Minor Effusion Test

The Minor Effusion Test (also commonly called the Bulge Test, Sweep Test, or Stroke Test) is a physical examination used to detect small amounts of intra-articular fluid (effusion) in the knee joint. It is designed to identify subtle knee joint swelling before it is grossly apparent.

How the Test is Performed

• Client position: Supine (lying flat) and relaxed, with the knee fully extended.

• The examiner uses the palm or edge of the hand to gently “milk” or “sweep” the medial aspect of the knee up toward the suprapatellar pouch to move any fluid away from the inside of the joint (repeat 2–3 times).

• Next, the examiner sweeps down the lateral aspect of the knee; while watching the medial joint line, a bulge or wave of fluid may appear if effusion is present.

• A positive test: Visible or palpable bulge of fluid on the medial side after sweeping the lateral side, graded from trace (“small wave”) up to 3+ (large persistent bulge).

• This is most specific for smaller effusions (as little as 2–5 mL of joint fluid).

Clinical Significance

• The bulge or minor effusion test is sensitive for small joint effusions, such as those seen early after trauma, in osteoarthritis, inflammatory arthritis, or less severe injuries.

• Helps differentiate true joint (intracapsular) swelling from extra-articular swelling (bursa, fat pads).

• Serial assessment and grading of minor effusions is useful for monitoring recovery after injury or surgery and for guiding progression or regression of exercise programs.

Assessment

• Use in clients with subtle or mild knee swelling, pain, or after low/moderate trauma or arthritic flare-ups.

• Document presence and grade of effusion, location (medial or lateral), and change after intervention or activity.

• Grading:

  • 0 – no wave

  • trace – small wave

  • 1+ – larger wave

  • 2+ – effusion returns spontaneously

  • 3+ – unable to move effusion out at all

Treatment

• If positive:

  • Avoid deep massage, compressive techniques, or mobilization over a swollen knee; focus on gentle lymphatic drainage techniques, pain relief, and supportive care until inflammation resolves.

  • Educate about rest, elevation, and anti-inflammatory strategies as indicated; avoid heat or excessive loading in the acute phase.

  • Modify activities and rehabilitation if effusion increases or persists—do not progress exercise when there is a persistent or increasing effusion.

Safety and Referral

• Refer to a physician/orthopedic specialist if minor effusion is associated with new trauma, functional limitation, warmth/redness, or does not improve with conservative care.

• Use the test serially to track response to therapy and determine when it is safe to increase activity levels again