This document discusses patellofemoral instability, including its anatomy, biomechanics, evaluation, and management. It begins by introducing patellofemoral instability as a common orthopedic problem. Key anatomical structures that provide stability to the patellofemoral joint are described, including the trochlear groove, medial patellofemoral ligament, and quadriceps muscle. Evaluation involves assessing factors like the Q-angle, patellar tracking and tilt, and imaging findings. Management depends on whether the instability is acute or recurrent/chronic. For recurrent patellar dislocations, various surgical procedures are discussed to address underlying anatomical abnormalities, including medial patellofemoral ligament reconstruction, tibial tubercle osteotomy

1. PTELLOFEMORAL INSTABILITY
Dr.G.Ramesh
M.S(Ortho)
Asst.Professor
Dept. of Orthopaedics
Gandhi Medical College
Secunderabad

2. PATELLO FEMORAL INSTABILITY
INTRODUCTION:
 patello femoral instability is a common but challenging treatment problem for an
orthopaedic surgeon
 The patellofemoral joint has a low degree of congruency by nature, hence it is
susceptible to dislocation
 Dislocation is a result of anatomical abnormalities and/or insufficient soft tissue
restraints
 Non-surgical approaches have been advocated to treat acute patellar
dislocation, while many operative procedures, including proximal soft tissue or
distal bony realignment procedures are designed to treat chronic / recurrent
patellar dislocations
 Addressing the specifics of anatomy, biomechanics, history, physical examination
, and radiographic interpretation can shed important light on the treatment
options of acute and recurrent patellar dislocations/and subluxations

3. PATELLO FEMORAL INSTABILITY
Anatomy
Passive stabilizers
1. trochlear groove : primary bony stabilizers:
depth, height
patellar engagement
2 medial patello femoral ligament (MPFL):
primary static soft tissue stabilizer
Dynamic stabilizer
quadriceps (VMO)

4. PATELLO FEMORAL INSTABILITY
Biomechanics
stability and normal tracking of the patella with knee flexion requires a
complex co ordination of static and dynamic stabilizers. From o° to 30° of
the knee flexion, medial patello femoral ligament and other soft tissue are
primary restraints to lateral patellofemoral dislocation. With the greater
knee flexion , the bony confines of the lateral femoral condoyle and
trochlear groove captures the patella and patellar stability

5. PATHOLOGIC ANATOMY OF PATELLAR DISLOCATION
H. dejour classification
Primary instability factors
1. Trochlear dysplasia
2. Patella alta
3. Patella tilt
4. ↑ TT-TG distance(‘q’ angle quantification by CT scan)
Secondary instability factors
1. Excessive external femoral rotation / Excessive femoral ante version
2. Excessive external tibial rotation
3. Genu valgum
4. Genu recurvatum
( these underlying pathologies predispose to an acute over load of soft tissue
stabilizers and rupture of MPFL with patellar dislocation following minimal trauma)

6. PATELLO FEMORAL INSTABILITY
Who tends to recur
• Young
• Female
• Family history
• Bilateral
• Atraumatic disorders
• Anatomic abnormalities
patella alta
trohlear hypoplasia
↑TT-TG distance
↑ ‘q’ angle
quadriceps dysfunction
hyper mobility

7. PATELLO FEMORAL INSTABILITY
Evaluation
We evaluate the following features
1. Integrity of medial patello femoral ligament
2. Height of patella on physical and radiographic examination
3. Length of patellar tendon
4. Position of patella in relationship to trochlea

8. PATELLO FEMORAL INSTABILITY
physical examination
gait
standing alignment
‘Q’ angle
J sign
laxity
rotational malalignment

9. PATELLO FEMORAL INSTABILITY
physical examination
gait
standing alignment
‘Q’ angle
J sign
laxity
rotational malalignment
for males : mean ‘Q’ angle is 10͔°
for females : mean ’Q’ angle is 15°±5°
↑’q’ angle leads to relative lateral shift of patella
↑’Q’ angle results from
↑femoral external rotation
↑external rotation
genu valgum
tibia vara

