Confirmation of an intact patellar tendon in superior dislocation of the patella using magnetic resonance imaging

Superior Patellar Dislocation Reduced by Intra-articular Injection: A Case Report and Review of Literature

CASE

A 53-year-old woman presented with a locked knee after an atraumatic hyperextension episode. Imaging showed an anterior tilt of the patella hinging over the superior trochlear margin, consistent with a superior patellar dislocation. The patella spontaneously reduced on an intra-articular injection with 15 mL of lidocaine in normal saline, after which she was able to actively range her knee.

CONCLUSION

Superior patellar dislocations are rare and usually result from a sudden forced contraction of the quadriceps, trapping the patella over superior trochlear osteophytes. Reduction is possible through an intra-articular local anesthetic injection, without manipulation of the patella.

[A rare cause of an acutely locked knee joint: superior patellar dislocation]

The case of a 56-year-old male patient with locking of the knee in extension without trauma is presented. Patient history, clinical examination and radiographs confirmed a superior dislocation of the patella. Closed reduction led to full weight bearing with free range of motion without further complaints. Knowledge of this uncommon cause of a locked knee joint leads to immediate treatment avoiding complex imaging modalities, such as computed tomography (CT) or magnetic resonance imaging (MRI). No further treatment was necessary in the majority of the cases published in the literature.

Superior dislocation of the patella: a pathognomonic finding and review of literature

A 59-year-old woman with a painful right knee that became locked in extension after a trivial trauma was seen at the emergency room. This was caused by unloaded hyperextension in bed. She was diagnosed with a superior dislocation of the patella. A closed reduction was performed, but a recurrent episode was seen within a week. An arthroscopy was performed, in which the causative osteophytes were removed. In the 12-month follow-up after treatment, no recurrence was seen. A superior dislocation of the patella is caused by patellofemoral osteophytes that interlock. This can cause a degenerative knee to become locked in extension. Beside interlocking osteophytes of the patella and the distal femur, the superior part of the patella is tilted away from the femur. This is caused by the pull of the patella tendon and the simultaneous relaxation of the quadriceps tendon. This is a pathognomonic finding on radiographs that, to the best of our knowledge, has been identified but not been appreciated as such in previous reports. As illustrated in this report, a superior dislocation of the patella can easily be recognized on physical examination and radiographic imaging alone when familiar with the specific abnormalities. This will reduce unnecessary diagnostic imaging studies and delay in treatment. This case report illustrates a recurrent case of superior dislocation of the patella. We summarize and evaluate previous reports, discuss trauma mechanisms, physical examination, classification, and treatment including recurrent cases. After reading this case report the reader will be able to diagnose a superior dislocation of the patella with near certainty on physical examination and radiographic imaging of the knee alone.

Superior Patellar Dislocation Misdiagnosed as Patellar Tendon Rupture: The Value of Ultrasonography

Superior dislocation of the patella with intact patellar tendon is a rare condition. Most cases in literatures were diagnosed by clinical examination and plain radiography; however there are many cases that were misdiagnosed as patellar tendon rupture. In this case, we demonstrate the use of ultrasound for diagnosis of superior dislocation of the patella in the emergency department. We also include a literature review of similar cases and discuss the advantages of different types of imaging for diagnosis in this condition.

Superior patellar dislocation: the value of clinical examination and radiological investigation

A 57-year-old obese woman with a history of osteoarthritis presented with an acutely painful left knee and an inability to bear weight following a twisting injury. The initial diagnosis in A&E was a ruptured patellar tendon. A more thorough clinical examination revealed a high-riding patellar with the knee hyper-extended and a patellar dimple, consistent with superior patellar dislocation. The diagnosis was confirmed with imaging and the patient successfully underwent closed reduction. She re-presented 2 months later with ipsilateral knee pain after climbing a step. The initial diagnosis was quadriceps tear and ultrasound confirmed a partial tear in proximal vastus medialis. She was discharged home with analgesia and splinting of the leg. Subsequent MRI demonstrated severe tricompartmental degenerative changes in the left knee, the tear in vastus medialis noted on ultrasound with disruption to the medial capsular structures in keeping with lateral subluxation of the knee.

Superior dislocation of the patella: a case report

Background

Superior dislocation of the patella is an uncommon condition that mainly occurs in knees with a high patella and medial femorotibial degenerative arthritis. There are no previous reports of this condition occurring in association with tibial valgus osteotomy. Case report: We report the case of a patient in whom vertical dislocation recurred twice at 4 months after tibial valgus osteotomy. To avert additional recurrence or new dislocations, the patient was treated surgically to remove the existing osteophytes. Conclusions: An arthroscopic approach was decided because of the lower associated morbidity and good results with this technique compared to open surgery.