1) Knee Arthritis - Arthritis is among the most common causes of knee pain, and there are many treatments available.
2) Ligament Injuries - Ligament injuries commonly occur during athletic activities and can cause discomfort and instability.
- Anterior Cruciate Ligament (ACL) Injury
- Posterior Cruciate Ligament (PCL) Injury
- Medial Collateral Ligament (MCL) Injury
- Lateral Collateral Ligament (LCL) Injury
4) Osteochondritis Dissecans - Osteochondritis dissecans (OCD) is another condition seen in adolescents due to the growth of the bone around the joint.
5) Gout - Gout is an uncommon cause of knee pain. However, in patients who have a diagnosis of gout, it must be considered as a cause for new onset knee pain.
6) Patellar Tendonitis -Tendonitis around the joint is most commonly of the patellar tendon, the large tendon over the front of the knee.
7) Chondromalacia Patella - Chondromalacia causes knee pain under the kneecap and is due to softening of the cartilage. It is most common in younger patients (15-35 years old).
8) Dislocating Kneecap - A dislocating kneecap causes acute symptoms during the dislocation, but can also lead to chronic knee pain.
9) Baker's Cyst - A Baker's cyst is swelling in the back of the joint, and is usually a sign of another underlying problem such as a meniscus tear.
10) Bursitis - The most common bursa affected around the joint is just above the kneecap. This is most common in people who kneel for work, such as gardeners or carpetlayers.
11) Plica Syndrome - Plica syndrome is an uncommon cause of knee pain, and can be difficult to diagnose. The diagnosis is usually made at the time of arthroscopy.
12) Osgood-Schlatter Disease - Osgood-Schlatter disease is a condition seen in adolescents and is due to irritation of the growth plate just at the front of the joint.
Read more: http://orthopedics.about.com/cs/kneeinjuries/a/kneepain.htm