10. PATELLO FEMORAL INSTABILITY
physical examination
gait
standing alignment
‘Q’ angle
J sign
laxity
rotational malalignment
observe the movement of the patella during active knee extension,
lateral subluxation of the patella as the knee approaches full extension
is indicative of j sign positive
positive j sign indicates ↑ lateral force or ↑ ‘q’angle

11. PATELLO FEMORAL INSTABILITY
physical examination
gait
standing alignment
‘Q’ angle
J sign
laxity
rotational malalignment
patellar laxity
patellar translation is assessed by passively
moving patella medially and laterally with
knee at 0° and 30° of flexion, the amount of
translation is quantified in quadrants. Normal
glide is one but more than two quadrants indicates
laxity

12. PATELLO FEMORAL INSTABILITY
physical examination
gait
standing alignment
‘Q’ angle
J sign
laxity
rotational malalignment
patellar tilt
it is done with knee in full extension
normally patella can be tilted so that
the lateral edge is well anterior to the
medial edge
inability to do this indicates lateral
retinacular tightness

13. PATELLO FEMORAL INSTABILITY
physical examination
gait external tibial torsion
standing alignment
‘Q’ angle
J sign
laxity
rotational malalignment
 Measured by he relation ship of the transmalleolar axis to the Coronal axis of the
proximal tibia, is typically neutral
 tibial torsion also may be assessed through measurement of the thigh-foot
angle, average values are 5°internal
leads to ↑’Q’ angle and ↑ TT-TG distance

14. PATELLO FEMORAL INSTABILITY
physical examination
gait excessive femoral ante version
standing alignment
‘Q’ angle
J sign
laxity
rotational malalignmen
measured by hip rotations with the patient in prone position with hips extended and
knees at 90°of flexion
Normal range of hip rotations are about 45°. With ↑ femoral antevertion range of I.R.
increases and range of E.R. reduced
conditions leads to ↑’q’angle and
↑TT-TG distance

15. PATELLO FEMORAL INSTABILITY
Radiographic evaluation
1. long standing weight bearing hip-to-ankle, A.P view
helps in assessing the angular deformity of knee
i.e. genu varum and genu valgum

16. ..
PATELLO FEMORAL INSTABILITY
Radiographic evaluation
Lateral view with 30° of knee flexion
Insall-salvati ratio:
normal value: 1.0 to 1.2
↑value indicates: patella alta
When patella alta is present ,the patella becomes engaged with greater degrees of
knee flexion , where the patella is not captured and it is at increased risk for
instability

17. PATELLO FEMORAL INSTABILITY
Radiographic evaluation
Lateral view with 30° of knee flexion
trochlear dysplasia:
crossing sign
double contour

18. PATELLO FEMORAL INSTABILITY
Radiographic evaluation
Merchants view: tangential axial view of patello femoral joint obtained with knee in 45° of flexion
Sulcus angle
normal angle : 140°
> 140° : trochlear dysplasia
Congruence Angle
normal : -8°to+14°
>14° indicates lateral subluxation
Lateral Patello Femoral Angle
normal: angle opens laterally
abnormal : angle opens medially
or lines become parallel

19. PATELLO FEMORAL INSTABILITY
CT scan evaluation
• Helps in assessing the bony anatomy and architecture of patello femoral joint at different
angles of knee flexion
• The protocol includes mid-axial images obtained from 0°to60° of flexion in 10° of increments
• Is quantification of ‘q’ angle
TT-TG distance : normal measures are 2to 9 mm
borderline measures are 10to 19 mm
pathological > 20°
Sulcus angle
Congruence angle
Trochlear depth

20. PATELLO FEMORAL INSTABILITY
CT scan evaluation
The protocol includes mid-axial images obtained from 0°to60° of flexion in 10° of increments

