2. Anatomy
• The patella is a flat, triangular bone, situated on the front of the
knee-joint
• It is usually regarded as a sesamoid bone, developed in the
tendon of the Quadriceps femoris
3. Anatomy
The upper three quarters of the patella articulates with femur
and subdivided into medial and a lateral facet by vertical ledge
which varies in shape.
4. • Rectus femoris tendon : triangular in shape with insertion at
superior pole of patella.
• VMO tendon : Inserts obliquely at superomedial border of patella
only
a few mm in length; primary stabiliser of patella medially against VL
• Vastus Lateralis : Inserts obliquely At superior lateral aspect of
Patella,
Attachments around Patella
5. • Lat expansion of V. lateralis With a
superficial and deep layer forms the
Lateral retinaculum;
• Deep layer is the lateral
patellofemoral ligament :
• static guide for the patella
• decreases medial excursion
• increases the lateral
tracking.
6. MPFL
• Medial side also has a
patellofemoral ligament but
it is much weaker than
lateral side.
• hourglass-shaped
structure
• running from a
triangular space
between the adductor
tubercle, medial femoral
epicondyle and
gastrocnemius tubercle
• Inserts onto the
superomedial aspect of
the patella
8. No contact between the femur
and patella in full extension.
From extension to flexion, the patella
begins laterally and moves medially as
the patella enters the trochlear groove
and tibia derotates.
With flexion, patella enters the
trochlear groove from the lateral
side
Seats in the trochlear at ~20
degrees at this point the
congruence and compressive forces
provide stability
Patello-Femoral Articulation
9. Variations in area of contact:
Inferior Surface – first contacts at 20 degree
flexion
Mid Portion – 60 degree flexion
Superior portion – 90 degree flexion
Extreme flexion (> 120 degrees) – only medially and
laterally, quadriceps tendon articulates with trochlea
Patella femoral contact points
10. In flexion patella compressed
onto femur
creating joint reactive force.
Directly related to
quadriceps force
generation.
Increases as the angle of flexion
increases.
Joint reactive force
11. CAUSES OF PATELLA INSTABILITY
Soft Tissue
Global –
Hyperlaxity
Medial
MPFL
Insufficiency
VMO dysplasia
Lateral
ILIOTIBIAL BAND
Contracture
Lateral
retinaculum
Vastus lateralis
dominance
Osseous
abnormalities
Patella alta
Trochlea
dysplasia
Lower limb
Malalignment
Torsion
Fem anteversion
Ext tibia torsion
foot pronation
Genu Valgum
Increased Q
angle
TT:TG distance
12. Mechanism Of Injury
Indirect trauma: Internal rot. of
the femur on a planted foot
may cause patellar instability
Direct trauma: A laterally directed
force applied to the patella may
cause patellar instability
13. Acute Dislocation
Single episode after a significant trauma. Almost always lateral
dislocation
Recurrent Dislocation
Repeated, occasional dislocation (commonest form). The dislocations
may occur at intervals of weeks or months.
Habitual Dislocation
Also known as chronic dislocation patella which dislocates every time
the knee flexes.
In these cases it cannot be held in the reduced position throughout the
full range of flexion.
Types of dislocations
14. Recurrent Dislocation Habitual Dislocation
•Second decade
•Female preponderance /
Athletic males
•Initial episode of dislocation
•Subsequent episodes of
instability
•Frequency decreases with
Age (Crosby)
•The main factor is
incompetence of MPFL
•Knees in which patella
dislocates laterally each time
knee is flexed and returns to
midline in extension(Habitual
dislocation)
•More severe —patella
permanently dislocated —
(Permanent dislocation)
15. • Young
• Female
• Family history
• Bilateral
• Atraumatic disorders
• Anatomic abnormalities
Patella alta
Trochlear hypoplasia
TT-TG distance
‘Q’ angle
Quadriceps dysfunction
Hyper mobility
Predisposing factors responsible for recurrence
16. 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
17. Blumensaat’s Line
• line which corresponds to the
roof of the intercondylar fossa
of femur as seen on a lateral
radiograph of the knee joint
• The lower pole of patella lies
at the level of blumensaat’s
line
• The patella is located between
this line and a line projected
from growth plate scar
Patella Baja:
Abnormally low lying patella
18. • High-riding patella
• Too high above the trochlear fossa
• Occurs when the patellar tendon is too long
• Considered a main factor in patellofemoral misalignment as the
degree of flexion required is higher to engage in the trochlea,
compared to a normal knee
• leads to reduced patellar contact area and decreased bone
stability in shallow degrees of flexion
• About 25% of the patients with acute patellar dislocation have a
high-riding patella depicted on MR images
• Note- it is a normal anatomic variant that is asymptomatic in
most individuals
Patella Alta
19. Patella Alta: Patellofemoral
instability is often associated
Camelback sign: Prominence of
the infrapatellar fat pad
Grasshopper eyes: Proximal and
lat. Facing position of the patella
assoc. with patella alta and lat.
