Pain in the joints associated with activity or any external changes in the appearance of your joints are symptoms that should definitely be evaluated by an orthopedic surgeon
. There are many different types of problems--injuries to the tendons or ligaments, infections, fractures, even tumors--that can cause these kinds of symptoms and it is important to have a physician perform a more complete history and physical exam to distinguish between the possibilities. In particular, radiographic imaging such as X-rays or MRI
studies can also be very helpful in evaluating this kind of joint pain.
Overall, the symptoms you describe could be suspicious for a condition called Osgood-Schlatter syndrome. This is a condition that is commonly found in young athletes, especially men, and is caused by the tendon that helps keep the kneecap in place pulling away from the lower bone of the leg (the tibia). This causes pain and inflammation below the knee, and when new bone grows back it can cause a visible and painful "lump." This kind of pain is exacerbated by touching the area and is usually better with rest.
Treating Osgood-Schlatter usually involves anti-inflammatory medications, ice, and rest. However, it is important to be evaluated by an orthopedist to properly diagnose and manage the painful knee.