Pain that is more pronounced when the knee joint is suddenly bent may be due to meniscal injury of the knee joint or free body entrapment of the knee joint. Watch for other symptoms, such as popping or compression, and use the orthopedic surgeon’s examination to make a preliminary determination. If a free body of the knee is considered, an x-ray of the knee joint can be completed. If the knee is considered to be a meniscus injury, an MRI of the knee joint should be done to determine the condition. If the meniscus injury is mild, you can rest more and avoid prolonged walking and excessive knee flexion for a while to help you recover. For more serious meniscus injuries or obvious free bodies, conservative treatment is generally not effective and requires arthroscopic removal of the free body or repair of the meniscus.