The document elaborates on the knee joint, describing its double condyloid structure with six degrees of freedom, and the roles of ligaments, menisci, and muscles in facilitating movement and stability. It details the mechanics of knee flexion and extension, including the movements of the femur and tibia along with the patellar dynamics during these actions. The document also addresses the implications of patellar position and tendon length on joint function and potential instability.

1. AKHILA NATESAN

2.  Double condyloid joint.
 6 degrees of freedom –
1. 3 rotations –
-Flex/Ext.
-Varus/Valgus.
-Int/ext rotations.
1. 3 translations.
- AP 5mm- 10mm
- Compression/ Distraction - 2-5 mm.
- Medial/Lateral 1-2 mm.

3. Menisci
FUNCTIONS –
•Increases joint
congruence.
•Distributes weight
bearing forces.
•Acts as a shock
absorber.
•Decreases friction
between joint
surfaces.

4.  Medial collateral ligament.
 Lateral collateral ligament.
 Anterior cruciate ligament.
 Posterior cruciate ligament.
 Posterior capsular ligament.
 Meniscofemoral ligament.
 Iliotibial band.

7. Primary motions :
1. Flexion / Extension – Frontal axis, saggital
plane ( 1300-1400 / 50-100)
2. Medial / Lateral rotation –Vertical axis,
transverse plane ( At 900 flexion, both 400)
Secondary motions :
1. AP displacement of femur on tibia.
2. Abduction/Adduction through valgus or
varus force.

8.  Early 0 0-25 0 knee flexion –
Posterior rolling of femoral condyles
 As flexion continues –
Posterior roll + anterior glide.

9.  Menisci during flexion –
Menisci migrates posteriorly
because of –
1. Semimembranosis
attachment to medial
meniscus.
1. Popliteus attachment
to lateral meniscus.
 So femur has to move uphill & menisci
causes anterior translation of femur.

10.  Reversal of flexion.
 Early extension –
Anterior rolling of femoral
condyle on tibial plateau.
 As extension continues –
Anterior rolling accompanied by
simultaneous posterior glide on femur.

11.  Menisci migrates anteriorly because of
meniscopatellar ligament.
 Therefore, causing posterior
translation of femur.

12.  When tibia flexed on femur –
Tibia performs both posterior rolling and
gliding on relatively fixed femoral condyles.
 When tibia is extended on a fixed femur –
Tibia performs both anterior rolling and gliding
on fixed femoral condyles.

13.  CKC FEMORAL EXTENSION FROM 300
FLEXION –
 Larger medial femoral condyle continues
rolling and gliding posteriorly when small
lateral side has stopped.
 This results in medial rotation of femur on
tibia, in last 50 of extension. (Automatic
rotation).
 OKC – Lateral rotation of tibia on femur.

14.  To initiate flexion, knee must be unlocked
 A flexion force will automatically cause lateral
rotation of femur.
 Popliteus is the primary muscle to unlock the
knee

15.  Maximum range is available at
90 knee flexion.
 Magnitude of rotation
diminishes as knee
approaches both full
extension and flexion.
 Medial condyle acts as pivot point , while
lateral condyles move through greater arc of
motion.

16.  Antero posterior axis, frontal plane.
 80 at full extension.
 130 to 200 of knee flexion.

17.  KNEE FLEXORS –
Semitendinosus, semimembranosus, biceps
femoris, sartorius, gracilis, gastrocnemius,
popliteus, plantaris.
 Except biceps femoris all are medial rotators of
tibia.
 KNEE EXTENSORS –
Quadriceps.
Patella as a movable pulley increases moment
arm by increasing distance beween quads
tendon and patellar tendon from knee joint.

18.  One of the most incongruent joints.
 Vertical position of patella in femoral sulcus is
related to length of patellar tendon – 1:1 – insall
salvati index.
 If patellar tendon longer- patella rests more
superiorly- patella alta – Larger knee ROM and
instability - more chances of subluxation.
 At fully extended knee, only inferior pole in
contact.

19.  Contact moves superiorly as flexion progresses –
 At 10 – 20 of flexion –
Inferior margin of medial lateral
facet.
 At 90 flexion –
All portion except odd facet.
 Beyond 90 flexion –
Odd facet achieves contact for
the first time.
 At 135 of flexion –
Contact on lateral and odd facet

20.  During extension – patella moves superiorly
tilts laterally and shifts laterally.
 Flexion – patella moves inferiorly , tilts and
shifts medially.

21.  At full extension posterior compressive force
by quadriceps areminimized.
 As joint angle reduces – PFJ compression
increases.
 Medial facet bears majority of compressive
force.

22.  PFJ is under permanent control of 2
restraining mechanism across each other at
right angles –
 Transverse group –
1. Medial lateral retinaculum.
2. Vatus medialis and lateralis.
 Longitudinal stabilizers –
1. Patellar tendon – inferiorly
2. Quadriceps tendon - superiorly.

23.  Kinesiology mechanics and pathomechanics;
2nd edition. Carol. A. Oatis.
 Joint Structure and function; 5th edition.
Cynthia norkins