21. MANAGEMENT OF PATELLO FEMORAL INSTABILITY
Types of patellar dislocations
Acute patellar dislocations
Chronic / recurrent patellar dislocations
Acute patellar dislocations
Results from high energy transfer, where anatomy of joint is normal
Results from internal rotation of femur on a fixed externally rotated tibia
Major sequelae of acute patellar dislocation is tear of medial patello
femoral ligament (MPFL)
In general most acute dislocations are treated non-operatively unless
associated with an osteochondral injury
When surgery is needed MPFL is repaired / reconstructed

22. MANAGEMENT OF RECURRENT PATELLAR INSTABILITY
 Defined as the condition where patellar dislocation had occurred at least
twice, or where patellar instability following initial dislocation had
persisted for more than three months
 A large number of procedures have been described to treat recurrent
patellar dislocations
 No single surgery is universally successful in correcting the chronic patellar
instability
 We need to customize surgery based on the knee problem
 Our approach is to identify the underlying problem that cause the patello
femoral instability and systemically correct them

23. MANAGEMENT OF RECURRENT PATELLAR INSTABILITY
The surgical procedures are classified into
Proximal Realignment Of Extensor Mechanism
1.Lateral retinacular release
2. Medial plication/ reefing
3. VMO advancement
4.MPFL reconstruction
Distal Realignment Of Extensor Mechanism
Medial or antero medial displacement of tibial tuberosity

24. MEDIAL PATELLO FEMORAL LIGAMENT RECONSTRUCTION
 The procedures like medial plication, vmo advancement, and lateral
retinacular release are non anatomic procedures
 They don’t address the principle of pathology in recurrent patellar
dislocation
 Medial patello femoral ligament (MPFL) is the primary soft tissue passive
restraint to pathologic lateral patellar dislocation, and MPFL is torn when
patella dislocates, hence reconstruction of MPFL is done in an attempt to
restore its function as a checkrein

25. MEDIAL PATELLO FEMORAL LIGAMENT RECONSTRUCTION
Anatomy of medial patellofemoral ligament
 MPFL arises from medial surface upper two thirds of patella above
equator and inserts into a groove between adductor tubercle and medial
epicondyle

26. MEDIAL PATELLO FEMORAL LIGAMENT RECONSTRUCTION
Procedure
indicated in : skeletally mature patient
excessive lateral laxity normal trochlea
‘Q’ angle is normal
TT-TG distance is < 20mm
low grade trochlear dysplasia
Contraindications : skeletally immature patients
where MPFL is normal

27. MEDIAL PATELLOFEMORAL LIGAMENT RECONSTRUCTION
Procedure
 Examination under anaesthesia
 Hamstring graft preparation
 Exposer of MPFL

28. MEDIAL PATELLO FEMORAL LIGAMENT RECONSTRUCTION
Procedure
 Patellar tunnel preparation
 Femoral tunnel preparation
 Femoral tunnel graft passage and fixation
 Graft passage through patellar tunnel and fixation
 Wound closure

29. DISTAL REALIGNMENT SURGERY
Fullkerson antero-medial tibial tuberosity transfer
aims to diminish the q angle or TT-TG distance with medialisation of tibial tuberosity and
unloads patello femoral articulation with anteriorisation of the tubercle
Indications
1. ↑ Q angle or ↑ TT-TG distance > 20mm
2. Patellar alta
3. Normal patellar glide
4. Medial facet arthritis
Contraindications
1. Skeletally immature patients
2. incompetent MPFL
3. Diffuse patellar arthritis

30. Fullkerson antero-medial tibial tuberosity transfer
Procedure
 Routine lateral retinacular release is done
 An oblique osteotomy is made from ateromedially close to anterior tibial crest
directed in postero lateral direction ,existing at lateral cortex posteriorly
 Mitek tracker drill guide with cutting slot is used to define precise osteotomy plane
 Bone pedicle is displaced in an antero medial direction usually about 12to 17mm
of anterization depending on obliquity of osteotomy

