Knee Part 3 Flashcards
Knee Plicae
Synovial pleats, appear as folds in the synovial membranes
3 most commonly described plicae:
Inferior plica
Superior or Suprapatellar plica
Medial plica
Irritation or trauma to the knee can cause
thickened plicae which can cause pain – sometimes mimics a meniscal tear
Knee ligaments help control
- Excessive knee extension
- Varus and valgus stresses at the knee
- Ant. or post. displacement of the tibia
- Med. or lat. rotation of the tibia
- Combinations of the above
MCL Proximal Attachment
Medial epicondyle of femur below adductor tubercle
MCL Attachments
Posterior/medial joint capsule, medial meniscus, and semimembranosus tendon
MCL Distal Attachment
Medial surface of the medial condyle of the tibia deep to pes anserinus
MCL Functions
Provide medial stability against valgus stress and external rotation
LCL Proximal Attachment
Lateral epicondyle of femur
LCL Distal Attachment
Head of fibula
Blends with biceps femoris tendon
LCL passes superficial to
popliteus tendon origin
LCL Function
provide lateral stability against varus forces
Cruciate ligaments have relatively poor
blood supply
Cruciate ligaments
Resist extremes of all knee motions, most importantly
A/P shear forces
Cruciate ligaments contain
mechanoreceptors that provide proprioception
ACL Proximal Attachment
Medial surface of lateral femoral condyle
ACL Distal Attachment
Anterior aspect of the intercondylar eminence of the tibia
ACL Function
Limits the anterior displacement of the tibia relative to the femur in all positions of joint movement and limits excessive rotation
ACL Bundles primary restraint to
ant. translation (shear) of tibia on femur
PLB most taut as
knee extends
ACL Bundles in knee flexion
PLB loosens and AMB tightens
ACL Bundles resists _____
Restraint to _______
hyperextension
Varus/valgus
ACL Bundle has limited control of
med. rotation of tibia via AMB
Factors associated with noncontact ACL injury
Strong quadriceps activation over a moderately flexed or nearly extended knee
Marked valgus collapse
Excessive knee ER with femur IR at the hip relative to a fixed tibia
ACL Mechanism of Injury Common
15-25 y/o during high-velocity sports
Last 50 – 60 of knee extension: quads pull tibia anteriorly as tension in the ACL increases to limit
anterior slide of tibia
ACL Provides 85% of passive resistance to
anterior slide of tibia
Diagnosis of ACL laxity: anterior translation of tibia is greater than
8 mm than opposite knee (anterior drawer test)
Rehabilitation after ACL injury/surgery: perform
strengthening exercises for quads in knee flexion (avoid last 50 - 60 of knee extension)
PCL Proximal Attachment
Lateral side of the medial femoral condyle
PCL Distal Attachment
Posterior intercondylar area of the tibia
PCL Function
Limits posterior displacement of the tibia relative to the femur in all positions of joint movement
Less tension on PCL Between
full extension and approximately 30º- 40º of flexion
Tension peaks on PCL at
90-120 deg of flexion
Some fibers of the PCL remain taught throughout most of
flexion and extension of the knee
During squatting the PCL helps limit
anterior translation of the femur
- Clinical Applications: PCL Injury
- Look for posterior sag of the proximal tibia relative to the femur in the
supine hook lying position
Clinical testing for PCL injury:
posterior drawer test
Hamstrings are PCL ”antagonists”: PCL will limit posterior translation of the tibia when the hamstrings are
flexing the knee
Popliteus tendon helps restrain ___________ if PCL is torn
anterior translation of femur
Clinical Applications: PCL Mechanism of Injury
High-energy trauma such as MVA or contact sports (i.e., football)
Falling onto a fully flexed knee with ankle PF, e.g., the proximal tibia first strikes the ground or dashboard injury
Rapid descent into a deep squat
