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
