Get a kick out of this: the spectrum of knee extensor mechanism injuries

Abstract

At the end of this article, the reader should be able to (1) recognise normal anatomy and anatomical variants of the extensor mechanism of the knee on various imaging modalities, including plain film, ultrasound and MRI; (2) diagnose a broad spectrum of EM injuries in adult and paediatric patients including patellar and quadriceps tendinopathy, Osgood-Schlatter disease, Sindig-Larsen-Johansson syndrome, chondromalacia patellae and patellar fractures on various imaging modalities; and (3) appreciate the important role of imaging in the diagnosis of musculoskeletal injuries. INTRODUCTIONThe extensor mechanism (EM) of the knee comprises the quadriceps muscles and tendon, the patella, patellar tendon and supporting retinaculum ( fi gure 1 ). Injuries of the EM are common and may be due to acute trauma, overuse injuries or chronic degenerative disease, and imaging plays an important role in diagnosis. In addition to clinical evaluation, abnormalities of bone and soft tissues can be visualised with plain fi lms and CT, and tendons can be assessed with ultrasound (US). MRI provides excellent evaluation of the knee and is often the imaging modality of choice in the characterisation of EM injuries. ANATOMY OF THE EM OF THE KNEEThe EM of the knee comprises the quadriceps muscles and tendon, the patella, the patellar tendon and supporting retinacula. The quadriceps muscles include the rectus femoris and the vastus lateralis, vastus intermedius and vastus medialis. The origin of the rectus femoris is the anterior inferior iliac spine, and the vastus muscles originate from the femoral shaft. The quadriceps tendon inserts on the superior pole of the patella and usually has a trilaminar appearance on MR. 1 The superfi cial lamina is composed of the rectus femoris, the intermediate lamina is composed of the vastus lateralis and medialis, and lastly the deep lamina is formed by the vastus intermedius.The patella is the largest sesamoid bone in the body and articulates with the trochlear groove of the femur. It usually possesses a median ridge that divides the proximal patella into medial and lateral facets, and the medial facet is generally smaller. The patellar tendon is mainly composed of rectus femoris fi bres that course over the patella and originates at the superior pole of the patella and inserts on the tibial tuberosity.The medial retinaculum has three components: the superior component is composed of the vastus medialis and patellofemoral ligament, the midportion is composed of the medial collateral ligament fi bres, and lastly the inferior component includes the patellotibial ligament and the medial patellomeniscal ligament. Similarly, the lateral retinaculum is composed of three parts: the superfi cial component includes the iliotibial tract and biceps femoris, the midportion is composed of the vastus lateralis, and the deep component is composed by the joint capsule.Additional soft tissue structures includes fat pads, namely the anterior suprapatellar (quadriceps) fat pad, the posterior suprapatellar (prefemo...

Patellar Tendinopathy: Clinical Diagnosis, Load Management, and Advice for Challenging Case Presentations

“…Clinically, plica may be painful with activities requiring only shallow knee flexion (eg, walking), whereas pain from quadriceps tendinopathy is provoked with activities requiring deep knee flexion. On MRI, whereas quadriceps tendinopathy may appear as diffuse thickening and increased signal of the distal quadriceps tendon at its insertion, 86 a clearly delineated lesion deep to the quadriceps tendon raises a high index of suspicion for the superior plica involvement. 43,79 The clinical presentation of localized osteochondral lesions of the inferior region of the patella or of the trochlea may sometimes closely mimic patellar tendinopathy.…”

Quadriceps tendinopathy — a forgotten pathology for physiotherapists? A systematic review of the current evidence-base

“…Houghton 21 19,25 This is supported by recent imaging studies 25 and a single-case report 23 which suggested that quadriceps tendinopathy is a distinct pathology, separate from jumper's knee and/or patellar tendinopathy. Magnetic resonance imaging (MRI) studies have differentiated the presentation of patellar and quadriceps tendinopathies, 19 and patients with quadriceps tendinopathy commonly present with pain at the insertion of the quadriceps tendon, therefore justifying why they should be considered two separate pathologies.…”

“…Magnetic resonance imaging (MRI) studies have differentiated the presentation of patellar and quadriceps tendinopathies, 19 and patients with quadriceps tendinopathy commonly present with pain at the insertion of the quadriceps tendon, therefore justifying why they should be considered two separate pathologies. 25 Prevalence Previous literature has acknowledged that there is a dearth of evidence pertaining to the epidemiology of most tendinopathies including quadriceps tendinopathy. 1 However, some limited literature does exist.…”

“…22 Imaging studies have suggested that quadriceps tendinopathy is less common than patellar tendinopathy. 25 Furthermore, its incidence is acknowledged as lower in the paediatric population, 21 although there is also no data to support this. 21 As with patellar tendinopathy, quadriceps tendinopathy is more commonly seen in people who participate in sports which stress the extensor mechanism of the knee such as volleyball, soccer, or basketball.…”

“…Both Tuong et al 25 and Pfirrmann et al 19 recommended the application of radiological investigations to Simpson assist in the diagnosis of quadriceps tendinopathy. Diagnostic ultrasound was used by Pfirrmann et al 19 as an adjunct to their clinical examination.…”