A 49 yo M presents to the ED c/o L knee pain after a slip and fall in the bathroom. He heard a "pop" and since has had progressive knee swelling. He cannot bear weight. On exam, you note L knee swelling and he is unable to extend the L knee. XR is obtained and shown below. What's the diagnosis? (scroll down for answer.

Answer: Patella fracture with disruption of knee extensor mechanism
-Diagnosis:
-direct trauma to knee/patella
-knee effusion on exam
-if displaced, patella may be palpable as multiple pieces
-confirmation w/ XR
-check function of knee extensor w/ straight leg raise

-Treatment:
-pain control
-displacement > 3mm or disruption of knee extension: knee immobilizer, non-weight bearing--> outpatient followup for surgical management
-nondisplaced with knee extension intact: as above, but likely nonsurgical (4-6 weeks in immobilizer w progressive weight bearing)

References:
Bengtzen R. Knee Injuries. In: Tintinalli JE, Ma O, Yealy DM, Meckler GD, Stapczynski J, Cline DM, Thomas SH. eds. Tintinalli's Emergency Medicine: A Comprehensive Study Guide, 9e. McGraw Hill; 2020