knee kinematics & kinetics

1. KNEE JT- PATHOMECHANICS.

2. • Dissimilar surfaces
• Little/No inherent bony stability
• May be cause of additional instability if fractured
• Peroneal nerve
• More commonly injured
• Tethered around the fibular neck
• Mechanism of injury
• Tension (Varus ± hyperextension, Translation (Anterior
/Posterior dislocation)
• Direct impact
• Iatrogenic (aggressive varus/hyperextension
• Tibial nerve

3. • Direct/indirect inj-due ti sports such as
jogging,skating,skiing,football,tennis.
• Structures involved-menisci,lig,bones,musculo-
tendinous structures.
• Blow to lateral aspect of knee jt –valgus stress-
tearing of lig restraining val stress.
• Forced hyper extension of knee- tear of post lig.
• Low level force-disrupt lig weakened by
aging,disease,immobilization,steroids or vascular
insufficiency.
• Cyclic loading may also affect visco elasticity and
stifness.

4. • Isolated – only one element injured
• Combined knee injury – two elements injured
(e.g. ACL + MCL)
• Complex trauma of the knee joint– three or
more elements injured
KNEE INJURIES

5. • The medial meniscus is more movable
than the lateral. It could be injured
during the internal rotation of the lower
leg accompaigned by knee flexion.
• Axial rotation in flexed knee occurs
with med meniscus as pivot point.
• The more rididly attached medial
meniscus may tear under sudden load.
• The lateral meniscus could be injured
during the external rotation of the
lower leg accompaigned by knee
flexion
KNEE INJURY MECHANISMS

6. KNEE INJURY MECHANISMS

7. KNEE INJURY MECHANISMS

8. ACL (anterior cruciate ligemant) TEAR

9. Knee Joint Injuries
ACL rupture - most commonly damaged ligament of the
knee. Many sports apply external and internal forces to
knee.
Often caused by some type of cutting, twisting or
hyperextension.
Unlike the MCL & PCL, the ACL does not have the capacity
to heal.
Once injured, it does not reconstitute as a functional entity.

10. ACL Tear

11. Knee Joint Injuries
ACL injury rates are 4 to 8 times higher in
female athletes who take part in soccer,
basketball, track, and softball (compared to
baseball) than male athletes.
Sagittal plane landing mechanics may play less
of a role in gender-related ACL injury than
frontal and transverse plane mechanics. Effect of
fatigue on knee valgus and internal rotation may
have more consequence on female than male.

12. SYMPTOMS
• Pain
• Loss of function
• Swelling, bruising
• Muscle atrophy
• Difficulty bearing weight

13. Knee Joint Injuries
Meniscus tearing – frequently caused by
planting foot during weight bearing while body
undergoes rotation. Symptoms include pain,
accompanied by locking or buckling of the joint.
Collateral ligament sprain - one of the most
frequent knee injuries. Usually caused by
blow to lateral knee. Deep fibers of medial
collateral ligament attach to medial meniscus,
so could disrupt meniscus too.

16. Knee Joint Injuries
Chondromalacia - affects the articulating
cartilage on the interior surface of the patella.
Possibly caused by incongruence between
patella and femur. Symptoms include pain,
swelling and a grating sensation.
Osgood Schlatter Disease - usually affects
children and is caused by repeated usage of the
knee extensors. This overuse results in a tearing
or avulsion at the epiphysis of the tibial tuberosity.
Symptoms include pain, swelling, hemorrhage.

18. Knee Dislocation–
Multiligamentous Injury
• Disruption of normal
relationship of
tibiofemoral joint
• Usually requires the
injury to 2 of the 4
major groups of
ligaments

19. Classification – Injured
Structures
Schenck RC et al. 1992
V
C
N
III L ACL / PCL / LCL+PLC MCL intact
IV ACL / PCL / MCL / LCL+PLC
III M ACL / PCL / MCL LCL+PLC intact
Schenck 1992
II
arterial injury
nerve injury
fracture dislocation
Anatomic Classification of Knee Dislocations
I single cruciate + collateral
ACL + collateral
PCL + collateral
ACL / PCL collaterals intact

20. • Prolonged compressive and tensile forces-
bursitis-prepatelar bursitis-housemaid’s knee.
• Patellar plica-symptoms-pain with prolonged
sitting, stair climbing and during resisted exs
and snaping sensation.
• During flexion-plica pressed under patella-
inflammed.

21. Pathomechanics
• May occur not only with high energy but also
with low energy
• Low energy
• Athletic activity (more with contact sports)
• Fall down stairs
• Jump of the low height
• High energy
• Motor veh accidents
• Fall from height

22. Pathomechanics
• Progressive Hyperextension model
Anterior dislocation
• At around 30 degrees: tear of
posterior CAPSULE happens
• Followed by tear of PCL & ACL
DISLOCATION
• Around 50 degrees: rupture of
POPLITEALARTERY noted

23. Pathomechanics
• Cadaveric study
• Combined cruciate ligaments injury
in hyperextension
• Low rate of strain-(100%/sec)
midsubstance tear of PCL
• High rate of strain (400%/sec)
avulsion of PCL from femur
• ACL: Mixed pattern of injury