Look, feel, move, then ligament and meniscal tests
Expansion
Look, standing then lying: varus or valgus alignment, quadriceps wasting (measure 20 cm above the tibial tuberosity), swelling, scars, fixed flexion, popliteal swelling from behind, and the gait.
Feel: temperature, the joint lines with the knee flexed to 90 degrees, the patella, tibial tuberosity, collateral ligament origins, and the popliteal fossa.
Effusion
- Patellar tap for a moderate effusion: empty the suprapatellar pouch, then press the patella down onto the femur
- Bulge or sweep test for a small effusion: sweep fluid from the medial compartment, then from the lateral, and watch the medial dimple refill
- Cross-fluctuation for a large effusion
Move: flexion to about 135 degrees, extension to 0 with up to 10 degrees of hyperextension, and note crepitus and any extensor lag on active straight leg raise, which indicates extensor mechanism disruption.
Special tests
| Test | Structure |
|---|---|
| Anterior drawer, knee at 90 degrees | Anterior cruciate |
| Lachman, knee at 20 to 30 degrees | Anterior cruciate, more sensitive |
| Posterior drawer and posterior sag | Posterior cruciate |
| Valgus stress at 0 and 30 degrees | Medial collateral |
| Varus stress at 0 and 30 degrees | Lateral collateral |
| McMurray | Meniscus |
| Patellar apprehension | Patellar instability |
Laxity at 30 degrees only indicates isolated collateral injury; laxity in full extension implies a cruciate injury as well, and is a more serious knee.