tilt
20. • Located in the anterior aspect of the distal femur.
• Two facets divided by the trochlear sulcus
• The lateral facet:
• Bigger
• Extends more proximally
• More protuberant in A.P. Aspect
• Dysplastic trochleas are shallow, flat or convex
• These trochleas are not effective in constraining mediolateral patellar
displacement
• Dysplasia Is defined by a sulcus angle >140 degree
• Trochlear dysplasia has been identified as one of the main
factors contributing to chronic patellofemoral instability.
Trochlear dysplasia
21. Type A: normal shape of the
trochlea, but a shallow trochlear
groove
Type B: markedly flattened or
even convex trochlea
Type C: trochlear facet
asymmetry, with too high lateral
facet, and hypo plastic medial
facet
Type D: type C features and a
vertical link between facets ('cliff
pattern') 3
Classification of trochlear dysplasia (Dejour
et al)
22.
23. Crossing sign
• Seen on true lateral plain radiographs of the knee when the
line of the trochlear groove crosses the anterior border of one of
the condyle trochlea.
• It is a predictor of trochlear dysplasia.
24. The double contour sign
• Seen on true lateral plain
radiographs of trochlear
dysplasia
• A double line at the anterior
aspect of condyles is seen if
medial condyle is hypoplastic
Trochlear spur
• The supratrochlear spur
corresponds to an attempt to
contain the lateral displacement
of patella
25. Fairbanks Apprehension Test
• Pain and defensive muscle contraction occurs on lateral patellar
displacement with 20˚ to 30˚ of knee flexion), indicates that lateral
patellar instability is an important part of the patient’s problem
• This test may be so positive that the patient withdraws the leg
rapidly when the examiner approaches the knee with his or her
hand, preventing thus any contact, or he or she grabs the
examiner’s arm.
26. • Patellar tilt test can also detect a tight lateral retinaculum, and should
always be carried out. In a normal knee, the patella can be lifted from
its lateral edge farther than the transepicondylar axis, with a fully
extended knee. On the contrary, a patellar tilt of 0˚ or less indicates a
tight lateral retinaculum.
• Lateral retinacular tightness is very common in patients with anterior
knee pain, and it is the hallmark of the excessive lateral pressure
syndrome described by Ficat.
Patellar Tilt
27. • Patellar tracking should be examined using
the “J” sign
• Patient seated on the examination table
with the legs hanging over the side and the
knees flexed 90˚, he or she is asked to
extend the knee actively to a fully extended
position
• Normally, the patella follows a straight line
as the knee is extended
• Patella runs proximally and laterally
describing an inverted “J” when
patellofemoral malalignment (PFM) is
present
“J” Sign
28. • To evaluate lateral retinacular
tightness
• Performed with the knee flexed 30˚,
and the quadriceps relaxed
• The patella is divided into four
longitudinal quadrants
• The patella is displaced in a medial
direction
• A medial translation of one quadrant
or less is suggestive of excessive
lateral tightness
• With this test pain is elicited over the
lateral retinaculum
Patellar Glide Test
30. • formed by intersection of a line from ASIS to
center of patella, and a center of patella to
middle of the tibial tubercle
• Normal Q angle --- males 8 -10 degrees
females ---15 +/- 5 degrees
• Increased in
• genu valgum
• external tibial torsion
• increase femoral anteversion
• laterally positioned tibial tuberosity tight
lateral retinaculum.
