Patellar Instability

Question 1

What way does dislocation always occur in patellar instability?

Answer 1

Laterally

Question 2

What ligament tears when patella dislocates?

Answer 2

Medial patellofemoral ligament tears

Question 3

Predisposing factors to patellar instability?

Answer 3

• Ligamentous laxity
• Female
• Shallow trochlear groove
• genu valgum
• Femoral neck anteversion
• High riding patella (patella alta)

Question 4

Investigation for patellar instability?

Answer 4

X-ray

Question 5

What would be seen on patellar instability x-ray?

Answer 5

• Small opacification: osteochondral fracture: medial facet of patella strikes lateral femoral condyle
• Lipohaemarthrosis can be seen

Question 6

Treatment of patellar instability?

Answer 6

• Physiotherapy to strengthen quadriceps
• If recurrent dislocation is frequent:
• Tibial tubercle transfer
• Medial patellofemoral ligament (MPFL) reconstruction: tendon autograft