Most common causes: runner's knee, IT band syndrome.

Knee pain is one of the most common sports injuries, affecting both professional athletes and amateurs. Most common causes: runner's knee, IT band syndrome.
This injury is especially common among athletes who train intensively without proper warm-up or rest. By noticing symptoms in time and starting treatment, chronic problems can be avoided in many cases.
Knee pain can originate from inside the joint (cartilage, menisci) or from surrounding structures. A common variant is pain at the front of the knee or around the patella, worsened by a sudden increase in load and weak thigh and gluteal muscles. It is important to note when it hurts — when squatting, going down stairs, or after sitting for a long time — because this helps to understand the cause.