31. TROCHLEAR DYSPLASIA
 The normal trochlea is located in the anterior aspect of the distal femur. It is
composed of two facets divided by the trochlear sulcus
 The lateral facet is the biggest, it extends more proximally than medial facet and is
more protuberant in A.P. Aspect
 Dysplastic trochleas are shallow, flat or convex
 These trochleas are not effective in constraining mediolateral patellar
displacement
 Is defined by a sulcus angle > 140°

32. TROCHLEAR DYSPLASIA
Radiological features
X- ray lateral projection of normal trochlea will typically show the contour of
the facets, and posterior to them, the line representing the bottom of the
sulcus is visualized and is continues with the intercondylarnotch line

33. TROCHLEAR DYSPLASIA
Radiological features
Crossing sign
 The radiographic line of trochlear sulcus crosses he projection of the femoral
condyles
 The crossing point represents the exact location of the deepest point of trochlear
sulcus which is about 0.8mm posterior to a line projected from anterior femoral
cortex, in dysplastic trochlea it’s an point is 3.2mm forward to same

34. TROCHLEAR DYSPLASIA
Radiological features
Trochlear spur
the supratrochlear spur corresponds to an attempt to contain the lateral
displacement of the patella

35. TROCHLEAR DYSPLASIA
Radiological features
Double-contour sign
represents the hypo plastic medial facet, seen posterior to the lateral facet in
lateral view

36. TROCHLEAR DYSPLASIA
Classification of trochlear dysplasia
Type A: crossing sign +
the trochlea is shallower than normal, but still symmetrical and
concave
Type B: crossing sign +
supratrochlear spur +
the trochlea is flat or convex in axial view

37. TROCHLEAR DYSPLASIA
Classification of trochlear dysplasia
Type C: crossing sign +
double-contour sign +
supratrochlear spur –
representing hypoplasia of medial facet and lateral facet convex
Type D: crossing sign +
double-contour sign+
supratrochlear spur +
clear asymmetry of the height of facets, and referred to as a cliff pattern

38. MANAGEMENT OF TROCHLEAR DYSPLASIA
Surgical indications
 High grade trochlear dysplasia with patellar instability in the absence of
patellofemoral osteoarthritis
 Type of dysplasia should be identified when deciding the procedure
 Associated abnormalities including TT-TG distance, patellar alta, patellar
tilt should be identified and rectified
 MPFL reconstruction is always done
Contra indications
 Skeletally immature patients
 Associated osteoarthritis

39. MANAGEMENT OF TROCHLEAR DYSPLASIA
Type of dysplasia and surgical procedure
Type A dysplasia : medial patellofemoral ligament reconstruction
Type B and D dysplasia : sulcus deepening trochleoplasty with MPFL
reconstruction
Type C dysplasia : lateral facet elevation trochleoplasty with MPFL
reconstruction

40. MANAGEMENT OF TROCHLEAR DYSPLASIA
Procedure: sulcus deepening trochleoplasty by Henrey Dejour
 Indicated in type B and D trochlear dysplasia with patellar dislocation
 It is designed to establish a new trochlear groove of correct length and tilt
, addressing the root cause of patellar dislocation due to trochlear dysplasia
 The femoral trochlea is deepened by removing the subchondral trochlear
bone followed by incision, impaction, and fixation of cartilage flare along the
trochlear groove

41. MANAGEMENT OF TROCHLEAR DYSPLASIA
Procedure pre-operative post-operative

42. MANAGEMENT OF PATELLOFEMORAL INSTABILITY
A management algorithm is proposed for clinical use

43. CONCLUSION
 Patellofemoral instability can be difficult to treat
 Acute patello femoral dislocations should be treated with immobilization
and rehabilitation. Arthroscopy should be indicated for symptomatic
osteochondral injury
 In recurrent patellofemoral dislocations, it is important to understand
each patients reason for repeated instability.
 The reason can be determined through a detailed history, focused physical
examination, and radiographic studies including CT scan and MRI
 Once determined proximal realignment procedures, distal realignment
procedures, trochleoplasty or a combination of above procedures can be
tailored to the individual patient and be utilized to correct patellofemoral
biomechanics

44. Thank you