This document presents two case studies of patellofemoral instability. Case one involves a 40-year-old female with a history of patellar dislocation and recurrent instability. Physical exam reveals positive tests for instability. Radiographs show a crossing sign and Insall-Salvati index of 1.15. Case two is a 33-year-old female with a history of patellar instability and failed non-operative treatment. Radiographs show femoral anteversion of 24 degrees and increased TT-TG distances. The document discusses anatomy, biomechanics, symptoms, exam findings, imaging, and surgical and non-surgical treatment options for patellofemoral instability.

1. Patello femoral instability
Case presentation
Dr. Moahammadreza Piri
Orthopaedic surgeon, Isfahan university of medical
sciences, Iran
1

2. Case number 1
History:
40 year-old female
History of falling down and left
patellar dislocation ten years ago with
recurrent dislocation of patella
Complaining of knee pain and patellar
instability
Arthroscopic surgery ten years ago
2

3. Physical exam
 Positive J sign
 Positive glide test
 Positive grind test
 Positive apprehension test
 Positive patellar tilt
 Q angle:27
 Positive active tracking
test
3

4. AP view
4

5. 5
Lateral view
Crossing
sign
Insall-Salvati index:1.15
Right Left

6. Merchant view
6

7. 7

8. CT Scan
8
TT-TG:15 mm
Shallow
trochlea

9. Case number two
history:
 33 year-old female with past history of falling down and
patellar instability
 Many unsuccessful periods of non operative treatment
including rehabilitation
9

10. radiography
 Femoral anteversion:24
 RT TT-TG:35.6
 LT TT-TG:33.6
 RT sulcus angle:166
 LT sulcus angle:175
10

11. 11

12. 12

13. 13

14. Anatomy and biomechanics
Extensor mechanism:
Vastus lat.: 7-10degree
Vastus med longus: 15-18degree
Vastus med obligus: 55 degree
 VMO is the main dynamic stabilizer
of patella
14

15. Primary stabilizers (static
factors)
1-shape of patella
2-femoral sulcus
3-normally tensioned m.capsule
4-appropriate length of patellar
tendon
15

16. 16

17. Q Angle
17

18. Q Angle
 normal range:M:8-10, F:10-15
 DDx:
1-genu valgus
2-increased femoral anteversion
3-ext. tibial torsion
4-laterally position of tibia tubercle
5-tight lat. retinaculum
18

19. Symptoms
1-pain
2-istability
3-locking
19

20. Physical examination
• Palpation
• P. glide test(20° flexion and extension)
• P. tilt test (extension)
• Apprehension test
• J sign
• Active tracking
• Hyperlaxity
• Thigh-foot angel
• Observation for malalignment
• Thigh circumference 20

21. 21

22. 22

23. Radiography
 Antroposterior
 Lateral
 Axial
23

24. 24

25. 25

26. Patella alta
 Blumensaate line
 Insall ratio  1.2
 Blackburne 1.06
 caton-Deschamps  1.3
26

27. 27

28. 28

29. Sulcus angle
29

30. CT scan
 Patellar tilt
 Femoral anteversion
 External tibia torsion
 TT-TG distance
30

31. 31

32. 32

33. 33

34. MRI
 Chronic and recurrent DX
 1st DX in athletes
34

35. 35

36. Conservative treatment
Acute patella Dx or Sx
• Knee immobilizer + jones type dressing + Ice +
crutch
• Quadriceps setting excersises
• Rehabilitation(closed-chain exccersise)
• Patellar stabilizing brace for 6-8weeks
36

37. 37
Conservative treatment
PF malaligment and recurrent patellar Sx
 Rehabilitation(quadriceps)
 Patella stabilizer brace

38. Surgical treatment
38
Acute patella Dx
• Osteochondral fx
• Joint incongruity
• Competittive athletes

39. 39
PF instability
The key to successful surgical interaction is
correctly identifying and treating the pathologic
anatomy producing the instability
Factors in patella instability:
• Trochlear dysplasia
• Patella tilt
• Patella alta
• Excessive TT-TG distance
Surgical treatment

40. 40

41. 41

42. 42

43. Lateral release
43
Isolated: parapatellar pain secondary to exccesive
lateral pressure syndrome:
1. negative patella tilt
2. <1 quadrant passive medial patellar glide
In combination: in combination with realignment
procedure when tight lat structures prevent patella
centering

44. Proximal soft-tissue procedures
• Insatability secondary to medial laxity
• Fine –tuning at distal realignment procedure
• Skeletaly immature patients
• Acute MPFL tear: MPFL repair
 Mild to moderate chronic medial laxity:
imbrication
 Moderate to severe chronic medial laxity: MPFL
reconstruction
44

45. 45

46. 46

47. Distal realignment
 Malaligment
 Q angle  20
 TT-TG  15
 Chondromalacia in lat and inf of patella
47

48. Elmslie-trillat procedure
transfer TT to medial
 Insall index  1.2
 Grade 2 or less chondromalacia
48

49. Oblique osteotomy at the
tuberosity(Fulkerson)
 Transfer TT to ant and med
 Chondromalacia grade 3 or 4
49

50. Derotational HTO
50
 Skeletaly mature
 Thigh -foot angle  30
 Tubercle sulcus angle  10

51. Trochleoplasty
51

52.  Proposed treatment for case number one:
MPFL reconstruction by STT + lateral release
 Proposed treatment for case number two:
MPFL reconstruction by STT + lateral release + antromedialization of
tibial tuberosity
52