Stephen R. Christian, MD, M. Bret Anderson, MD, Ronald Workman, MD, William F. Conway, MD, FACR, Thomas L. Pope, MD, FACR*
Department of Radiology, Medical University of South Carolina, PO Box 250322, 169 Ashley Avenue, Charleston, SC 29425, USA
Anterior knee pain (AKP) is a common complaint in primary care and orthopedic clinics. In fact, in the sports medicine clinic, up to 25% of patients with knee complaints have symptoms of anterior knee pain . Adolescent females and other young individuals are at particular risk for AKP. In these individuals, symptoms are usually related to increased use, frequently because of increased sports participation . AKP among school-age students has been reported to be 3.3% in the 10- to 19-year age group, and the incidence was 10% among 15 year olds . Symptomatic individuals are more likely to be involved in competitive sports than age-matched controls . Another group with a higher incidence of AKP is older females, and their major risk factors are lack of conditioning, previous trauma, and degenerative changes .
The anatomy of the patellofemoral joint is complex. The patella is the largest sesamoid bone in the body and its articular surface is covered by thick cartilage. The length of the patella is somewhat longer than its articular surface, with the ratio being normally about 1.2 to 1.5. In full extension, the patella lies just proximal to the trochlea, often with a slight lateral position. The patella engages the trochlea at about 10 to 15 degrees of flexion, and stays engaged throughout flexion above 15 degrees . The trochlea is the indentation on the anterior surface of the distal femur, just proximal to the intercondylar notch. It too is covered in cartilage. The sulcus angle is the angle of indentation and is an important factor in patellofemoral joint stability (Fig. 1). This angle increases down the length of the trochlea. The patella is secured in place by the soft tissue structures of the knee. The medial retinaculum and patellofemoral ligaments provide medial restraints. The lateral retinaculum is the confluence of the iliotibial band and the lateral patellofemoral ligament. These structures provide lateral restraint. The quadriceps muscle is made up of the rectus
*Corresponding author. E-mail address: [email protected] (T.L. Pope).
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