complete quadriceps tendon rupture is a disabling injury , and prompt diagnosis and expeditious operative repair is required to obtain an optimal result .
we present a case of a complete quadriceps tendon tear in an uncooperative patient using point - of - care bedside ultrasound .
a 38-year - old man presented to the emergency department ( ed ) complaining of pain in his left knee and inability to ambulate after being tackled to the ground .
he stated that he had been drinking alcohol that day and got into a physical altercation that ended when police tackled him to the ground .
his past medical history consisted of schizophrenia , for which he was compliant with his medications .
the vital signs were all within normal limits , and the glasgow coma scale ( gcs ) was 15 .
his left knee demonstrated a large effusion with ecchymosis over the anterior , superior portion of his knee .
the patient was resistant to allow both active and passive range of motion of the knee , and refused assessment for ligamentous instability .
standard 3-view radiography of the knee was performed , which did not reveal any foreign bodies , fracture or subluxation .
given their diagnostic uncertainty , the authors performed a bedside ultrasound of the knee using a 13 - 6 mhz linear transducer ( sono - site m - turbo , bothell , wa ) .
ultrasound examination demonstrated an anechoic area at the distal end of the quadriceps tendon at its attachment to the superior pole of the patella , suggestive of a quadriceps tendon rupture [ figure 1 ] .
a comparison view of the right knee revealed no such abnormality [ figure 2 ] .
a sagittal image of the affected left knee demonstrates the ruptured quadriceps tendon ( t ) attached to the superior pole of the patella ( p ) .
note the loss of linear fibers of the tendon , which is filled in by an effusion ( * ) anterior to the distal femur ( f ) a sagittal image of the unaffected ( normal ) right knee clearly demonstrates the linear fibers of the quadriceps tendon ( t ) attached to the superior pole of the patella ( p ) and anterior to the distal femur ( f ) after the diagnosis was made , the patient was placed in a knee immobilizer ; the leg was elevated ; ice and analgesia were given ; and the orthopedic surgeons were notified .
the patient was admitted to the orthopedic service and underwent operative repair of a complete quadriceps tendon rupture the following day .
qtr is more common in the elderly , and often related to a slip or fall ; as opposed to a patella tendon rupture , which is often a sports - related injury in younger patients .
qtr is either traumatic ; idiopathic ; or due to a variety of systemic diseases , including gout , rheumatoid arthritis , lupus erythematosus , chronic renal failure , obesity , infections , diabetes mellitus , hyperparathyroidism ; or due to multiple steroid injections .
complete tears can often be diagnosed clinically ; loss of active leg extension , a palpable suprapatellar depression , and knee pain are common findings .
partial tendon tears may be more difficult to detect since some degree of function is maintained .
misdiagnosis is common , ranging between 10% and 50% , because the physical examination is often limited by pain and swelling .
ultrasound ( us ) and magnetic resonance imaging ( mri ) are more suitable imaging modalities because they allow for more detailed examination of the soft tissues .
mri is highly sensitive and specific for qtr and therefore the imaging study of choice .
ultrasound can differentiate between complete and partial tears , as well as demarcate the location of the tear .
when visualizing the quadriceps tendon on us , one usually sees a 6- to 11-mm thick structure with linear , parallel echoes running across its length representing the convergence of 4 muscle tendons : the rectus femoris , vastus medialis , vastus intermedius and vastus lateralis .
these tendons form 3 laminae : rectus femoris forms the superficial lamina ; vastus medialis and lateralis form the middle lamina ; and the vastus intermedius forms the deep lamina .
partial tears may affect single or multiple layers , while a complete tear represents rupture of all 3 layers .
in complete tears , a hypoechoic or anechoic area between the tendon fibers is usually seen , and is usually representative of a hematoma .
partial tears may display a focal hypoechoic defect in the tendon . if the patients can not flex their knee , gentle traction on the patella may lead to better visualization of the tendon defect .
ultrasound is an operator - dependent imaging modality , and tendon sonography can be technically challenging
. one must be aware that tendons on us display anisotropy , and therefore the probe should be kept perpendicular to the tendon to obtain the best resolution and to avoid false - positive results .
in conclusion , ultrasound is an imaging modality that should not be overlooked by an emergency physician when examining a patient with a painful , swollen knee .
 a 38-year - old intoxicated man presented to the emergency department with a painful , swollen left knee and inability to ambulate after being tackled to the ground . 
 the patient was uncooperative , and physical examination of the lower extremities was limited by his intoxication . 
 radiographic examination of the knee was unremarkable . 
 ultrasound of the knee revealed a quadriceps tendon rupture . 
 the sonographic features of quadriceps tendon rupture are described , as is the role ultrasound plays in the assessment of a swollen , painful knee . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSIONS