This document discusses patellofemoral joint instability. It begins by outlining causes of instability including soft tissue factors like muscle imbalance or MPFL insufficiency, as well as bony abnormalities. Assessment techniques are described like evaluating alignment, patella tracking, and imaging. Treatment options are then covered including conservative care, realignment procedures like tibial tubercle transfer, and soft tissue reconstruction like MPFL repair. Specific techniques are outlined for addressing issues like patella alta or trochlear dysplasia. The importance of individualizing treatment based on each patient's anatomy and needs is emphasized.

1. Professor Deiary F Kader
Department of Sport, Exercise, Northumbria University, Newcastle
www.oasir.co.uk
Knee Surgeon, Nuffield Hospital, Newcastle upon Tyne
PATELLOFEMORAL JOINT INSTABILITY
PostGrad Orth Deiary Kader

2. Postgraduate Orthopaedics
FRCS(Tr&Orth) Revision Course
Newcastle Upon Tyne 16-21 March 2015
•
Professor Deiary Kader
Consultant Orthopaedic & Trauma Surgeon
Knee Surgeon
Nuffield Hospital Newcastle
NGMV Charity

3. PLAN
Presentation
Frank dislocation
Subluxation
Symptomatic instability
Pain due to mal-tracking

4. PATELLAR DISLOCATION
Re-dislocation rate
First Time 17-20%
Second Time 44%-71%
High dissatisfaction following
conservative Rx

5. PFJ BIOMECHANICS
Patellofemoral joint reaction force
WALKING 0.5xBW
STRAIGHT LEG RAISE 0.5xBW 0 DEG
CYCLING: 1.2 × BW
RISING FROM A CHAIR w ARMS: <3 × BW
STAIRS (UP OR DOWN) 3.3xBW 60 DEG
JOGGING & SQUAT–RISE 6xBW at 140 deg
SQUAT–DESCENT 7.6x BW at 140 deg
JUMPING UP TO 12 × BW
Ff
Ft
Fj
Trigonometry
Fjf=Ff cos(angle/2)
PostGrad Orth Deiary Kader

6. PATELLAR STABILITY
DETERMINED BY
– Soft Tissue 0-300
Muscles
Ligaments MPFL (at 200-300)
– Bone morphology >300

7. CAUSES OF PATELLA INSTABILITY
• Soft Tissue
• Global --HMS (Hyperlaxity)
• Medial
• MPFL Insufficiency
• VMO dysplasia/VL dominance
• Lateral -- ITB, Contracture Lat Ret
• Osseous abnormalities
• Patella alta/ morphology
• Trochlea dysplasia
• Lower limb Malalignment (Torsion or Genu Valgum)
– Fem anteversion, Ext tibia torsion, foot pronation
– Increased Q angle or TT:TG distance
• Gait (Valgus thrust, Pelvis core muscles)

8. WHY THE PATELLA IS UNSTABLE
Lower limb Malalignment??
– Femur, tibia or foot pronation
Osseous abnormalities??
– Patella alta
– Increased Q angle
– Trochlea dysplasia
Soft Tissue??
– HMS
– MPFL Insufficiency
– Muscle or ITB
Gait ??
PostGrad Orth Deiary Kader

9. KNEE ASSESSMENT
Leg Alignment Varus/valgus
Soft tissue imbalance
Ligament assessment (ACL,PCL, MCL, LCL)
Meniscal assessment
Medial/ Lateral compartment OA
Hip , Spine, peripheral pulses
Apprehension test

10. PATELLA ASSESSMENT
Beighton Score0---9
Patella Alignment (Q Angle)
Dislocation in extn (J Sign)
Quads Bulk/ ITB (Ober's test)
Hamstring Tightness
Patella height Alta/Baja
Patella Mobility (N@300=<1/2)
Parapatellar tenderness
Patella Apprehension
PFJ Crepitus
PFJ Compression (Clarke test)
Trochlea Depth Normal (1380)
– Shallow ,Flat , Convex , Cliff

11. Many potential problems
• Crude measure
• How it is measured?
– Flexion, Extension
– Standing, Sitting, Supine
– Muscle relaxed/tense
• No standard method
Q- Angle

12. IMAGING OF THE PATELLOFEMORAL JOINT
AP and Lateral Knee x-ray
Merchant’s view
MRI Axial view
CT Rotational Profile
Merchant’s

13. Trochlea
dysplasia
Blumensaat's line
Normal Trochlea
Depth
NORMAL

15. MEASURING PATELLA HEIGHT
Caton – Deschamps
index =1.2
Blackburne-peel
index = 1.12
PostGrad Orth Deiary Kader

16. MPFL injury
Patella pain
Articular Damage
MRI SCAN

17. ROTATIONAL PROFILE CT
EVIDENCE BASED INTERVENTION
1. Femoral Anteversion N=50 -150
2. Knee rotation N=30
3. External Tibial torsion 250-300
4. TT:TG offset (N= 10-19mm)
5. Patella index
6. Patella Tilt (N=average QD&QC <200)
7. Trochlea Tilt (N>130)
8. Trochlea DepthNormal (1380+/- 60)

18. TRUE Q ANGLE, MEASUREMENT OF THE TIBIAL TUBEROSITY-TROCHLEAR GROOVE (TT/TG)
DISTANCE
Normally TT/TG = 2-9 mm
pathologic measure is > 19 mm
PostGrad Orth Deiary Kader

19. HOW USEFUL IS TT:TG
• Large variation in normal value (patient size and height)
• Poor interrater reliability 3-5mm measurement error
– Trochlea ?deepest point of
– Tib Tub bony landmark vs Central point of PT attachment
4mm
• What condition?
– Flexion or extension
– Weight bearing  5mm
• MRI or CT measurement

20. TREATMENT OF PATELLA INSTABILITY
Conservative first
Quads strengthening
Core stability
McConnell Taping
Insoles
Gait

21. Med Epicondyle
Add Tubercle
Patella
MPFL
PostGrad Orth Deiary Kader

22. PostGrad Orth Deiary Kader

23. BONY TUNNEL
PostGrad Orth Deiary Kader

24. MX OF PATELLA INSTABILITY
Patellofemoral Instability with Malalignment
Distal Realignment
tibial tubercle transfer
Combined
MPFL Recon

25. FULKERSON'S TECHNIQUE OF ANTEROMEDIALIZATION
A steeper osteotomy plane will produce more
anteriorization along with medialization

26. OTHER PATELLOFEMORAL PROBLEMS
Patella Alta
– Distal transfer (Distalization)
Trochlea Dysplasia
– Trochloplasty
PostGrad Orth Deiary Kader

27. 1.4 cm
Patella alta

31. TROCHELOPLASTY

32. TAKE HOME MESSAGE
The approach to patellar instability should be
individualised and tailored to each patient’s
symptoms, anatomy and physical demands

33. PostGrad Orth Deiary Kader

34. 24 years old female doctor
had a permanents
dislocation of the patella
Treated with
1. Lateral release
2. Tib Tub Medialisation
3. Tib Tub Distalisation
4. Trochleaoplasty
5. MPFL Reconstruction
PostGrad Orth Deiary Kader

35. TREATMENT SUMMARY
MPFL Reconstruction (very popular >80%)
Tib Tub Medialisation on the decline
Tib Tub Distalisation excellent procedure
Trochleoplasty
Distal femoral Osteotomy

36. THANK YOU