knee problems and knee injuries overview
TRANSCRIPT
Gross Anatomy: Bones
patellar surface
intercondylar eminence
Gross Anatomy: Skeletal Structure
22
Gross Anatomy: Articular Surfaces
Gross Anatomy: Menisci
Fibrocartilaginous structures
Attach to tibia in intercondylar region
Transverse ligament connects the
anterior horns of each menisci
Vascular periphery (2-3 mm)
Medial meniscus
Oval-shaped
Attached to MCL
Thinner , less mobile
Lateral meniscus
Circular
Thicker, more mobile
Gross Anatomy: Synovial Membrane
MM
PCL
ACL
LM
Does not invest cruciate ligaments!
Bursae:
•Suprapatellar
•Subpopliteal
•Prepatellar
•Subcutaneous
infrapatellar
•Deep infrapatellar
Gross Anatomy: Ligaments
Medial Collateral (MCL)
Lateral Collateral (LCL)
Anterior Cruciate (ACL)
Posterior Cruciate (PCL)
Meniscofemoral (MFL) Meniscofemoralligament
Gross Anatomy: Muscles Thigh
Quadriceps femoris – VL, VM, VI, RF
Sartorius
Gracilis
Hamstrings – BF, SM, ST
IT band – GM, TFL
Leg Gastrocnemius
Plantaris
Popliteus
(Pes anserinus)
Gross Anatomy: Popliteal Fossa
1. Semitendinosus
2. Biceps femoris
3. Semimembranosus
4. Sciatic nerve
5. Popliteal vein
6. Popliteal artery
Tibial n. Common peroneal n.
Gross Anatomy: Vasculature Patellar Plexus
Anastomoses of descending branch of lateral circumflex femoral a., anterior tibial recurrent a., and genicular branches
Popliteal Artery
Med./Lat. Superior Genicular
Middle Genicular – enters capsule post. to supply ligaments and synovium
Med./Lat. Inferior Genicular
Circumflex Fibular
Gross Anatomy: Nerve Supply Sciatic nerve
Tibial n.
Common peroneal n.
Wraps around head of fibula
Saphenous branches
Run deep to pes anserinus
Patellar Dislocation Predisposition
Genu valgum
Overweight
Patellar hypermobility
Weak quadriceps
Mechanisms Direct contact to
medial side
External tibial rotation with forceful quadriceps contraction
Patellar Dislocation
Vastus medialis strain
Tearing of medial patellar retinaculum
Hemarthrosis
Reduces with extension
Patellar Dislocation: Diagnosis Obvious if not yet
reduced
Patellar hypermobility/ apprehension test
X-ray/MRI only necessary to rule out osteochondral fractures, other associated injuries
Patellar Dislocation: Treatment Knee extension
Aspiration to relieve discomfort and check for fat in blood
Surgery unnecessary unless osteochondral fracture or complete rupture of MPFL
Crutches, PRICES
Rehabilitation focusing on vastus medialis
Meniscal Tears Shear force from femur
Acute or degenerative
Athletes, elderly, overweight
Vascular zone?
Horizontal Within substance
Longitudinal Bucket handle – ACL risk
Radial or vertical Parrots beak
Medial Meniscus Tear Tears easier than lateral
due to certain traits
Squatting
Internal rotation of tibia with knee flexed
Member of “unhappy triad” Medial meniscus
MCL
ACL
Medial Meniscus: Diagnosis MRI
Low-signal intensity (black triangle ) = normal
White interruption = lesion
Arthroscopy as last resort
Lateral Meniscus Tear Lower incidence
Often more painful
More likely to incur radial or parrots beak
Not rare for anterior horn
Discoid meniscus
Wrisberg variety
Congenital (1.5-3%)
MM only 0.1 – 0.3%
femur
Discoid meniscus
MCL: Diagnosis: Examination Abduction stress test
First at 30
Again at full extension Rule out PCL tear
Anterior drawer test with external rotation of tibia Hip flexed 45
Knee flexed 90
Tibia rotated 30 ext.
