1. Hiren M Divecha (ST4)
ELHT
1/5/2012

2. Overview
1. Anatomy
2. Acute dislocation
3. Chronic Instability

3. Patella Instability Spectrum

4. Joint geometry
 Lateral facet 1cm higher
(restraint in ext)
 Trochlea groove (engages
from 10-20° flex)
 Joint position
 Q angle largest in ext.
(tibia ext rotates)

5. Soft Tissue
 Retinaculae
 Lateral
 Medial
 MPFL
 50-60% static resistance till 20° flex (Conlan et al. JBJS
Am 1993)
 Quads/ patella tendon (in flexion)
 Dynamic muscle balance
 VMO

7. Acute Dislocation
 History
 Flexion, femur internally
rotated, quads contract
 Rarely direct trauma
 Almost always laterally
 Usually reduces on knee
extension
 Examination
 Effusion
 Tenderness – medially
 Defect in medial
retinaculum-VMO
 Exclude other soft tissue
injuries

8. Acute Dislocation
 Investigation
 Aspiration
 Pain relief
 Fat droplets suggest osteochondral #
 X-rays
 AP/lateral/Merchant views
 Exclude osteochondral fractures
 Avulsion from adductor tubercle
 MRI
 Assess osteochondral/ chondral injuries
 MPFL tears

11. Acute Dislocation
 Treatment
 Gentle closed reduction
 Extension + medial force
 Cricket pad splint 2-3
weeks
 Physio
 Quads strengthening esp.
VMO
 ROM
 Proprioceptive feedback
 ? Acute MPFL repair

12. Acute Dislocation
 Osteochondral #s
 Small – excise
 Large – fix
 Conservative
 20-40% redislocation (Cofield & Bryan. J Trauma 1977)
 Assoc. with <20yrs age + anatomical factors
 40-60% persisting anterior knee symptoms/ instability symptoms
 Atkin et al. Am J Sports Med 2000
 Acute MPFL repair
 ? Reduced redislocation rate
 Nikku R et al. Acta Orthop 2005. 7yr. No diff
 Palmu S et al. JBJS Am 2008. 14yr. No diff

13. Chronic Instability
Clinical Radiological
 Previous history, female, >20yrs  Patella alta
 Apprehension test  Patella tilt
 Lateral tightness
 Hypoplastic lateral femoral
 Q angle >15°
condyle
 Mal-tracking (J sign)
 Femoral anteversion/ internal  Trochlea dysplasia
torsion
 Tibial torsion (ext)  CT – increased TT-TG
 Genu valgum >20mm
 VMO wasting
 Soft tissue laxity

14. Clinical
Apprehension Test Patella glide

15. Clinical
Patella Tilt J-sign

16. Q angle

17. Patella Alta

18. Sulcus angle Patella tilt

19. Normal lateral

20. Trochlea dysplasia (Dejour)

21. TT-TG Distance (CT)

22. Treatment
 Physio
 Quads/ VMO strengthening
 Proprioceptive feedback
 (Taping makes no difference)
 Surgery
 Consider if failure with conservative
 > 100 procedures!
 Identify & treat underlying patho-anatomy

23. Soft Tissue Procedures
 Lateral release
 Effective for patellar tilt (LPCS)
 Ineffective by itself for instability (Lattermann et al. Sports
Med Arthrosc 2007)
 Combine with medial procedures or ossesous realignment
 Medial tissue reefing/ VMO realignment
 MPFL reconstruction
 Low Q-angle
 Autograft (hamstring, IT band, add mag), LARS
 Good outcomes (sys rev. Smith et al Knee Surg Sports
Traumatol Arthrosc 2007)

25. Tibial Tubercle Transfer
 Medialise
 Abnormal Q-angle/TT-TG
 Anteriorisation
 Reduces contact pressure
 Distalise
 Patella alta
 Risk of #
 Good outcomes
 Poor if chondral damage
exists

26. Fulkerson Osteotomy

27. Tibial Tubercle Distalisation

28. Trochleoplasty (Dejour)
 For trochlea dysplasia
 Cancellous bone
removed to deepen
sulcus
 Risk of articular damage,
post-op OA
 Good results (but some
develop OA)
 Von Knoch et al JBJS Br
2006

29. Summary
 Can be a difficult problem to understand
 Identifying patho-anatomy key to planning treatment

30. Questions?

31. Reading References
 Colvin AC, West RV. Current Concepts Review:
Patellar Instability. JBJS Am 2008, 90(2): 751-62
 Minkowitz R, Inzerillo C & Sherman OH. Patella
Instability. Bull NYU Hosp Jt Dis 2007, 65(4): 280-93
 Boden BP et al. Patellofemoral Instability:
Evaluation and Management. JAAOS 1997, 5(1): 47-
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