stay Apparatus?
Muscle coordination is the most important factor for the proper functioning of the stay apparatus
Muscles are coordinated by the nervous system
Adjustment of the spine and the extremity joints can facilitate the proper function of the stay apparatus
