Quadriceps Tendon Rupture Workup

Updated: Jun 08, 2021
  • Author: James Edwin Lyle, MD; Chief Editor: Thomas M DeBerardino, MD  more...
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Laboratory Studies

A preliminary laboratory workup to rule out rheumatologic, endocrine, and renal disease may be indicated in suspicious, presumably healthy individuals with quadriceps tendon ruptures.

Consider a laboratory workup in all cases of bilateral rupture.


Plain Radiography

Several imaging studies are helpful to confirm the diagnosis of quadriceps tendon rupture. [42]  Plain radiography is usually the first imaging modality ordered. [37]

Several abnormalities may be seen on lateral radiographs. These include obliteration of the quadriceps tendon shadow, a suprapatellar mass, suprapatellar calcific densities, spurring of the anterior superior patella, joint effusion, patella baja, and anterior tilting of the superior patella. These findings may be quite subtle or even absent. Patella baja is diagnosed by using the Insall-Salvati index, which is the ratio of the patellar tendon length to the length of the patella. This ratio should near 1, with no more than 20% variation.

On the axial view, the tooth sign, which represents vertical ridging of the osteophytes at the quadriceps insertion, may be seen on the anterior patella (see the image below). In 1977, this sign was first described by Greenspan et al as an incidental finding caused by tendon degeneration [43] ; in 1980, Kelly et al first reported it in association with a quadriceps tendon rupture. [44]

Toothlike ridging of the anterosuperior patella. R Toothlike ridging of the anterosuperior patella. Reproduced with permission from Greenspan A, Norman A, Tchang FK. "Tooth" sign in patellar degenerative disease. J Bone Joint Surg Am. Jun 1977;59(4):483-5.

Use other imaging modalities next to clarify a questionable diagnosis or to differentiate complete and incomplete ruptures.



In complete ruptures, arthrography reveals extravasation of contrast material from the suprapatellar bursa into the soft tissues anterior to the patella, but it is an invasive procedure. [45, 46]



Ultrasonography (US) has high sensitivity and specificity in depicting complete quadriceps tendon ruptures. [47]  An area of hypoechogenicity is seen across the entire thickness of the tendon. In partial tears, a focal hypoechoic defect is seen. In tendinitis, tendon thickening is visualized. US is quick and noninvasive, but its accuracy is highly operator-dependent.

Ultrasound elastography (USE) evaluates mechanical properties of tissues (including tendons) by characterizing their response to stress. There are two major techniques, compression elastography (CE) and shear-wave elastography (SWE). Both techniques have been used for the assessment of the quadriceps tendon. [48]  USE may have greater sensitivity and diagnostic accuracy in tendinopathy than conventional US and may detect pathologic changes before they are visible on conventional US. It appears promising for obtaining an early diagnosis, tracking outcomes, and monitoring treatment in patients with tendon injury. However, it is not yet well standardized, and technical issues remain.


Magnetic Resonance Imaging

Currently, magnetic resonance imaging (MRI) is probably the imaging study of choice when there is any doubt about the diagnosis. MRI can clearly depict the laminated structure of the quadriceps tendon. Complete ruptures show transection of all of the layers of the tendon. Incomplete ruptures show discontinuities of individual layers, with the remaining layers intact (see the image below).

Magnetic resonance imaging (MRI) scans of complete Magnetic resonance imaging (MRI) scans of complete and incomplete quadriceps tendon ruptures. Reproduced with permission from Zeiss J, Saddemi SR, Ebraheim NA. MR imaging of the quadriceps tendon: normal layered configuration and its importance in cases of tendon rupture. AJR Am J Roentgenol. Nov 1992;159(5):1031-4.

An MRI study by Falkowski et al found that quadriceps femoris tendon tears most often involve the rectus femoris or vastus lateralis/medialis layers, usually in proximity to the patella; bony avulsion of the patella is correlated with a more extensive tear of the superficial and middle layers of the tendon. [49]


Histologic Findings

Histologic study is usually not included in the preoperative workup. For histologic details, see Pathophysiology.