3. Torn Meniscus
A meniscus is a piece of cartilage that prevents the bones of your knee joint from rubbing against each other. A forceful, twisting motion of the knee may result in rips to this cartilage. Symptoms may include a popping sound from the knee, pain when rotating the joint, and difficulty straightening your leg. Treatment for a torn meniscus ranges from rest for minor tears to surgery for more severe injuries. Meniscus tears can be prevented by keeping your leg muscles strong. Additionally, warming up before and cooling down after exercise can help decrease stress on the joint.
2. Torn Ligament
According to Johns Hopkins Medicine, there are four ligaments that aid in the mobility and function of the knee joint. They include the anterior cruciate ligament (ACL), the posterior cruciate ligament (PCL), the medial collateral ligament (MCL), and lateral collateral ligament (LCL). These tough bands of tissue surround the joint of your knee as they connect your thighbone to your shinbone. They lend support to your knee and allow it to move. If any of these ligaments become damaged through an injury, they can cause pain and difficulty in bending or straightening your knee.
In some cases, a tumor may cause knee pain. Cysts occur when cells begin rapidly and chaotically dividing. Most tumors are benign or non-cancerous. Osteosarcoma is a rare form of bone cancer that may develop in the knee. This tumor most frequently affects children and young adults. Physicians use a variety of tests to diagnose the cause of a tumor and determine the course of treatment. These tests may include a physical exam, imaging, bloodwork, and biopsies.