Examination of the Knee

Determining the cause of knee pain relies on a proper examination of the knee joint. Learn about how your healthcare provider can examine your knee to determine the source of your knee pain, and what tests can be performed to make the diagnosis.

Knee Swelling

Many people know if their knee is swollen—they can see or feel the swelling without any difficulty. However, not everyone knows there is excess fluid in the knee joint. Your healthcare provider may compress the joint to feel for excess fluid.

Fluid in the knee can often be visible above the kneecap and can be compressed in this area. Fluid is also often detected in the back of the knee, which if collected into a pocket of fluid is often referred to as a Baker's cyst.

Knee Arthritis

Knee arthritis can be detected by looking for several characteristic examination findings:

• Crepitus: Crepitus is the sensation that is felt when rough cartilage or exposed bone is rubbing as the knee is bent. The examiner will feel (and may hear) this grinding as the knee is bent back and forth.
• Deformity: As the knee cartilage is worn away, the knees may become progressively knock-kneed or bow-legged.
• Limited motion: The range of motion of the knee typically becomes limited if arthritis, bone spurs, and swelling prevent normal mobility.

Torn Meniscus

Tests used to determine if there is a meniscus tear include:

• Joint line tenderness: Joint line tenderness is a very non-specific test for a meniscus tear. The area of the meniscus is felt, and a positive test is considered when there is pain in this area.
• McMurray's test: McMurray's test is performed with the patient lying flat on his back and the examiner bending the knee. A click can be felt over the meniscus tear as the knee is brought from full flexion to full extension.
• Ege's test: Ege's test is performed with the patient squatting, a click is heard/felt over the area of the meniscus tear.

ACL Tear

These tests may be done for a suspected anterior cruciate ligament (ACL) tear:

• Lachman test: The Lachman test is one of the best tests to diagnose an ACL tear. With the knee slightly bent, the examiner stabilizes the thigh while pulling the shin forward. A torn ACL allows the shin to shift too far forward.
• Anterior drawer test: This test is also performed with the patient lying flat on his back. The knee is bent 90 degrees and the shin is pulled forward to check the stability of the ACL.
• Pivot shift test: The pivot shift test can be a difficult maneuver to perform on a patient, especially if they are having discomfort and not able to relax the knee. This test places stress on the knee joint that assesses the rotational stability of the ACL.

Other Ligament Injuries

For supected injury to other ligaments, including the posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL), these tests may be done:

• Posterior drawer test: The posterior drawer is performed similarly to the anterior drawer test. This test detects injury to the posterior cruciate ligament (PCL). By pushing the shin backward, the function of the PCL is tested.
• Collateral ligament stability: Side-to-side stability of the knee detects problems of the MCL and LCL. With the patient lying flat, and the knee held slightly bent, the shin is shifted to each side. Damage to the LCL or MCL will allow the knee to "open up" excessively, a problem called varus (LCL) or valgus (MCL) instability.

Kneecap Problems

Tests for problems with the kneecap include:

• Patellar grind: The patient lies supine with the leg extended. The examiner reproduces the patient's knee pain by pushing the kneecap down and asking the patient to flex the thigh muscles. Damaged cartilage can cause a grinding sensation called crepitus.
• Patellar tenderness: The examiner can slightly lift up the kneecap and place direct pressure on parts of the undersurface of the kneecap. By doing so, the examiner is looking for regions of sensitivity or pain.
• Patellar apprehension: This is a sign of an unstable kneecap. While the examiner places pressure on the kneecap in a certain direction, the patient may complain of the sensation that the kneecap is going to "pop out" of its groove.