Week 6 Task Sheet - Patello-femoral Pain and OA Knee

Question 1

What is the classification of the patellofemoral joint?

Answer 1

Biaxial, simple, synovial plane joint

Question 2

What are the functions of the patella? (5)

Answer 2

• Protection of the anterior aspect of the knee (femoral condyles) from trauma
• Enhances the leverage of the quadriceps tendon on the femur – increasing the efficiency of the muscle – the anatomic pulley
• Protection of the quadriceps tendon from the friction and compressive stress across the knee joint
• Minimises concentration stress by transmitting forces evenly to the tibia – disputes force of quadriceps
• Attachment for ligaments and muscles

Question 3

What are the articular surfaces of the patella?

Answer 3

Oval articular surface divided into medial and lateral facets by vertical ridge

• lateral facet is larger - both facets are convex
• anterior surface is convex

Facets divided by transverse ridges into upper, middle and lower areas

Question 4

What is the odd facet?

Answer 4

On the medial side of the posterior surfeit of the patella - in contact with femoral condyles at 135 degrees

Question 5

What is the position of the patella in full knee extension?

Answer 5

proximal to the trochlea of the femur - resting on the supra patella fat pad and the supra patella synovium

Question 6

Where is the knee least stable and why?

Answer 6

During full extension because of the narrow trochlear

Question 7

What position is most stable and why?

Answer 7

At 90 degrees because there is most contact between the patella and the femur

Question 8

What is the patella contact force?

Answer 8

Force dependant on the size of the external moment arm

Question 9

when is the patella contact force highest?

Answer 9

During the last 20 degrees of open chain extension because the contact area is lowest but the moment arm is longest

Question 10

Why is patella contact force high in closed chain knee flexion

Answer 10

• With increased knee flexion – there is an increased length of the external movement arm –> increased PFJ contact area –> increased PFJ contact force –> increased work of quads –> patella becomes more compressed against trochlear of the femur

Question 11

What are the MEDIAL static stabilisers of the knee?

Answer 11

Medial patellofemoral ligament, medial patellomeniscal ligament, medial patellotibial ligament
Bony geometry

Question 12

What are the LATERAL static stabilisers of the knee?

Answer 12

Lateral patellofemoral ligament, deep transverse retinaculum, lateral patellotibila ligament
Bony geometry

Question 13

What are the dynamic stabilisers of the knee?

Answer 13

IT band
Vastus Lateralis 
VMO
Quads tendon
Extensor retinaculum

Question 14

Why does reduced hamstring flexibility cause PFPS?

Answer 14

Quadriceps have to work harder to achieve full extension - causes increased compression of the patella against the trochlea = increased contact force

Question 15

Why does decreased extensibility of calf cause PFPS?

Answer 15

internal rotation of tibia and reduced dorsiflexion –> change in patella tracking and reduced ability to complete knee extension –> increased stretch on quads to contract –> increased PFJ contact forces

Question 16

Why might reduced medial glide of patella indicate PFPS?

Answer 16

Soft tissue shortening of the lateral structures (e.g. IT band) can cause malt racking and lead to pain and stiffness

Question 17

Why might a patient with OA have a tight IT band?

Answer 17

dur to holding knee in flexion - as loose pack position is less painful

Question 18

How does knee joint swelling change PFJ function?

Answer 18

Synovial fluid due to effusion fills supraatella fat pad - can cause:

• inhibition of inner range buds,
• increases distance between patella and trochlea (decreasing congruency)
• PFJ instability and pain