Patellar and Quadriceps Mechanism
The extensor mechanism of the knee is composed of the quadriceps muscle group and tendon, the patella, the patellar ligament, the tibial tubercle and the patellar retinaculum. The patellofemoral articulation centralizes the entire mechanism on the anterio
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CONTENTS 13.1 Introduction 217 13.2 Anatomy 218 13.2.1 Soft Tissue Stabilizers 219 13.3 Biomechanical Considerations 221 13.3.1 Patellar Tracking and the Q Angle 222 13.4 Clinieal and Pathologie Considerations 223 13.4.1 The Request for Imaging - History and Physieal Examination 223 13.5 Routine Radiography 224 13.5.1 Lateral View 224 13.5.2 Posteroanterior View 225 13.5.3 The Standing Axial View 225 13.5.4 The Supine Axial View 226 13.5.5 Radiographie Measurement of the Axis of the Knee 227 13.6 Roentgen Stereometrie Analysis 228 13.7 CT and MR Imaging of Patellar Tracking 229 13.7.1 Measurements 229 13.7.2 The Femoral Trochlea and Patellar Tracking 230 13.7.3 Summary of Radiologieal Measures of Patellar Tracking 233 13.8 Osteoarthrosis of the Patellofemoral Joint 235 13.8.1 Imaging of Patellofemoral Osteoarthrosis 237 13.9 Traumatie and Overuse Conditions 238 13.9.1 Patellar Dislocation 238 13.9.2 Recurrent Dislocation of the Patella 241 13.9.3 Overuse Syndromes 243 13.10 Conclusion 244 References 245
13.1
Introduction The extensor mechanism of the knee is composed of the quadriceps muscle group and tendon, the patella, the patellar ligament, the tibial tubercle and the patellar retinaculum. The patellofemoral articulation
N.EGUND,MD Professor, Department of Radiology, Aarhus University Hospital, Noerrebrogade 44, 8000 Aarhus C, Denmark L.RYD,MD Associate Professor, Department of Orthopedies, University Hospital of Lund, 22185 Lund, Sweden
A.M. Davies et al. (eds.), Imaging of the Knee © Springer-Verlag Berlin Heidelberg 2003
centralizes the entire mechanism on the anterior surface of the femur, and during knee extension it mediates the forces generated by the largest muscles through the largest lever arms in the body. Minor variations in each component of the extensor mechanism may affect the centralizing function of the patellofemoral joint by altering the patellar tracking in the sulcus of the femur and resuIt in patellofemoral pain and joint degeneration. In spite of extensive experimental and clinical research, the problems of the patellofemoral joint remain achallenge to clinicians, and without a clear understanding of why patellar disorders occur it is not surprising that there is no consensus on how to treat them (THOMEE et al. 1999). Neither the widespread use of arthroscopy nor the availability of newer diagnostic imaging techniques such as ultrasound, computed tomography (eT) and magnetic resonance (MR) imaging has so far contributed significantly to the understanding of disorders related to dysfunction of the extensor mechanism or to the traditional treatment of patellofemoral disorders (INSALL 1995). Clinical assessment and imaging of the normal and injured patellofemoral joint require knowledge not only about the anatomy and biomechanics of the knee and the extensor mechanism, but also about the site and pathoanatomical characteristics of the different disorders in question. In each clinical situation, the (MERCHANT 1988) classification system of patellofemoral dis orders (Table 13.1) may be us
