Knee Flashcards
What kind of joint is the knee
Synovial hinge - flexion - extension
What is the normal range of movement of the knee
5-130
What ligaments strengthen the joint capsule
Lateral collateral ligament Medial collateral ligament Patellar ligament Oblique popliteal ligament Arcuate popliteal ligament
Which bursa articular with the joint cavity
Suprapatellar - largest, proximal to joint
Popliteal bursa - posterior, bakers cyst
Anserine (semimembranosus)
Gastrocnemius
What are the deep fibres of the medial collateral ligament firmly attached to
medial meniscus
What passes deep to the lateral collateral ligament
Tendon of popliteus
Difference between the anterior and posterior cruciate ligaments
Anterior - weaker, poor blood supply
- prevents posterior rolling of femur on tibia and hyperextension of knee
Posterior - stronger
- limits anterior rolling of femur on tibia and hyperextension of knee
What is the mechanical axis of the knee
Hip centre to ankle centre should pass through knee centre
What is the anatomical axis of the knee
Knee-angle (tibiofemoral angle) is 6 degrees valgus relative to mechanical axis - as the centre o the femoral shaft is 6 degrees valgus off the mechanical axis but the centre of tibia is parallel to mechanical axis
how is the knee angle in relation to the mechanical axis
3 degrees varus (3o off from being perpendicular to MA)
What are the static and dynamic soft tissue constraints of the knee
Static - collaterals, cruciates, capsule, ITB, meniscii
Dynamic - quadriceps, hamstrings (BF, ST, SM), gastrocnemius, popliteus
Extensors of knee - innervation, origin and insertion
Femoral nerve
Rectus femoris - AIIS + sup. ace. rim –> ischial tub.
Vastus med. - intertroch. line + med. linea aspera –> tib. tub.
Vastus lat. - GT + lat. linea aspera –> tib. tub.
Vastus intermedialus - prox. fem. shaft –> tib. tub.
Flexors of knee - innervation, origin and insertion
Sciatic - gastrocnemius S1
Biceps femoris - ischial tub + linea aspera –> fibula head / lat tibia
Semimembranosus - ischial tub. –> pes anserinus
Semitendinosus - ischial tub. –> medial condyle of tibia
Gastrocnemius - med & lat fem. condyles –> Os Calcis via achilles tendon
What are the meniscii and what are their function
Crescentric plates of fibrocartilage
Are avascular centrally
- load transmission
- stability
- proprioception
- shock absorption
difference between the medial and lateral meniscus
Medial
- C-shaped
- adheres to deep surface of MCL
- less mobile as firmly attached to tibia
Lateral
- circular and smaller
- more freely mobile
- popliteus tendon separates it from LCL
Mechanism of meniscal injury
Twisting movement on a loaded fixed knee
Clinical features of meniscal injury
Painful squelch Joint-line tenderness Slow swelling - quicker in young Painful weight-bearing Locked knee
How does the menisci allow slack and increased movement of the joint
The radial component of the loading force is balanced by tensile stresses developed in the circumferentially orientated collagen fibres
What are the different zones in the meniscii
Radial zone
Red / White Zone - good blood supply so heals well
White Zone - not good blood supply so doesn’t heal as well
Blood supply of the meniscus
Branches from the inferior medial and lateral geniculate arteries form the perimeniscal capillary plexus
This plexus forms the circumferential vessels and penetrating radial vessels
Repair techniques for meniscal tears
Meniscal repair
Partial meniscectomy
Meniscal transplantation
What is the typical injury triad of knees
ACL tear + medial collateral ligament + medial meniscus
Mechanism of medial collateral ligament tears
Severe medial tear due to blow to lateral knee (valgus stress)
Low grade due to non-contact valgus and external rotation injuries (i.e. skiing)
Clinical features of medial collateral ligament tears
Medial knee pain No or minimal effusion (MCL attached to capsule so fluid just leaks out into tissues causing bruising) Bruising to one side (ecchymosis) Laxity to valgus stress May hear or feel pop if severe
Mechanism of injury in ACL tear
Posterior blow to tibia
OR
Rotation injury with foot fixed to ground (knee buckles during pivot)
Clinical features of ACL tear
Pop
Quick swelling (haemarthrosis)
Inability to return to activity
+ve anterior draw sign
What may you see on an x-ray of ACL tear
Haemarthrosis
Segond fracture
Treatment of ACL tear
Full ACL rehab - rest and physio ACL reconstruction (if athlete or increased knee instability)
What other injury is common with ACL tears
Avulsion fractures of the tibial intercondylar region
What is osteochondritis dissecans
An osteochondral fragment separates from underlying bone, typically from the lateral side of the medial femoral condyle
Symptoms of osteochondritis dissecans
Pain after exercise
Intermittent knee swelling
Locking - may occur
Treatment of osteochondritis dissecans
Reattachment of fragment (if seen acutely)
Removal of loose bodies
Microfracture chondroplasty
Artificial cartilage implantation
Investigations for patient with knee pain
MRI - clinical confirmation but do x-ray first
X-ray - check for #, loose bodies, ligament avulsion, osteochondral defect, DJD
USS - tendon rupture, meniscal tear, swelling, cyst
What history do you want to know from a patient with knee pain
Environment - sport, work Activity - sports tackle, jumping Energy - how fast / heavy Systemic symptoms Chronology - is it quick or slow onset, previous injury? Hear or feel pop Swelling - early or late
