MRI features of a quadriceps tendon rupture.

To cite: Ni Fhoghlu C, Ellanti P, Moriarity A, et al. BMJ Case Rep Published online: [please include Day Month Year] doi:10.1136/ bcr-2015-209942 DESCRIPTION Quadriceps tendon (QT) ruptures are uncommon injuries that predominantly affect middle-aged men. Ruptures occur as a result of direct or indirect trauma to the knee with a powerful eccentric contraction of the QT being the most frequent cause of the rupture. Degenerative changes associated with ageing have been shown to be a factor with QT ruptures. Spontaneous QT ruptures have been shown to be associated with predisposing conditions such as diabetes, chronic renal failure, gout and quinolone antibiotic use among others. The diagnosis of QT ruptures are frequently missed or delayed. Clinical features of QT ruptures include the triad of pain, loss of extension and a supra patellar gap. However, clinical examination may be limited by both pain and swelling leading to a high rate of missed diagnosis. Radiographic features include obliteration of the quadriceps shadow, a supra patellar soft tissue mass due the retracted tendon and an osseous avulsion fragment from the proximal pole of the patella. A low-riding patella or patella baja is another feature suggestive of a QT rupture (figure 1). The Insall-Salvati index which is a ratio of the patella tendon length to the patella length on the lateral radiograph is useful in detecting a low-riding patella or patella baja when the index is <0.8. Ultrasonography has been shown to be a better modality than radiographs for diagnosis of QT ruptures. It is inexpensive and dynamic, but is operator dependant. MRI is better but is limited by its availability and high cost (figure 2).