Pearls

If extensor mechanism function is intact management is non-operative, weight bearing as tolerated.

Evaluating extensor mechanism:

1. Check function by asking patient to extend at the knee. Ensure there is a smooth arc motion without extension lag. Extension lag is a delay in the final 15-20° of extension which indicates accessory muscle use. The presence of extension lag indicates loss of normal extensor function.
2. If struggling to overcome gravity, patient can be turned on their side to evaluate extensor mechanism function.