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Patellofemoral Disorders


Wiberg’s Classification of patella shape:

(Descriptive only and has no correlation to pathological conditions)

Type I

Concave facets, symmetrical and equal in size (10%)

Type II

Medial facet is smaller. Lateral facet is concave (65%)

Type III

Medial is distinctly smaller with marked lateral predominance (25%)

 Patellofemoral kinematics

  • Patella increases the moment arm of the quadriceps thus increasing quad strength by 33-50%

  • The femur articulates only with a portion of the patella in each position of flexion, moving from proximal to distal with increasing flexion

  • Patellofemoral joint reaction force

    • 0.5 times body weight with walking

    • 3.3 times body weight with stairs



  • Determine if complaint is instability or pain

Examination (Also see Torsional Profile Assessment)

  • Standing examination

    • Varus/ valgus alignment

    • Examination of gait

    • Pelvic obliquity and leg length inequality

    • Q-angle

    • Femoral and tibial torsion

    • Miserable malalignment syndrome:

      • internal torsion of the femur, external torsion of the tibia and pronated feet

      • Position of subtalar joint. Pes planus.

  • Sitting examination

    • Grasshopper eyes appearance: high and lateral patellas

    • VMO atrophy

    • Lateral patellar tilt

    • Patellar tracking: pain and crepitation, 'J' sign

    • Position of the tibial tubercle with respect to the midline of the trochlea - Should lie < 20mm lateral to the midline of the femur

  • Supine examination

    • Q angle (Normal M 10° F 15)   

    • Quadriceps mass (VMO atrophy)

    • Hamstring tightness (popliteal angle)

    • Examination for medial plica

    • Tibial torsion

    • Tenderness on quadriceps or patellar tendon insertion, patellar facets, retinaculum tightness hamstrings, or heel cord

    • Crepitation and patellar compression

    • Apprehension test (20-30°flexion)                                           

    • Clarke's Snatch test (pain on contraction of the quadriceps with the patella fixed)

    • Patellar tilt (evaluates tension of the lateral restraint)

    • Patellar glide test (knee flexed 20 to 30°)

      • Decreased: 1 quadrant or less medial glide is indicative of tight lateral restraint

      • increased: subluxable, or dislocatable patella

  • Prone examination

    • Hip motion - femoral neck anteversion (abnormal if IR exceeds ER by more than 30°)

    • Quadriceps tightness - Ely test (especially rectus femoris)

    • Leg-heel alignment (Normal 2-3° of varus)

    • Hindfoot-forefoot alignment: (Normal: long axis of heel 90° perpendicular to transverse axis of forefoot)

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