Patellar tap

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Patellar tap is a clinical test used to assess the presence of a knee effusion, which is an accumulation of fluid in or around the knee joint. This test is also known as the ballottement test or ballotable patella test.

Procedure

The patellar tap test is performed with the patient lying supine and the knee extended or slightly flexed. The examiner uses one hand to compress the suprapatellar pouch, which is located above the patella, to push any fluid in the knee joint downwards. With the other hand, the examiner gently taps the patella. If there is a significant amount of fluid in the knee joint, the patella will be felt to "float" or "bounce" back, indicating a positive test.

Clinical Significance

A positive patellar tap test suggests the presence of a knee effusion, which can be caused by various conditions such as arthritis, trauma, infection, or other inflammatory processes. It is an important diagnostic tool in the evaluation of knee pain and swelling.

Related Tests

Other tests that can be used to assess knee effusion include the bulge sign and the fluid displacement test. These tests, along with the patellar tap, help in the clinical assessment of knee joint conditions.

Conditions Associated with Knee Effusion

- Osteoarthritis - Rheumatoid arthritis - Gout - Pseudogout - Septic arthritis - Meniscal tear - Ligament injury

See Also

- Knee examination - Joint effusion - Synovial fluid - Arthrocentesis