• Increase Q angle: more chance of recurrent
subluxation
Q angle
31. • The Q angle of the knee
increases with increasing
• Femoral neck anteversion
• External tibial torsion
• Physical exam. With Pt. in
supine position
• Observe the increased Q
angle
32. Imaging of the patellofemoral joint
• AP and lateral knee X-ray
• Axial - Merchants view and Laurin view
• MRI axial view
• CT rotational profile
33. The knee skyline- Merchant view
• Superior-inferior projection of the patella
• Ideal projection for patients that are better suited
in the supine position
The knee skyline -Laurin view
• Inferior-superior projection of the patella
• Best suited to patients able to maintain a semi-
recumbent position on the examination table
Axial views for Patella
34. System for describing the shape of the patella based mainly on asymmetry between the
patellar medial and lateral facet on axial views of the patella
• Type I: the facets are concave, symmetrical, and of equal size
• Type II: the medial facet is smaller than the lateral facet and flat or only slightly
convex
• The lateral facet is concave
• Type III: the convex medial facet is markedly smaller than the concave lateral facet
• Angle between the medial and lateral facets is nearly 90°
36. Insall-Salvati Ratio
• 30° flexed lateral knee x-ray
• A: patellar tendon length (TL):
length of the posterior surface of
the tendon from the lower pole of
the patella to its insertion on the
tibia
• B: patellar length (PL): greatest
pole-to-pole length
• Insall-Salvati ratio = A/B (or TL/PL)
• >1.2 patella alta
• <0.8 patella baja
37. Modified Insall-Salvati ratio
• 1=Distance from the inferior
margin of the patellar articular
surface (Instead of lower pole of
the patella in the original
index) to the patellar tendon
insertion
• 2=Length of the patellar articular
surface
• Modified Insall-Salvati ratio
= 1/2
• Normal value --1.25.
• Patella alta-- >2
38. Blackburne-Peel Ratio
• Done in x-ray with 30 degrees of flexion
• B= Measure distance along the patellar
articular surface
• A horizontal line at the level of the tibial
plateau is drawn
• A= Measure the distance between the
horizontal line and the inferior aspect of
the patellar articular surface
• Blackburne-Peel Ratio= A/B
• Normal 0.8
• Patella alta-- >1.0
39. Caton-Deschamp’s Index
Knee kept in 30 degree flexion
A= distance between the lower
articular surface of patella and
the anterosuperior tibial plateau
B= length of patellar articular
surface
Caton-Deschamp’s
Index= A/B
40. Why do we need a CT?
To look for
• Sulcus angle
• tilt
• congruence
• femoral trochlear depth
• Subluxation
• TT-TG distance
41. Femoral trochlear Depth
• Draw a line parallel to the
femoral condyles
• Draw a 2nd line parallel to the
first at the deepest point of the
femoral trochlea
• Draw a 3rd line parallel to the
highest points of the medial
and lat. aspects of the trochlea
• Measure btw. 2nd and 3rd lines
at the trochlear apex
42. Patellar Displacement
• Draw a line parallel to the
femoral condyles
• At 90° to the 1st line, draw one
line intersecting the patellar
apex
• Then draw a line bisecting the
trochlear apex
• The diff. btw. 2nd and 3rd lines is
the measurement of the patellar
subluxation
• If negative----patella is
medial to femoral trochlea
• If positive---- patella is lateral
43. Patellar Tilt Angle
• Draw the 1st line parallel to
posterior femoral condyles
• 2nd line parallel to the 1st at
patellar apex
• Patellar Tilt Angle is angle
btw. Lateral patellar facet and
the 2nd line
44. Congruence Angle (CA)
• Bisect the angle of femoral trochlea
• Draw a line from the apex of the
femoral trochlea through the apex of
the patella
• Congruence angle is angle btw. These
2 lines
• If CA is positive; patellar apex is
medial to trochlear apex
• If CA is negative: patellar apex is
lat. ,which implies patellar
displacement
45. CT classification of Malalignment
Type 1 - lateral subluxation without tilt
Type 2 - lateral subluxation with tilt
Type 3 - lateral tilt without subluxation
Type 4 - radiographically normal alignment
46. TT-TG
• Determines lateralization force acting
on patella through quadriceps muscles
• 2 axial CT-scan cuts are superimposed
• One at the level of proximal 3rd of
trochlear groove
• 2nd at superior part of tibial tuberosity
• TT-TG is distance (mm) measured btw
