These symptoms are likely due to inflammation of your joint. Inflammation is commonly due to osteoarthritis but can also be due to diseases like rheumatoid arthritis or gout. You should see a doctor immediately if you're also having fevers, chills, or other flu-like symptoms as this could be a sign of an infection that needs to be treated.
While the list below can be considered as a guide to educate yourself about these conditions, this is not a substitute for a diagnosis from a health care provider. There are many other medical conditions that also can be associated with your symptoms and signs. Here are a number of those from MedicineNet:
Osteoarthritis is a type of arthritis caused by inflammation, breakdown, and eventual loss of cartilage in the joints. Also known as degenerative arthritis, osteoarthritis can be caused by aging, heredity, and injury from trauma or disease.
Cellulitis is an acute spreading bacterial infection below the surface of the skin characterized by redness, warmth, inflammation, and pain. The most common cause of cellulitis is the bacteria staph (Staphylococcus aureus).
Abscessed Tooth Guide
An abscessed tooth is an infection within a tooth that has spread to the root. Symptoms of an abscessed tooth may include pain, swelling, tenderness, redness, and the presence of a pus-filled lesion on the gum. A dental professional diagnoses an abscessed tooth and dental X-rays may be required. An abscessed tooth is treated with a root canal.
Knee Injury and Meniscus Tears
Knee injuries, especially meniscus tears, are common in contact sports. Symptoms and signs of a torn meniscus include knee pain, swelling, a popping sound, and difficulty bending the leg. Treatment may involve resting, icing, compressing, and elevating the knee, in addition to wearing a knee brace, taking anti-inflammatory medications, and stretching the knee.
At MedicineNet, we believe it is important to take charge of your health through measures such as a living healthy lifestyle, practicing preventative medicine, following a nutrition plan, and getting regular exercise. Understanding your symptoms and signs and educating yourself about health conditions are also a part of living your healthiest life. The links above will provide you with more detailed information on these medical conditions to help you inform yourself about the causes and available treatments for these conditions.