Tendons

Question 1

Compare and contrast tendons and ligament
(4 mark)

Answer 1

Tendon - Muscle to bone

Ligament - Bone to Bone

Tendon - used for transfer of energy from muscle to insertion point (store elastic energy)

Ligament - to provide support to joints preventing excessive movement

Question 2

Difference between elastic and positional tendons
(5 mark)

Answer 2

Elastic tendons used during locomotion for elastic recoil and energy transfer.

Positional tendons are stiffer and less elastic to maintain static posture and limb position.

Both used to absorb landing shock but elastic take much more shock than positional tendons do.

Elastic tendons usually on flexor muscles, such as DDF, SDF, TIOM.

Positional are on extensor surfaces

Question 3

What is a bursae?
(4 marks)

Answer 3

Tough connective tissue sacs.

Contain synovial fluid.

Placed under areas of pressure.

Mainly under tendons near their insertion.

Question 4

Where are tendon sheaths found and how is it nourished?
(3 marks)

Answer 4

These are present where tendons cross joints.

Synovial fluid is secreted to lubricate the tendons over joints.

Blood supply in sheathed tendons is carried by the mesotenon where the sheath folds inwards

Question 5

What are the two types of tendon insertions and describe how they insert

Answer 5

Tendons/ligaments do not stop at the periosteum, but are attached to the periosteum to allow for appositional (increase in diameter) bone growth. Sharpey’s fibres (type I collagen) carry force into the bone.

Indirect (fibrous) -
They have a low angle of insertion. Type 1 collagen fibers which run from tendon straight into bone.

Direct (fibrocartilaginous)
High angle of insertion.
Gradation from tendon to fibrocartilage to mineralized fibrocartilage to bone:
Gradual increase in stiffness to avoid stress concentration at tendon-bone interface
Zone 1 (tendon or ligament proper)
Zone 2 (fibrocartilage)
Zone 3 (mineralized fibrocartilage)
Zone 4 (bone)

Question 6

Why does hysteresis damage tenocytes?

Answer 6

Because hysteresis generates heat which kills the tenocytes.

Question 7

What are tendon/ligament molecular components?
(3 marks)

Answer 7

Water
65% wet weight.

Collagen
30% wet weight.

Non-collagenous proteoglycans
5% wet weight.

(Tendon are elastic and able to stretch due to water content and collagen molecules)

Question 8

What are the 4 types of collagen?

Answer 8

Type 1 - Bone

Type 2 - Cartilage/tendon insertion

Type 3 - Endotenon (connective tissue which surrounds the primary, secondary and tertiary fiber bundles)

Type 4 - Basement membrane

Question 9

Describe how the structure of tendons and ligaments relates to their biomechanical properties

Answer 9

Tendons - Concept of tendons as “passive springs”.

Play an important part in locomotion.

Elastic band springs back with no input of energy.

Flexor tendons in distal limb on weight-bearing store energy when stretched. Release of elastic energy lifts foot without further energetic input.

Ligaments -

Some have high elastin content – can be strained to 30%.

Extreme is the nuchal ligament with 70% elastin allowing high strains.

Usual strain is 5-7%, fail at about 12-15%.

Otherwise similar to tendons.

Question 10

What are the three stages of tendon healing

Answer 10

Inflammation

Proliferation

Remodeling

Question 11

Critically compare intrinsic and extrinsic tendon healing

Answer 11

Extrinsic -
Fibroblasts and inflammatory cells move from external tissue sources to invade healing site and initiate, they later promote repair and regeneration. This process includes the initial formation of adhesions and requires a well-established vascular network

Intrinsic -
Cells from the endotendon and epitendon migrate and proliferate into the injury site. They establish an extracellular matrix and an internal neovascular network
Begins after the extrinsic healing and responsible for reorganization of collagen fibers and maintenance of fibrillary continuity

Movement in rehabilitation improves this fluid flow thereby improving healing and preventing scaring when laying down new collagen fibres.
Early gentle cyclic loading achieves this = walking.

Question 12

If a tendon is re-injured, where is the new injury most likely to be and why?

Answer 12

At the boundary of the healthy and scarred tendon.

Stress concentration at the healthy-scar boundary

Question 13

Why do tendons in sheaths heal more slowly than unsheathed regions?

Answer 13

Blood supply to the tendon in a sheath is more restricted due to the presence of the sheath

Question 14

What part of the healing process can lead to reduced tendon function?

Answer 14

Proliferation when there is disorganized collagen.

Question 15

Which forelimb tendons are most likely to be injured in sport horses and race horses and why?

Answer 15

Superficial digital flexors - Crosses only one functional ginglymus/hinge joint

TIOM -

Thus MCPh extension stresses the SDFT more than the DDFT, since the DIP flexes as the MCPh extends which relieves some tension on the DDFT.

Question 16

Describe the role of the Golgi tendon organ.

Answer 16

GTO detects speed and stretch in tendon.

GTO protects against stretching too fast to prevent injury.

Question 17

Give one function of the sesamoid bone

Answer 17

Protect the tendon by decreasing stress placed upon tendon

Allow movement around a corner or point of leverage

Sesamoid bones give a better mechanical advantage for moving loads.

Question 18

What is a retinaculum?

Answer 18

A retinaculum is a band of thickened deep fascia that surrounds tendons, holding them in place. It’s not part of any muscle but primarily serves to stabilize tendons.

An example being the retinaculum holding the SDFT in place whilst it runs down the hindlimb and attaches to the calcaneus.