2 perpendiculars to the bicondylar axis
• 1st perpendicular passes through
the center of the tibial tuberosity
• 2nd passes through the center of
the trochlear groove
47. MRI Scan
• MRI can be used to diagnose prior patellar dislocations
on the basis of typical injury patterns
• In general, deformity of the infero media patella and
the lateral condyle, in conjunction with MPFL
disruption and patellar lateralisation, is diagnostic for
recent patellar dislocation
• More than two-thirds of the patients will show
osteo- chondral lesions of the medial patella
48. MRI following an acute dislocation showing a
torn medial retinaculum
49. Management
•Non Operative management Tobe attempted in all patients
•Goals
•Normal flexibility
•Balanced quadriceps strength
•Stretching of tight lateral structures
• Push back w/o difficulty
• Jt aspiration and immobilization in full extension for 3
weeks with knee brace
• If no sign of soft tissue lesion
• Retained for 2-3 weeks
• Quadriceps strengthening exercises for 2-3 months
50. Treatment of Patella Instability
Always conservative first
1.Quadriceps strengthening
2.Core stability
3.Mc Connell taping
4.Insoles
51. Quadriceps Training
• Most Essential component
• Strengthening of quadriceps especially VMO
• Isometric and progressive resistance exercises
with knee in extension
• With increasing strength, short arc exercises in
last 30°
52. • 2 strips of tape are applied to fully cover the patella,medial and lat.
Femoral condyle
• 3rd piece of tape is applied from center of patella, pulling toward
the medial side of the knee and anchored behind medial fem.
condyle
Indications
With certain knee injuries – such as patellofemoral pain syndrome
where abnormal patella tracking is contributing to the injury.
Toprevent injury or injury aggravation – Patella taping maybe
beneficial during sports or activities that place the knee at-risk of
injury or injury aggravation
Mc Connell
patella
taping
53. Surgical treatment
Surgery in acute patella dislocation is indicated in
1. Osteochondral fracture
2. Loose body formation or joint incongruity
3. Incompetency of MPFL
Removal of loose bodies and MPFL repair required in these conditions.
Complications
• Recurrent dislocation
• Anterior knee pain
• Knee swelling
• Recurrent haemarthrosis
54. Recurrent Patellofemoral dislocation management
If dislocation of the patella continues despite appropriate
nonoperative treatment, surgery is indicated
Otherwise, the patient may become apprehensive and afraid to use
the knee,and with continued recurrence the joint may be severely
damaged
More than 100 surgical procedures have been described for the
treatment of patellofemoral instability
The key to successful surgical intervention is correctly identifying and
treating the pathologic anatomy producing the instability.
55. The surgical procedures for recurrent Patellar instability are
classified into proximal and distal realignment
The operation involving structures above the knee cap are termed
as Proximal and if involves structures below are termed as Distal.
Proximal realignment of extension mechanism
1. MPFL reconstruction
2. Lateral retinacular release
3. Medial plication / reefing
4. VMO advancement
Distal realignment of extensor mechanism
1. Medial or antero medial displacement of tibial tuberosity
56. Pathology Diagnosis Procedure
Bony
Patella alta Insall Index.1:2 Distalisation
Trochlear Dysplasia Crossing sign MPFL reconstruction
Trochlear Spur Trochleoplasty
Allignment
Tibial tubercle Q angle >20 degree,
TT-TG>20mm
Antero medialization of tibial
tuberosity
Femoral Anteversion Thigh –foot Angle >30 degree Rotational Osteotomy
Soft Tissue Imbalance
Dynamic (VMO dysfunction) TT-TG<20 mm Rehabilitation
Static
Incompetent MPFL Lateral glide 3 quadrants Medial Imbrication if good
tissues or MPFL
reconstruction
57. Surgical Procedures for treatment
of patellar instability
Indications
LOW RISK –LOW REWARD
Medial Repair/Imbrication • First dislocation+ repairable chondral defect
• Instability in skeletally mature
• In combination with distal realignment
Lateral Release Excessive lateral pressure syndrome
In combination with realignment procedure
when excessive tightness prevents patellar
centering
LOW RISK-HIGH REWARD
MPFL reconstruction Recurrent MPFL deficiency +_ trochlear dysp.
