A knee injury refers to any damage or harm caused to the knee joint, which is a complex structure made up of bones, ligaments, tendons and cartilage. Such injuries can result from various causes such as falls, accidents, contact sports, overuse or sudden twists. Common types of knee injuries include sprains (where ligaments are stretched or torn), strains (where muscles or tendons are damaged) and dislocations (where the bones in the joint become misaligned). Symptoms may vary depending on the severity of the injury, but can include pain, swelling, stiffness, bruising, difficulty walking or moving the knee. Treatment for a knee injury typically involves rest, ice, compression and elevation (RICE) as well as physical therapy to help restore strength and mobility. In some cases, surgery may be required if the damage is severe enough.