Does bicycling aggravate runner's knee and patellar tendinitis?

It can: Inflammation of the patella due to overuse or repetitive motion. Overuse injuries respond best with rest, ice and nsaids. Therapy helps with decreasing swelling and pain as well as improving strength and range of motion. Recurring tendinitis could be occurring due to needing to improve running form or perhaps needing orthotics.

It can: Acutely you want to reduce your strain on the tendon. You need to stretch your quads and slowly return you activity level in a controlled fashion to allow your tendon to build up tolerance again to the activities you do. Constant straining and loading your patella tendon can be aggravating to it unless done in a controlled environment. Work with your doctor and physical therapist to improve.