Elmslie-Trilat Procedure Instability
TT-TG> 20 mm +strong repairable medial
structures
58. Surgical Procedures for treatment
of patellar instability
Indications
HIGH RISK-HIGH REWARD
Fulkerson distal realignment • Symptomatic lateral facet + distal pole
arthritis+ TT-TG >20 mm
• Contraindicated in proximal/medial facet
arthritis
• High risk of proximal tibial fracture with
sports
Rotational high tibial osteotomy • Instability +severe rotational deformity
Trochleoplasty • Dysplastic trochlea
• Risk: osteonecrosis
• DJD
• Arthrofibrosis
Grooveplasty Risk: DJD
3-in-1 procedure– extensor mechanism Recurrent instability
59. 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.
Medial Patello femoral ligament Reconstruction
60. Indicated in
• skeletally mature patient
• excessive lateral displacement
• normal trochlea
• ‘Q' angle is normal
• TT-TG distance is < 20mm
• low grade trochlear dysplasia
Contraindications
• skeletal immaturity
Medial Patello femoral ligament
Reconstruction
61. • Examination under anaesthesia (EUA)
• Diagnostic Arthroscopy: Superolateral portal
• Graft Harvest & preparation
• Incision 1: on medial side patella
• Incision 2: on femoral fixation site
• Patellar side fixation
• Graft passage from incision 1 to 2
• Femoral side fixation
• Appropriate tensioning
Surgical Steps
62. • Gracilis (G): stiffness closer to MPFL
• Semitendinous (ST)
• Medial patellar tendon (PT)
• Adductor tendon (AMT)
• Quadriceps tendon (QT)
• Allografts
• Artificial tendons
• One end of the graft may be left attached; ex: ST
tibial attachment, AMT femoral attachment, QT
patellar attachment
Graft source
63.
64. • A line is drawn extending distally from the
post. femoral cortex (line 3)
• Two lines are drawn perpendicular to line 3
• 1st intersecting the point where the
margin of the medial condyle meets the
posterior cortex (line 1)
• 2nd intersecting the most posterior point
of Blumensaat's line (line 2)
• A circle of 5-mm diameter is drawn
contacting the line drawn from the
posterior cortex
• The MPFL femoral insertion should fall
within this circle
Schottle’s point
65.
66. Appropriate tensioning
• The ideal tension at the time of fixation of the graft
is unknown.
• The ligament functions as a check rein in early
flexion (0 to 30 degrees) and is therefore under the
greatest tension in this range of knee flexion. It is
logical to fix the graft with the knee at 30 to 40
degrees flexion.
• The patella should not be pulled medially by the
reconstructed ligament but lateral translation
beyond the lateral margin of the trochlear should be
prevented.
