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| IMAGE QUIZ ARCHIVE | ||||||
| Image Quiz | ||
| An Unusual Presentation of a Locked Knee (continued) |
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| Answer: Inferior intra-articular dislocation of the patella | ||
 Fig. 1 |  Fig. 2 | |
| Figs. 1 and 2: Inferior intra-articular dislocation of the patella without patellar rotation. | ||
| The patient underwent an operative procedure under general anesthesia. The patella reduced spontaneously when the knee was extended in preparation for surgery. Intraoperative exploration of the extensor mechanism did not reveal a discontinuity. Postoperatively, no form of immobilization was used, and active-assisted mobilization of the knee was begun on the first day. The patient was able to perform a straight leg raise on the second postoperative day, and she regained pre-injury range of movement of the knee within one week. | ||
| Discussion | ||
| Various predisposing factors have been described in association with patellar dislocation, including excessive femoral and/or tibial external rotation, imbalance between the vastus medialis and vastus lateralis muscles, dysplasia of the lateral femoral condyle, an abnormal Q angle, and generalized ligamentous laxity of the knee. The patella usually dislocates in a lateral direction but can also dislocate superiorly or inferiorly or rotate around its horizontal or vertical axis. When the superior pole of the patella becomes trapped in the intercondylar notch, the injury is defined as a central or intra-articular dislocation1,2. | ||
| Inferior dislocation is rare, particularly in elderly patients1,3,4-6. Most cases of inferior dislocation of the patella have been described in young patients. Approximately forty cases of inferior dislocation of the patella have been described in the world literature. Various treatment options have been described and include manipulation under sedation3, closed reduction under anesthesia4,5, and open reduction6-8. | ||
| Bankes and Eastwood3 classified inferior dislocation of the patella into two types according to the presence of patellar rotation (Type 1) and osteophytes (Type 2). Type 1 is seen in adolescents, usually in boys in their second decade, following a direct blow to the flexed knee. Closed reduction is usually possible, but the extensor mechanism may be disrupted and may require operative repair7,8. Type 2 is seen in elderly women and is associated with the presence of a marginal patellar osteophyte. The extensor mechanism has been found to be intact in reported cases of inferior dislocation in elderly patients (Table I). Therefore, we recommend nonoperative treatment of this injury unless there is clinical evidence of disruption of the extensor mechanism and the patella does not rotate in the horizontal plane. | ||
| Table I Status of the Extensor Mechanism After Inferior Dislocation of the Patella in Elderly Patients | ||||
| Study | Age of Patient (yr) | Gender | Procedures/Findings | Final clinical outcome/Time to full recovery |
| Bankes and Eastwood (2002) | 86 | F | Hyperflexion of the knee under sedation/Ultrasound imagery of the extensor mechanism showed no disruption | Good/One month |
| Nielsen et al. (1993) | 87 | F | Manipulation after intra-articular injection of local anesthesia/The patella re-dislocated and required open reduction. The extensor mechanism was intact | Good/One month |
| Hersch et al. (1999) | 75 | M | Manipulation under general anesthesia with use of a towel clip to reduce the patella/Magnetic resonance imaging of the extensor mechanism showed no disruption. The patient underwent total knee replacement after six weeks | Good/Patient was fully weight-bearing immediately after the operation |
| Desai et al. (1995) | 88 | F | Hyperflexion of the knee under general anesthesia/The extensor mechanism was explored surgically and showed no disruption | Good (complete recovery)/Time not stated |
| Joshi (1997) | 80 | F | Manipulation under general anesthesia/The extensor mechanism was clinically intact on examination. No tests or exploration was performed | Good (complete recovery/Time not stated |
| *The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated. | ||
| References | ||
1. Desai A, Allcock S, Hardy SK. Horizontal intra-articular dislocation of the patella in an 88-year-old woman. The Knee. 1995;2:233-4. |
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