Anterior rotation of medial tibial condyle
MCL: Diagnosis: Imaging X-ray
Only useful for young patients to differentiate from epiphyseal fracture
Taken at 20-30 flexion Enlarged joint space = tear
MRI Coronal scan Normal MCL looks thin,
taut, low-signal Grade I: indistinct MCL
(edema) Grade II: thicker, looser Grade III: severe edema
MCL: Treatment Surgery necessary for
compound injury
Crutches + PRICES + rehab for Grade I, IIonly if isolated
Grade III tears may require surgical repair, but immobilization can be effective if isolated(rare) 3-4 months recovery
Surgery Open incision
Midsubstance ruptures sutured
Tear from bone repaired with suture anchors
Lateral Collateral Ligament Courses slightly posterior
Sprained least frequently
Adduction force rare
BF, popliteus, IT tract
Flexed knee = isolated tear
Anteromedial blow hyperextension/ postero-lateral corner injury
Risk to common peroneal nerve
Foot drop, sensation loss
LCL: Diagnosis: Examination Adduction stress test
At 30, then full extension
Ext. rotation recurvatum Lift legs by great toes Recurvatum + ext rotation +
varus = PL corner injury
Posterolateral drawer test Tibia externally rotated,
posterior force applied
Reverse pivot shift test Knee 90, tibia ext. rotated With valgus, slowly extended
Temporary posterior subluxation of lateral tibial condyle around 30
Forcibly reduces with extension
LCL: Imaging and Treatment MRI
Coronal oblique scan
Sagittal scan to rule out fibular fracture, avulsion
Tear looks less taut or discontinuous – no thickening
Treatment Similar to MCL
Grade III usually requires surgery
Anterior Cruciate Ligament Most common knee injury
among athletes AM fibers taut in flexion
Check anterior displacement
PL fibers taut in extension Check rotation
Hyperextension, internal rotation – rarely isolated injury from contact force
“unhappy triad” May tear from tibia (3-10%),
from femur (7-20%), or in midportion (70%) Proximal end receives branch
from middle genicular a.
Internal rotation of right knee
(LEFT KNEE)
ACL: Diagnosis: Examination History, large hemarthrosis Autonomic symptoms Anterior drawer test
Tibia neutral, pull ant. NOT RELIABLE BY ITSELF
Lachman test Knee only flexed 15-20
Pivot shift/jerk test Start in extension, tibia
internally rotated, valgus Slowly flex, lateral tibial
condyle temporarily subluxates anteriorly ~30
Reduces with further ext. Jerk test opposite (90o)
ACL: Diagnosis: Imaging
X-ray Segond fracture of
lateral tibial condyle
ACL tear with it 75-100%
Tibial spine avulsion in young patients
MRI – 95% accuracy All 3 planes in full
extension
Edema/hemorrhage often obscures ACL
Normal ACL Torn ACL
ACL: Treatment Extrasynovial, heals
poorly
Partial, isolated tears may be treated with PRICES, rehab, bracing of slightly flexed knee
Most tears, athletes will require reconstruction
Posterior Cruciate Ligament Broader, longer, stronger
PM and AL fiber bundles
Receives better vasc. from MGA, synovial membrane
Checks post. displacement
Tears much less frequently
Only in isolation when “dashboard knee” injury
Hyperextension in sports, especially with side force
Falling to ground with foot plantar flexed
Posterior view
Anterior view
Medial femoral condyle
PCL: Diagnosis Posterior drawer test
Neutral start vital!
Gravity or sag test
Hips at 45 or 90, compare tibialtuberosities for sag
Abduction/adduction stress test at full extension
X-ray to confirm sag test
MRI shows lower-signal intensity for intact PCL compared to ACL due to its fiber organization Take on all 3 axes, but best
is sagittal oblique
negative positive
Cruciate Ligament Reconstruction
Complete excision followed by graft insertion
Allograft
Autograft
Patellar, quadriceps, hamstrings, calcaneus tendons used
Undergoes biological modifications: inflamed, necrotic revascularization extrinsic fibroblasts repopulate
ACL Reconstruction Autografts
B-PT-B
Quadruple hamstrings Semitendinosus, gracilis
Only replace AM
Double-Bundle Provides rotational
stability
BTB as AM bundle Fixed at 20
ST as PL bundle Fixed at 90
PCL Reconstruction Usually allograft –
calcaneus tendon
Incorporates well with long-term stability
BTB and ST often too short
Can achieve full function with reconstruction of just AL bundle
A. Low-power view cross section of PCL 11 years after calcaneus tendon graft. B. High-power
A B
Future of Reconstruction Goals:
Improve recovery time
Improve remodeling of insertion sites
Improve nervous and vascular restoration
With biological manufacture of: Growth factors, cytokines
Antibiotics
Techniques: Gene therapy – viral/non-viral vector delivers specific gene
Tissue engineering – mesenchymal stem cells