Management of Knee Swelling After Trauma

Initial Assessment and Imaging

The American College of Radiology recommends beginning with plain radiographs (anteroposterior and lateral views) as the initial imaging study, especially if the patient has focal tenderness, joint effusion, or inability to bear weight 1, 2, 3
Obtain knee radiographs immediately if any Ottawa knee rule criteria are present, including age >55 years, focal tenderness at the patella or fibular head, inability to bear weight for 4 steps immediately after injury, or inability to flex knee to 90 degrees 3
Order radiographs regardless of Ottawa criteria if gross deformity is present, palpable mass, altered mental status, neuropathy, or history suggesting increased fracture risk 1, 3, 4
Minimum radiographic views should include anteroposterior view, lateral view (with knee at 25-30 degrees flexion), and consider patellofemoral view if patellar injury is suspected 1, 3

Assess for vascular injury if significant trauma mechanism, and check for absent pulses, pallor, or neurological deficits, which require immediate CTA of the lower extremity 1, 2, 3
Vascular injury occurs in approximately 30% of posterior knee dislocations 1

If radiographs show fracture, proceed to orthopedic consultation for definitive management 1
Consider CT without contrast for better fracture characterization, particularly for tibial plateau fractures 2, 3
If radiographs are negative, the ability to bear weight is a positive prognostic sign, but does not rule out significant soft tissue injuries 3
Order MRI without IV contrast if significant joint effusion persists, inability to fully bear weight, mechanical symptoms, or joint instability on examination 3, 5
MRI without contrast is superior for evaluating meniscal tears, ligamentous injuries, bone marrow contusions, and occult fractures, as well as articular cartilage damage 5

For patients with negative radiographs and ability to bear weight, initiate conservative management, including pain and swelling control with NSAIDs, which help reduce swelling and pain and may decrease time to return to usual activities 4
Functional support with semirigid or lace-up ankle supports is recommended as functional treatment, and these devices decrease the risk of recurrent injury, especially in patients with a history of previous sprains 4
Maintain range of motion exercises and focus on quadriceps activation, and progress weight-bearing as tolerated 3, 4
Re-examination at 3-5 days post-injury is critical, as excessive swelling and pain can limit initial examination accuracy 4

Refer to orthopedics if joint instability on examination, inability to bear weight persisting beyond 5-7 days, mechanical symptoms, or MRI reveals significant ligamentous injury or complex meniscal tear 3, 4, 5

Do not assume negative radiographs rule out significant injury—occult fractures and soft tissue injuries are common 3
Avoid ordering MRI with IV contrast for routine meniscal or ligamentous injuries—it provides no additional diagnostic value over non-contrast MRI 5