Tendons and ligaments Flashcards
Describe tendons
transmit force from muscle to bone
Describe ligaments
span a joint and attach bone to bone. They passively stabilise the joint
and then guide it in its normal range of movement during loading
What are known as entheses?
osteotendinous and osteoligamentous junctions
What are tendons composed of?
Tenocytes
Water
Collagen
Type I > II
Proteoglycans
Decorin – forms cross links between fibrils
Aggrecan – areas of tendon compression
Other components
COMP
Elastin
Fibronectin
What is the hierarchy arrangement of the fibrils?
Microfibril > fibril > fibre > primary bundle > secondary bundle > tertiary bundle > tendon
What do microfibrils consist of?
multiple triple helices of collagen
What does the stress-strain curve in tendons demonstrate?
the non-linear relationship between strain the tendon and increasing stress
Describe the different sections of the stress strain curve in tendons
Toe – this is the uncrimping of the tendon fibres
Linear – this is where the tendon starts to stretch causing it to deform in a linear fashion
Failure – where the tendon is unable to stretch any further and the cross links are broken.
Describe a weight bearing tendon
These are exposed to large weight bearing loads and have an energy storing function. e.g. DDFT and suspensory ligament in horses
Describe a positional tendon
These aid in the positioning of the limb without large amounts of weight being loaded. E.g. common digital extensor tendons
Describe paratenon-covered tendons
These are tendons that are surrounded by a thickening of the surrounding soft tissue called a peritenon. They are in areas of less friction where they tend to move in straight lines. They have a rich blood supply
Describe sheathed tendons
These are tendons held within a sheath and are in areas of high friction and where they have to bend sharply e.g. the digital flexor tendons. They are less vascular so healing is more challenging.
The same tendon can have portions that are sheathed and paratenon covered e.g. the SDFT and DDFT of the horse
What can injury in tendons be caused by?
Direct / extrinsic trauma – laceration, contusions etc
Indirect / intrinsic trauma – due to overloading of the ligament leading to excess strain
Describe indirect trauma in tendons
Indirect trauma is often preceded by some form of tendon degeneration whether that be due to age, exercise or underlying pathology (ischaemia, cysts etc)
It can range from individual fibre tears to generalised defects and, worst case scenario, full thickness rupture.
Describe a strain injury in tendons
Stretching or tearing of the musculotendinous unit
Define tendonitis
Inflammation of the tendon
Describe Paratenon-covered tendons
Due to the rich blood supply, healing is often successful in these tendons but can still take several months.
What are the three stages of paratenon-covered tendon healing?
- Wound fills with blood (haematoma) and inflammatory products.
(further damage can occur at this point due to release of proteolytic enzymes)
Capillary buds and fibroblasts enter
- Granulation tissue bridges the gap
Collagen type III formed in a haphazard manner
Fibrous bridge forms
- Granulation tissue bridges the gap
Collagen type III formed in a haphazard manner
Fibrous bridge forms
Describe sheathed tendons
Healing more limited due to lack of blood supply and severed ends retract into the sheath
Require surgery to repair and immobilisation
Allows ingrowth of connective tissue and adhesion’s to form between tendon and sheath
What are the functions of ligaments?
Stabilise the joint
Help joint glide through the normal range of movement
Prevent excessive movement of joints
Joint proprioception
Describe a peri-articular ligament
These are ligaments that are not involved with the joint surface e.g. collateral ligaments
Describe intra-articular ligaments
These are ligaments within the joint e.g. round ligament of the femoral head, cruciate ligaments etc.
The composition of ligaments is similar to tendons except ligaments tend to have:
Slightly less collagen
Slightly more water and proteoglycans
Less organised collagen fibres
Describe a sprain injury in a ligament
The most common type of ligament injury is a ‘sprain’. This should NOT be confused with a strain and this relates to the musculotendinous unit.
Injury can be graded depending on severity:
Grade 1 - Mild sprain
Grade 2 - Moderate sprain or partial tear
Grade 3 - Complete tear, often leading to subluxation of the associated joint
Define desmitis
This is a term given to the inflammation of the ligament. It is seen most commonly in the horse affecting the suspensory ligament and the check ligament of the deep digital flexor tendon.
Name common clinical conditions of tendons and ligaments in horses
Superficial digital flexor tendon injury
Suspensory ligament desmitis
Check ligament desmitis
Deep digital flexor tendon injury
Collateral ligament injury
Name common clinical conditions of tendons and ligaments in canines
Supraspinatus tendinopathy
Biceps brachii tendinopathy
Medial shoulder syndrome (rotator cuff injuries)
Cranial cruciate ligament disease
Achilles tendon damage (gastrocnemius avulsion / lacerations / rupture)
