Physical examination of the knee
A complete knee examination is always done for a knee complaint. Both of your knees will be checked, and the results for the injured knee will be compared to those of the healthy knee. Your doctor will also check that the nerves and blood vessels are intact.
Your doctor will:
- Inspect your knee visually for redness, swelling, deformity, or skin changes.
- Feel your knee (palpation) for warmth or coolness, swelling, tenderness, blood flow, and sensation.
- Test your knee's range of motion and listen for sounds. In a passive test, your doctor will move your leg and knee joint. In an active test, you will use your muscles to move your leg and knee joint. At the same time, your doctor will listen for popping, grinding, or clicking sounds.
- Check your
knee ligaments, which stabilize the knee. Tests
- The Valgus and Varus tests, which check the medial and lateral collateral ligaments. In these tests, while you lie on the examining table, your doctor places one hand on your knee joint and the other on your ankle and moves your leg side-to-side.
- The posterior drawer test, which checks the posterior cruciate ligament. In this test, you lie on the table with your knee bent at a 90-degree angle and your foot flat on the table. Your doctor will put his or her hands around your knee and push the top of your knee with the thumb.
- The Lachman test, which checks the anterior cruciate ligament (ACL). In this test, while you lie on the table, your doctor will slightly bend your knee and hold your thigh with one hand. With the other hand, he or she will hold the upper part of your calf and pull forward. The Lachman test diagnoses a complete ACL tear.
- A pivot shift test, which checks the ACL. In this test, the leg is extended and your doctor holds your calf with one hand while twisting the knee and pushing toward the body. It is often done just before a knee arthroscopy and after anesthesia has completely relaxed the muscles.
A McMurray test may be done if your doctor suspects a problem with the menisci based on your medical history and the above examinations. In this test, while you lie on the table, your doctor holds your knee and the bottom of your foot. He or she then pushes your leg up (bending your knee) while turning the leg and pressing on the knee. If there is pain and the sound or feeling of a click, the menisci may be damaged.
Arthrometric testing of the knee may also be done. In this test, your doctor will use an instrument to measure the looseness of your knee. This test is especially useful in people whose pain or physical size makes a physical exam difficult. An arthrometer has two sensor pads and a pressure handle that allows your doctor to put force on the knee. The instrument is strapped on to your lower leg so that the sensor pads are placed on the knee cap and the small bump just below it (tibial tubercle). Your doctor then measures pressure by pulling or pushing on the pressure handle.
Your exam may also include other tests to assess the degree of the injury and to identify damage to other parts of the knee.
Why It Is Done
A complete physical exam of the knee is always done for a knee complaint, whether the complaint is from a recent or sudden (acute) injury or from long-lasting or recurrent (chronic) symptoms.
In general, in a normal knee exam:
- The knee has its natural strength.
- The knee is not tender when touched.
- Both knees look and move the same way.
- There are no signs of fluid in or around the knee joint.
- The knee and leg move normally when the ligaments are examined.
- There is no abnormal clicking, popping, or grinding when knee structures are moved or stressed.
- The toes are pink and warm, and there is no numbness in the lower leg or foot.
If any of these findings are not true—for example, the knee is tender—you may have a knee injury. But the results of a knee exam vary depending on whether the exam is for a sudden injury to the knee or for long-term symptoms and also depending on how long it has been since the injury occurred. An abnormal finding does not always mean that your knee is injured. Your doctor will use the results of the exam, plus your medical history, to make a diagnosis.
What To Think About
These tests provide the best information if there is little or no knee swelling, you are able to relax, and your doctor is able to move your knee and leg freely. If this is not the case, it may be difficult to accurately check your knee.
If your knee is red, hot, or very swollen, a knee joint aspiration (arthrocentesis) may be done, which involves removing fluid from the knee joint. This is done to:
- Help relieve pain and pressure, which may make the physical exam easier and make you more comfortable.
- Check joint fluid for possible infection or inflammation.
- See if there is blood in the joint fluid, which may indicate a tear in a ligament or cartilage.
- See if there are drops of fat, which may indicate a broken bone.
Local anesthetic may be injected after aspiration to reduce pain and make the exam easier.
If you are going to have arthroscopy, the knee may be examined in the operating room before the procedure, while you are under general or spinal anesthesia.