Knee: Patellofemoral Joint

Question 1

What is the clinical significance of Hoffa’s fat pad being highly vascularized and neural?

Answer 1

Can be a source of pain. Can bleed and swell.

Question 2

How does the quad tendon compare to the patellar in terms of thickness and strength?

Answer 2

Quad tendon is thicker and stronger (now used for ACL grafts often)

Question 3

What is the ratio of Insall and Salvati?

Answer 3

Tendon Length/ Patella Height
TL/PH

Question 4

What is a normal Ratio of Insall and Salvati?

Answer 4

0.8/1.2

Question 5

If a pt’s Ratio of Insall and Salvati is >1.2, what would that tell you about their patella? What is the clinical sig?

Answer 5

Patella alta (high riding patella)

Clinical sig: unstable patella, those who tend to dislocate their patella have an alta patella

Question 6

If a pt’s Ration of Insall and Salvati is <0.8, what would that tell you about their patella? What is the clinical sig?

Answer 6

Patella infera/baja (low riding patella)

Clinical sig: increase incidence of patellofemoral OA

Question 7

Why is the MPFL important for the patellofemoral joint?

Answer 7

Stability!

Question 8

Is it more common for a patella to dislocate laterally or medially?

Answer 8

Laterally

Question 9

What 2 passive structures apply laterally directed forces to the patella?

Answer 9

1. IT band
2. Lateral patellar retinacular fibers

Question 10

What 3 passive structures apply medially directed forces to the patella?

Answer 10

1. Medial patellar retinacular fibers
2. Medial patellofemoral lig (MPFL)
3. Lateral wall of trochlear groove (prevents patella from tracking and ending up on lateral side)

Question 11

What are the 2 main active structures acting on the patella? Hint: 1 of them is a group of muscles.

Answer 11

1. Quadriceps
2. TFL

Question 12

What aspects of the patella articulate with the femur at:

135 deg
90
45
20
Terminal ext

Answer 12

135 deg: odd facets
90: superior
45: middle
20: inferior
Terminal ext: minimal contact

Question 13

T or F: The patella only shifts and tilts medially when the knee is flexed 0-30 deg

Answer 13

True.

In full ext: patella usu slightly laterally shifted and tilted

Flex >30 : shifts & tilts laterally

Question 14

About how much total movement does the patella shift and tilt?

Answer 14

~ 5 mm total shift
~ 5 degree total tilt

Question 15

Does HIGH patellofemoral jt reaction force with a SMALL contact area put high OR low stress on the jt?

Answer 15

High stress

Question 16

What is patellofemoral joint reaction force (PFJRF)?

Answer 16

• Resultant compression force acting on the PFJ
• Dependent on knee angle and mm tension in quads
  -Impacts the joint stress on PFJ

Question 17

What puts the HIGHEST stress on the patellofemoral joint? And should therefore be avoided for pts w/ PFJP.

Answer 17

Open chain loaded knee extension

NOT: squats. Pts w/ generalized PFP: don’t tell them not to squat.