Major Effusion Test – Ballottable Patella

Orthopedic Exam / Special Tests for Physical Therapy: KNEE

Major Effusion Test – Ballottable Patella Test:

Knee effusion or swelling of the knee (colloquially known as water on the knee) occurs when excess synovial fluid accumulates in or around the knee joint. There are many common causes for the swelling, including arthritis, injury to the ligaments or meniscus, or fluid collecting in the bursa, a condition known as prepatellar bursitis. 

Signs and Symptoms:

Signs and symptoms of water on the knee depend on the cause of excess synovial fluid build-up in the knee joint. These may include: 

  1. Pain – Osteoarthritis knee pain usually occurs while the joint is bearing weight, so the pain typically subsides with rest; some patients suffer severe pain, while others report no discomfort. Even if one knee is much larger than the other, pain is not guaranteed.
  2. Swelling – One knee may appear larger than the other. Puffiness around the bony parts of the knee appear prominent when compared with the other knee.
  3. Stiffness – When the knee joint contains excess fluid, it may become difficult or painful to bend or straighten. Fluid may also show under the knee when straightened. Icing may help to decrease swelling. Heat may help relax the muscles of the knee.
  4. Bruising – If an individual has injured his or her knee, he or she may note bruising on the front, sides or rear of the knee. Bearing weight on the knee joint may be impossible and the pain unbearable.


Causes of the swelling can include arthritis, injury to the ligaments of the knee, or an accident after which the body’s natural reaction is to surround the knee with a protective fluid. There could also be an underlying disease or condition. The type of fluid that accumulates around the knee depends on the underlying disease, condition or type of traumatic injury that caused the excess fluid. The swelling can, in most cases, be easily cured.

Underlying diseases may include: Knee osteoarthritis, Rheumatoid arthritis, Infection, Gout, Pseudogout,     Prepatellar bursitis (kneecap bursitis), Cysts, Tumours, Repetitive strain injury.

Major Knee Effusion Test – Ballottable Patella Test


  • Usually performed after an injury to assess for a major increase in the synovial fluid or blood within the knee joint capsule.

Video Demo Instructions, Procedure, Positive Test:

Major Knee Effusion Test – Ballottable Patella Test Video Demo (Procedure below)

Major Knee Joint Effusion Test – Ballottable Patella Test PROCEDURE:

• Client is supine, the affected knee is extended as much as possible ( with effusion, client may not be able to extend their knee fully)
• Therapist gently extends the knee further, then compresses the patella down on to the condyles then release

Major Effusion Test – Ballottable Patella Test POSITIVE SIGN:

  • Patella clicks onto the femur and then rebounds to the floating position. This could be caused by torn cruciate ligaments, meniscal tearing, or fracture and is considered a Medical Emergency. (Joint effusion within two hours of injury might be caused by blood in the joint, and joint effusion with synovial fluid usually develops 8 hours after injury.