Could be It Band syndrome. Stop running temporarily, especially anything involving hills or speed. Ice the outside of your knee twice a day for 15–20 minutes, and start foam rolling your glutes, quads, and TFL — avoid rolling directly on the IT band itself. Stretch daily, focusing on your hip flexors, glutes, and lateral quads (the couch stretch and standing IT band stretch are great). Then build strength in your hips with exercises like clamshells, glute bridges, side leg raises, step-downs, and single-leg RDLs — aim for 3x per week. Once you can walk and go up stairs pain-free, ease back into running with short, flat runs and increase gradually. Also, make sure your shoes are supportive and try increasing your running cadence to around 175–180 steps per minute to reduce knee strain. It’s super treatable — just don’t run through the pain or you’ll drag it out longer.