Vicente Sanchis-Alfonso, MD, PhDDepartment of Orthopaedic Surgery

Hospital Arnau de VilanovaValencia, Spain

UNDERSTANDING PATELLOFEMORAL PAIN

CONSENSUS MEETING

Role of Hypoxia in the Genesis ofAnterior Knee Pain

Anterior Knee Pain

LATERALRETINACULUM Infrapatellar

Fat Pad

INFLUENCING FACTORS

Gender Psychological Instability

Synovium

Subchondral Bone

Overload

ORIGIN

N = 12 knees

NOT ALL PFM ARE SYMPTOPMATIC

Symptomatic AsymptomaticSanchis-Alfonso et al, 2006

Why?

No relation between the result (satisfactory vs non-satisfactory) andthe presence or absence of PFM (χ2 = 0.025, p=0.875)

PFM18 / 21 - satisfactory result (85.7%)

3 / 21 - poor result (14.3%)

NO PFM14 / 16 – satisfactory result (87.5%)

2 / 16 – fair result (12.5%)

What have we learned from realignment surgery?

Sanchis-Alfonso et al, 2006

Pre-op Post-op 6 months Post-op 13 years

Satisfactory centralization at long-term follow-up in 16 cases (43.24%)

A RADIOGRAPHICAL PMF MAY NOT BE REAL

It could induce us to indicate a realignment surgery that could provoke an iatrogenic

PFM leading to a worsening of preoperative symptoms

Preop stress CT in extension

Postop stress CT in extension

Right

Right Left

Left

25 yo F / Medial Patellar Instability After Insall´s Proximal RealignmentPreop Gait Analysis

Postop Gait Analysis

We look PFM as representing internal load shifting within the patellofemoral joint that may

lower the threshold (i.e., decrease of the Envelope of Function) for the initiation and persistence of loss of tissue homeostasis

leading to the perception of patellofemoral pain. Pain always denotes loss of tissue homeostasis.

Hyperinnervation in the lateral retinaculum is a factor implicated in the pathogenesis of

anterior knee pain

Sanchis-Alfonso et al, 1998

Severe pain vs moderate-light pain (p = 0.03; F = 4.93)

Free nerve endings

Sanchis-Alfonso et al, 2000

Substance P immunoreactive nerves

Sanchis-Alfonso et al, 1998 & 2000

Innervation adopting mainly a perivascular location

Sanchis-Alfonso et al, 1998, 2000 & 2005

Severe pain (94%) vs moderate-light pain (30%) (p = 0.005)

We believe that homeostasis in the knee region ofanterior knee pain syndrome patients could be disturbed by

vascular problems

We hypothesize that periodic short episodes of ischemia due to vascular

bending could be implicated in pain in mostof the cases of young patients with anterior

knee pain syndrome

Sanchis-Alfonso et al, 2001, 2002 & 2005

Ischemia

NGF

HyperinnervationNGF

Lesions that produce ischemia

Sanchis-Alfonso et al, 1998, 2005

Lesions that are a consequence of ischemia (I)

Sanchis-Alfonso et al, 2005

Myxoid stromaldegeneration

Infarcted foci of theconnective tissue

Lesions that are a consequence of ischemia (II)

Sanchis-Alfonso et al, 1998, 2005

HypervascularizationWe have found higher values in the number of vesselsin the lateral retinaculum of patients with severe pain

than in those with moderate or light pain (p = 0.03; F = 4.58)

Factor VIII

Sanchis-Alfonso et al, 2005

2

1200

1000

800

600

400

200

0

12 0

000

8

6

40

2

Vascular innervationYes

No

Sanchis-Alfonso et al, 2005

VESS

ELS

IN 5

HO

T SP

OTS

PAIN SCORE1

n = 31

Immunohistochemistry (VEGF)

Sanchis-Alfonso et al, 2005

Western Blot

Sanchis-Alfonso et al, 2005

HypoxiaHypoxia

VEGFVEGF

HypervascularizationHypervascularization

NGFNGF

HyperinnervationHyperinnervation

Neural sprouting Neural proliferationin vessel walls

NeuronsNeurons

Ischemia

Role of hypoxia in the genesis of anterior knee pain

Clinical findingsSandow MJ, Goodfellow JW. The natural history of anterior knee pain in adolescents. J Bone Joint Surg 1985; 67-B: 36-38.

Selfe J, Karki A, Stvens D. A review of the role of circulatory deficit in the genesis of patellofemoral pain. Physical Therapy Reviews. 2002; 7: 169-172.

Selfe J, Harper L, Pedersen I, et al. Cold legs: a potential indicator of negative outcome in the rehabilitation of patients with patellofemoral pain syndrome. Knee 2003; 10: 139-143.

Gelfer Y, Pinkas L, Horne T, et al. Symptomatic transient patellar ischemia following total knee replacement as detected by scintigraphy. A prospective, randomized, double-blind study comparing the mid-vastus to the medial para-patellar approach. Knee 2003; 10: 341-345.

Naslund J. Patellofemoral pain syndrome. Clinical and pathophysiological considerations. Thesis. Karolinska Institutet. Stockholm. 2006.

Pathogenesis of Anterior Knee Pain

HypoxiaHypoxia

NGFNGFFree nerve endingsFree nerve endings Substance PSubstance P

PAINPAIN

Mast cellsMast cellsHistamineHistamine

HyperinnervationHyperinnervation

Prostaglandin E2Bone resorption

Thank You