67. • Prominence of fixation hardware on the medial aspect
of the medial femoral condyle: local irritation and
potentially restrict motion
• Patellar fracture: usually relates to the use of bone
tunnels; penetration of the anterior cortex
• Recurrent lateral patellar dislocation: predisposing
factors such as patellar alta, trochlear dysplasia, and
lateralization of the tibial tuberosity, as well as the
overall alignment of the lower limb
• Infection
• Hematoma formation
• Graft site morbidity
Complications
68. Indication
1)Tight lateral structure preventing patellar centring
2)Lateral patellar pressure syndrome
3)Can be done in skeletally immature patients
Release to include
1)Lateral retinaculum from distal third of vastus lateralis
2)Lateral patellofemoral ligament
3)Lateral patellotibial ligament
Lateral Release
Can be done open or arthroscopy procedure (preferred now a days)
69. Lateral Release
1. The planned skin incision
3. The retinaculum is visualized
2. The Lat. Retinaculum is divided with
scissors
70. Complications of Lat. release
• Extensive release may lead to medial subluxation of the
patella
• Infact medial patella subluxation or dislocation is almost
always iatrogenic 2° to an overzealous lateral release
• Injury to superolateral geniculate vessel
Results varied
• good results in short term
• poorer in long term
71. • MPFL and the VMO are the primary restraints to lateral patella
translation
• particularly early in flexion before full trochlear engagement.
• 3 types of 1° procedures for medial repair
(1)Plication of the medial patellar retinaculum.
(2)Anatomic repair of the MPFL, and
(3)Anatomical repair surgery of the VMO.
Medial Repair
72. Medial reefing and lateral release
NAM AND KARZEL
A. Arthroscopic lat. Release and
mini-open medial reefing
A. Mattress sutures used to reef vastus
medialis and medial retinaculum
73. Distal Realignment Surgeries
Aims to diminish the Q angle or TT-TG distance with
anteromedialisation of tibial tuberosity and unloads
patello femoral articulation
Indications Contraindications
1. Increased Q angle or TT-
TG distance > 20mm
1.Skeletally immature patients
2. Patellar alta 2.incompetent MPFL
3. Normal patellar glide 3.Diffuse patellar arthritis
4. Medial facet arthritis
74. ELMSLIE-TRILLAT OPERATION
Medial repositioning of the
patellar tendon, along with lat.
Release and medial imbrication
while avoiding post. Placement
of tibial tubercle
a. The planned skin incision
and lat. Retinacular release
b. The tibial tubercle is
elevated
c. Medial placement of tibial
tubercle
d. Axial view of the medialized
tibial tubercle
75. Fulkerson Osteotomy
(a,b) Anteromedialization is an
obligue osteotomy of the tibial
tubercle
(c,d) The slope of the osteotomy
determines the degree of
anteriorization
(e,f) The tubercle is elevated with
an osteotome and when in proper
position , is secured with 2 screws
76. HUGHSTON PROCEDURE
• Proximal realignment and distal tibial tubercle transfer is done
a. The planned incision for medial arthrotomy and lateral
release extend to the tibial tubercle
b. The tibial tubercle is transferred medially (arrows)
c. The transferred tibial tubercle is securely fixed and the VMO is
advanced laterally at the time of closure (arrows)
77. 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
Management of Trochlear dysplasia
78. 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
Management of Trochlear dysplasia
79. DeJour sulcus deepening Trochleoplasty
• Removal of subchondral bone and reshaping of trochlear
groove is done
• Fixation of new trochlea is done using 2 staples
80. Closing wedge osteotomy of patella
a. Closing wedge osteotomy of the patella
b. The osteotomy is securely fixed with a screw
81. Derotational High tibial osteotomy
• Proximal tibia reduced without posterior or
medial subluxation and fixed using 2 or 3 step
staples
• One staple is placed perpendicular to other to
prevent loss of rotation
INDICATIONS
1) Femoral ante-version(thigh foot angle>30
degree)
2) External tibial torsion
3) Tubercle sulcus angle more than 10 degree.
82. INSALL “TUBE” REALIGNMENT TECHNIQUE.
a. The planned incision for the lat. Retinacular release and the medial
arthrotomy
b. The lat. Border of the quadriceps tendon is sutured to the medial
flap
c. This creates a tube proximally and realigns the patella
84. CAMPBELL’S PROCEDURE
• A proximal medial sling is created here
A. A free flap of the medial retinaculum is dissected free maintaining a
proximal attachment
B. The medial defect is closed and the medial retinacular flap is
passed beneath the quadriceps tendon(QT)
C. The flap is the brought back over to QT
85. THE GALIAZZI PROCEDURE
a. The semitendinosus tendon is passed through an obligue drill
hole in the patella
b. Brought back medially to its insertion