Quadriceps tendon tears are uncommon, and usually coexist with prior degenerative changes in the knee. Ruptures of this kind tend to occur unilaterally. A tear can be partial or complete; a complete tendon tear of this kind is a debilitating injury requiring surgery.
X-ray of a quadriceps rupture
MRI showing chronic quadriceps rupture
Link to procedure here.
Dr. John Theodoropoulos