Ligament injuries + meniscal tears Flashcards
What is a ligament and what does it consist of?
Span joints and anchor bone to bone can also connect some soft tissue structures.
βThey are composed of dense bundles of mainly type 1 collagen interspersed with cells called fibrocytes.
βSmall amount of ground substance.
What is the function of a ligament?
Primary function is restraining and limiting movement
What are the 4 main ligaments in the knee (and features)?
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Cord-like structure that resists varus forces particularly at 30 degrees of flexion. Also resists some axial rotation.
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Extensive (from medial femoral condyle + medial tibia) Has a superficial portion - primary stabiliser to valgus stress - and deeper portion - blends with capsule + medial meniscus as a secondary restraint to valgus force.
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Two main bundles of fibres making up the ligament (anteriomedial + posteriolateral fibres). Different parts taught in diff. posisiotns.
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Gives some rotational stability
Main function of the PCL?
preventing posterior translation of tibia relative to femur OR limits femur moving anteriorly on tibia
Main function of the ACL?
preventing anterior translation of the tibia relative to the femur.
What is the importance of the posterolateral corner?
- multiple structures in this corner interact to provide stability to the knee: PCL,LCL, popliteus tendon, popliteofibular ligament
- if damage occurs to these structures, it can cause a lot of instability
What are the most common lig. injured in knee?
ACL + MCL
Process of ligament healing?
β haemorrage + haematoma formation
β inflammation; haematoma replaced with granulation tissue (influx of inflammatory cells and macrophages)
βfibroblastic phase (fibroblasts secrete extracellular matrix and immature type 3 collagen initially)
βremodelling of the ligament (less cellular, more fibrous, more organised, type 3 col. replaced by type 1, movement organises collagen along lines of stress)
process can take months/years and the final repair (not regeneration) is likely to have altered the ligaments mechanical properties
What is a first degree ligament injury?
- most common and least severe sprian
- < one third of the ligament substance is damaged
- this degree usually results in some localised swelling + localised tenderness
- pain on stress testing the ligament but no instability as intact fibres βsplintβ damaged area
What is a second degree ligament injury?
- 1/3 to 2/3 of the ligament substance is damaged
- greater pain and disability overall
- localised swelling + often a concurrent effusion due to damage of synovial membrane
- subjective complaint of instability
- laxity + instability may present depending on the degree of damage
- heals slower than 1st degree
What is a third degree ligament injury?
- over 2/3 of the ligament substance is damaged and there can be a complete rupture
- often severe pain and very functionally disabling
- there is usually an effusion and instability + joint ROM will be markedly affected
- high likelihood of damage to other structures in and around the joint due to amount of force that has caused injury
What are the two mechanisms of MCL injury (silva et al 2015)?
Direct valgus blow to the lateral side of the knee.
Non-contact rotational injury (external rotation force) - common in pivoting sports e.g. football when boot stuck in ground
- PAIN IS USUALLY IMMEDIATE + LOCAL TO THE MCL/MEDIAL ASPECT OF THE KNEE
- effusion can develop slowly over a few hours
How is the LCL injured?
Injured with a varus force
Management of collateral ligament injury?
- MCL + LCL have good healing capacity
- Usually managed conservatively (even a third degree tear); Brace used during rehab period
- Surgery possible due to ongoing instability e.g. repair
How does an ACL injury/rupture occur?
- Pivoting athletes, those involved in contact sport
- Thought 70-80% cases of these caused by non-contact mechanism.
- Usually sudden decelerating combined with a change in direction or landing on one leg
- Combined valgus, anterior displacement + internal rotation of tibia
Indicators of an ACL injury/rupture?
β There is often significant knee pain at the time of injury (some arenβt always painful)
β Popping/immediate feeling of instability - as knee moved out then back into position
β Unable to continue sport
β Immediate swelling (within 2hrs) indicative of haemarthrosis
β 10% occur in isolation, commonly combined with/other injuries
β Patients with severe injury to the tibial plateau or tibial eminence has been avulsed show true locking of the knee.
Why does haemarthrosis occur after ACL injury?
As ACL has abundant blood supply meaning extensive haemarthrosis occurs.
Who is ACL surgery reserved for?
Patients with functional instability which has failed to improve with conservative management.
When are patients suitable for ACL reconstructive surgery?
when:
- effusion has dissolved
- gait pattern is normal - normal stance phase w/heel strike and a knee that can fully extend during gait cycle.
- full ROM
- good quads control
ACL reconstruction procedure?
β graft taken from semitendinosis but patella grafts also used
β graft will βremodelβ over 2 years following surgery
β extensive rehab period
= rehab divided into phases, lengthy process + re-injury common
What is the future risk after ACL injury?
Osteoarthritis often develops in both conservatively managed and surgically managed patients w/ACL reconstruction.
At even higher risk if also had meniscal injury.
How do PCL injuries occur?
- Caused by a blunt force to the front of the proximal tibia e.g. sporting contact, road traffic accident.
- Direct trauma to a bent knee
- Individuals may describe a popping/tearing sensation during injury + pain is often significant
Can be injured with other structures (posterolateral aspect) - complex injury leading to instability
Structure of the medial menisci?
- Semi-circular
- Covers 51%-74% of medial articular surface
- Posterior horn firmly attached to posterior intercondylar area of tibia
- Anterior horn - 7mm anterior to ACL
- Relatively immobile due to itβs firm attachment to deep surface of MCL + is continously attached to the joint capsule peripherally.
Structure of the lateral menisci?
- Greater variety in size, shape and thickeness than MM
- Broader posteriorly than anteriorly
- Almost circular in shape
- Covers larger area of tibial articular surface at 75% - 93%
- Connected to medial femoral condyle via the ligament of Humphrey + ligament of Wrisberg
- Does not have direct attachment to collateral ligs. - loose peripheral attachment to LCL
- Greater mobility than MM
