ruptured patellar tendon

My mother had a knee repacement a year ago. Even after rehab she complained the knee felt weak, like it was going to give out. She has fallen three times. She recently had a replacement on the other knee and noticed the difference in recovery right away that there seemed to be a weakness still in the knee she had done a year ago. The doctor often would answer my mothers concerns by telling her the knee was fine it was just in her head, and she just needed to continue to strengthen her leg with further excersise. This past week a doctor at the facility she was going for therapy at said it looked like she had a ruptured patellar tendon on the knee that was done a year ago and that she would need surgery to fix it. She had an x-ray done during the week but i believe that was to make sure the new replacement was doing fine. There was no MRI done on the leg that was diagnosed to have the rupture and she's scheduled for surgery on monday. My question is: can a patellar tendon rupture be diagnosed by just looking at the leg or should there be more tests done to confirm this to be the problem?, and also my mother has not complained of any pain at all, She just describes it as a weakness in the leg and a feeling that she will fall, and in fact has fallen. When someone describes a ruptured patellar tendon it always seems to accompany a great deal of pain.

[Dr Vinod]

After knee replacement surgery the most important thing is the patient should not fall. the 3 falls she had; might be she injured something? May be Quadriceps. Patella is a bone inside the tendon of Quadriceps and she has to be diagnosed with the reason of the failure of surgery she had for knee replacement an year ago.
She has to be properly diagnosed of the problem, all parameters explained to your mom before she undergoes repair. Take care!

[JACKOFHEARTS123]

Thank you for taking the time to respond to my problem/concerns. I will contact the doctor to see if i can learn more about the injury.