Knee Flashcards
Do all of the menisci have a blood supply?
What is the consequence of this for healing of tears?
The meniscus only has a blood supply to the outer third, so only tears in the outer third will heal. There is no point in repairing the inner 2/3 with stitches as it will not heal.
How do the MCL and LCL ligaments differ in shape?
The medical collateral ligament is broad and flat with a rich blood supply and readily heals.
The LCL is like a thin and rope and has a poor blood supply.
What is the role of the menisci?
How does the shape of the medial vs lateral menisci differ?
What is another important difference between the two?
Why is the medial compartment under a greater amount of sheer stress?
Menisci distribute load from convex femoral condyles to relatively flat tibial articular surfaces
Medial plateau slightly more concave
Medial meniscus is fixed whilst lateral meniscus is more mobile – this means that the medial is more prone to tear
Due to shape and soft tissues, knee pivots on medial compartment through flexion and extension – tibia internally rotates on flexion and externally rotates on extension
What is the function of MCL? LCL? ACL? (Two) PCL? (Two)
MCL resists valgus stress
LCL resists varus stress
ACL resists anterior subluxation of the tibia and internal rotation of the tibia in extension
PCL resists posterior subluxation of the tibia i.e. anterior subluxation of the femur and hyperextension of the knee
Which ligaments resist external rotation of the tibia in flexion?
The posterolateral corner – the PCL and LCL with popliteus and other smaller ligaments
What type of instability may rupture of the following lead to? MCL ACL PCL Posterolateral corner Multiligament injury
MCL - valgus instability
ACL - rotatory instability
PCL - recurrent hyperextension + instability decending stairs
Posterolateral corner - varus and rotatory instability
Multiligament injury can lead to gross instability
What are the four main types of meniscal tear?
Longitudinal
Bucket handle
Radial
Parrot beak
Which type of meniscal tear would you expect to heal and why?
Longitudinal - occurs in the outer third, where there is good blood supply
What functional problem do bucket handle tears cause?
What long term problem may this cause?
Locked leg
Risk of permanent flexural deformity if left for >6 weeks
What are the the main causes of meniscal injury?
What other ligamnet injury are meniscal tears associated with?
Sporting injury
Getting up from squatting position
Spontaneous degenerate tears
50% of ACL ruptures have meniscal tear
How are soft tissue injuries of the knee investigated?
MRI
What causes pain in meniscal tear?
When you tear the meniscus, shock absorbance puts more pressure on the bone heads, which have a rich nerve supply; meniscus itself doesn’t have any nerve innervation.
When should you consider arthroscopic menisectomy?
Mechanical symptoms (painful catching or locking) or irreparable tears or failed meniscal repair.
Treatment for bucket handle tear of meniscus?
Urgent surgery
How are ligament injuries graded?
Grade 1 – sprain – tear some fibres but macroscopic structure intact
Grade 2 – partial tear - some fascicles disrupted
Grade 3 – complete tear
What is the most common knee injury?
MCL tear
MCL tear
Good or bad healing prospects?
What symptoms do patients have?
Healing is expected in the majority of partial and complete tears and little or no instability.
Patients may have laxity and pain on valgus stress with tenderness over the origin or insertion of the MCL.
MCl tear
How are acute tears treated?
How long does it take for pain to settle?
How can chronic MCL instability be treated?
Acute tears are usually treated in a hinged knee brace.
MCL usually heals well, even if there is a complete tear, unless there is ACL or PCL rupture.
Pain can take several months to settle.
Chronic MCL instability can be treated with MCL tightening (advancement) or reconstruction with tendon graft.
Which ligament is the main stabilizer against internal rotation of the tibia?
What is rupture of this ligament caused by?
ACL
Rupture is usually caused by sporting injury e.g. rugby, football, skiing.
What is the rule of thirds in ACL rupture?
1/3 compensate and are able to function well
1/3 can avoid instability by avoiding certain activities
1/3 do not compensate and have frequent instability or can’t get back to high impact sport
Management of ACL rupture Is surgery always required? What can you do to the muscles to help? Success of ACL repair? Where can autograft come from
ACL rupture doesn’t mean you definitely need surgery – older patients are more likely to compensate or avoid high impact sports
Strengthening the muscles can help – i.e. compensation for deficient ligaments; ACL can also tick to PCL to give some stability
ACL repair doesn’t work - reconstruction only
Patellar tendon or hamstrings
When is ACL surgery indicated?
What is another benefit of ACL surgery?
What does it do for pain and long term risk of OA?
Rotatory instability not responding to physio
Protect meniscal damage – if you don’t do surgery then you might get a consequent bucket handle tear due to instability
Does not treat pain
Does not prevent arthritis
LCL injury Common or not? Cause by? Healing prospects? Consequence of this? Which other structure can be affected? What does it often occur in combination with?
This is relatively uncommon
It is caused by excessive varus and hyperextension
LCL doesn’t heal and can cause varus and rotatory instability
Posterior structures are stretched, including the common perineal nerve, which can result in common peroneal nerve palsy ->foot drop
Often occurs in combination with PCL or ACL injury
Management of complete LCL rupture?
Complete rupture needs urgent repair; if you get in early enough then you can repair it; if later then you have to do reconstruction with hamstring or another tendon
