By: Juliana Jaramillo, MD PGY2
Case: 24 year-old female presents with right knee pain after slipping on ice. Her right leg got caught and twisted, and she felt as if something came out of place. She is unable to extend at the knee.
Upon evaluation of patient you see this:
The patella lies in the groove between the two femoral condyles and is maintained in its location by various structures including: Vastus medialis, medial retinaculum, medial/lateral patellofemoral ligaments, and patellotibial ligaments. Dislocations tend to be the result of trauma or chronic patellofemoral anatomic abnormalities. The majority of the cases are seen in the young, particularly in 10-17 year-olds. The most common presentation for acute, primary patellar dislocations is in the setting of trauma typically after a sudden twisting motion in the opposite direction of the foot. Most frequently, the patella will be displaced laterally, however have been seen to dislocate either medially, superiorly, horizontally, or even intercondylar.
The patient will frequently report the sensation of something coming out of place or he/she will note a deformity. Commonly, upon arrival, the patella may be noted to have reduced spontaneously. If not, then manual reduction should be performed. Typically this is done by slowly and gently extending the lower leg while holding the patella in place until the leg is fully extended. Medial force is not always required.
Radiographs should be obtained following reduction to ensure that there is no fracture. Fractures associated with this injury may include avulsion fractures of the superior aspect of the patella and osteochondral fractures of the lateral femoral condyle or posteromedial facet of the patella. Edema and hemarthrosis are frequently seen; hemarthrosis, specifically, should raise suspicion for an osteochondral fracture. Careful evaluation of the integrity of the knee ligaments should be performed. Patella dislocations predispose the patient to complications such as arthritis and recurrent dislocations or subluxations. According to existing literature, aside from recurrence, acute patellar dislocation can lead to significant disability and discomfort due to recurrent pain, symptomatic joint laxity, and limitations with strenuous activities. Management of primary patellar dislocations can be controversial but is typically conservative with reduction followed by immobilization for up to 6 weeks. Prompt orthopedic follow-up in 1-3 days is recommended. There is some debate regarding early surgical intervention in attempt to reduce morbidity and recurrence rates, but data is limited.
- Arendt, Elizabeth A; Fithian, Donald C; Cohen, Emile. Current concepts of lateral patella dislocation. Clinical Sports Med. 2002. 499-519
- Jain, Neel P; Khan, Najeeb; Fithian, Donald C. A Treatment Algorithm for Primary Patellar Dislocations. Sports Health. 2011, March. 3(2): 170-174
- Simon, Robert R. et al. Emergency Orthopedics. 6th Edition. McGraw-Hill Companies. 2011.
Edited by Dr. deSouza