Do most people need crutches for tendonitis in the knee?

Crutches - exception. Crutches are the exception rather than the rule. But if the problem is severe and persistent then crutches could unload the tendons and allow them to heal. You should discuss crutches with you physician and/or therapist.S.
No. For tendinitis the usual treatment is resting the inflamed muscle, ice, anti-inflammatories, stretching. A physical therapist can provide the proper direction and can add ultrasound, electrical stimulation, and iontophoresis. The doctor can inject the tendon with corticosteroids if the above is not providing timely or significant improvement.