View source for Acute knee injury

==Background==
{{Knee ligaments}}
*Knee injuries are among the most common musculoskeletal complaints in the ED
*Mechanism of injury guides the differential (valgus stress, hyperextension, twisting, direct impact)

==Clinical Features==
*Acute pain, swelling, inability to bear weight
*Immediate large effusion (<2 hours) suggests hemarthrosis → ACL tear, fracture, or peripheral meniscal tear
*Locked knee (inability to fully extend) → meniscal tear with displaced fragment
*Giving way/instability → ligamentous injury
*Patellar apprehension → patellar subluxation/dislocation

===Key Exam Maneuvers===
*Lachman test: Most sensitive for ACL tear (anterior tibial translation at 20-30° flexion)
*Posterior drawer: PCL integrity
*Valgus stress (30°): MCL integrity
*Varus stress (30°): LCL integrity
*McMurray test: Meniscal tear (joint line tenderness is more sensitive)

==Differential Diagnosis==
{{Knee DDX}}

==Evaluation==
{{Ottawa knee rules}}
{{Knee x-rays}}
*X-ray if Ottawa knee rules positive
**Lipohemarthrosis on lateral view (fat-fluid level in suprapatellar bursa) = occult fracture until proven otherwise
*MRI for suspected ligamentous or meniscal injury (usually outpatient)
*Aspiration if large tense effusion causing significant pain: send cell count, culture, crystals

==Management==
*If x-rays positive (fracture): treat underlying condition, splint, orthopedic consult
*If x-rays negative or not indicated per [[Ottawa knee rules]]:
**Perform full ligamentous exam
**Stable exam: RICE (rest, ice, compression, elevation), crutches if unable to bear weight, NSAIDs
**Unstable exam or unable to evaluate (pain/swelling): knee immobilizer + RICE, weight-bearing as tolerated with crutches

==Disposition==
*Most acute knee injuries are managed as outpatient with orthopedics referral
*'''ED consult/admit:''' [[Knee dislocation]] (check vascular status — popliteal artery injury), open fractures, [[septic arthritis]]
*Urgent orthopedics follow-up (within 1 week) for suspected ACL/meniscal tears, locked knee

==See Also==
*[[Knee diagnoses]]
*[[Knee dislocation]]
*[[Patellar dislocation]]
*[[ACL tear]]

==References==
<references/>

[[Category:Orthopedics]]