Diagnosis

During the physical exam, your doctor might press on your knee to feel for injury, looseness or fluid in the joint from bleeding. He or she may move your knee, leg or foot in different directions and ask you to stand and walk. Your doctor will compare your injured leg with the healthy one to look for any sagging or abnormal movement in the knee or shinbone.

In some cases, your doctor may suggest one or more of the following imaging tests:

• X-ray. While an X-ray can't detect ligament damage, it can reveal bone fractures. People with posterior cruciate ligament injuries sometimes have breaks in which a small chunk of bone, attached to the ligament, pulls away from the main bone (avulsion fracture).
• MRI scan. This painless procedure uses radio waves and a strong magnetic field to create computer images of the soft tissues of your body. An MRI scan can clearly show a posterior cruciate ligament tear and determine if other knee ligaments or cartilage also are injured.
• Arthroscopy. If it's unclear how extensive your knee injury is, your doctor might use a surgical technique called arthroscopy to look inside your knee joint. A tiny video camera is inserted into your knee joint through a small incision. The doctor views images of the inside of the joint on a computer monitor or TV screen.