Written by: Victoria Adomshick, MD (NUEM ‘27) Edited by: Jackie Zewe, MD (NUEM ‘26)
Expert Commentary by: Matt Levine, MD
Patellar dislocation = displacement of the patella from trochlear groove
Types of dislocations & mechanism
Lateral (most common): internal rotatory force is applied to a flexed knee in valgus
Spinning in gymnastics, swinging a baseball, quick lateral changes when running
Superior (rare): hyperextension of the knee or blow to the knee with the leg in extension
Medial (rare): usually post op complication of lateral retinacular release procedure
Evaluation
History: knee giving away followed by severe pain, may have a pop sensation
Exam: knee held in 20-30 degrees of flexion and patella is visibly laterally displaced
Clinical diagnosis, imaging not necessary before reduction
Reduction
Pain management: fent
Procedural sedation may be necessary in children (see ED blog on procedural sedation https://www.nuemblog.com/blog/procedural-sedation)
Steps
Supine position w/ hips flexed
Slowly apply gradual medial pressure to lateral aspect of dislocated patella
Simultaneously slowly extend the knee until it reduces (patella is back in the tibiofemoral tract w/ normal flexion and extension of the knee)
Post reduction care
Radiographs: AP, lateral and patella to assess for fracture or avulsion.
40% of patients have associated fractures, typically located in the lateral femoral condyle or patella
Assess for signs of ligamentous injury
Place in knee immobilizer
NSAIDS, RICE
Follow up with PCP, ortho or sports med in 2-3 days to start rehab that is aimed at regaining quad strength to protect against subsequent dislocations
Athletes can return to play in 4-6 weeks
Risk of recurrence is high in patients <16 years old
Expert Commentary
Kudos to Dr. Adomshick for her handy high yield tool for managing patella dislocations.
The classic presentation would be a young female who sustains the injury doing a pivoting maneuver such as dancing or gymnastics. Many have had previous patella dislocations. The diagnosis should be obvious, a “doorway diagnosis”. Reduction can occur almost immediately. Many patients will be anxious and apprehensive of any manipulation and require pain medication. For calm and cooperative patients, reduction can proceed without medication since the procedure is so brief, avoiding the need for IV placement. The maneuver as described above should be performed smoothly and swiftly in one motion that should only take a few seconds.
Postreduction x rays are frequently negative but may show avulsion or osteochondral fractures on the medial aspect of patella (from ligamentous avulsion when the patella dislocates laterally) in up to 40% of cases, particularly in children. Physical therapy is important for quad strengthening to prevent recurrent dislocations.
An interesting scenario is when patients present with no dislocation saying that their “knee was dislocated” but then it reduced. The provider then must determine if the patient actually had a patella dislocation versus a true knee dislocation (a can’t miss limb threatening emergency!). After a reduced patella dislocation, patients will have apprehension if the examiner grasps the patella and starts to move it laterally (a positive “apprehension sign”). Medial patella avulsion fragments on x rays are also clues that the patient had sustained a patella dislocation. However, suspect that the patient actually had a true knee dislocation (and initiate the appropriate workup) if any of the following are present:
· Multidirectional (varus/valgus) instability
· Any instability with the knee in full extension
· Recurvatum (the knee extends beyond normal when passively elevated, a sign of PCL disruption)
· Uncontained hemarthrosis (suggests joint capsule rupture)
For a nice clinical photo and more information on patella dislocations, check out this case in our Orthopedics Teaching File:
https://www.ortho-teaching.feinberg.northwestern.edu/cases/leg-knee/case6/index.html
Matthew Levine, MD
Associate Professor
Department of Emergency Medicine
Northwestern Memorial Hospital
How To Cite This Post:
[Peer-Reviewed, Web Publication] Adomshick, V. Zewe, J. (2025, Sept 19). Patellar Dislocation. [NUEM Blog. Expert Commentary by Levine, M]. Retrieved from http://www.nuemblog.com/blog/patellar-dislocation
