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Year : 2020  |  Volume : 17  |  Issue : 2  |  Page : 77-78

Superior dislocation of the patella: A rare cause for locked knee in extension

Department of Orthopedics, Apollo-Adlux Hospital, Angamaly, Kerala, India

Date of Submission21-Nov-2020
Date of Acceptance13-Dec-2021
Date of Web Publication08-Mar-2021

Correspondence Address:
K R Renjith
Department of Orthopedics, Apollo-Adlux Hospital, Near Adlux Convention Center, Cable Junction, Ernakulam District, National Highway 47, Karukutty, Angamaly - 683 576, Kerala
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/joasis.joasis_13_20

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Superior dislocation of the patella is an extremely rare clinical entity, which is frequently misdiagnosed as acute patellar tendon rupture. Locked knee in extension is the classical presentation, and plain radiographs are most often diagnostic. Closed reduction can be accomplished in majority of cases, and we report superior patellar dislocation in an elderly female following trivial trauma, successfully managed by closed reduction under local anesthesia.

Keywords: Closed reduction, patellar dislocation, superior dislocation of the patella

How to cite this article:
Sunil P P, Renjith K R, Kumar P V, Vijayan AP. Superior dislocation of the patella: A rare cause for locked knee in extension. J Orthop Assoc South Indian States 2020;17:77-8

How to cite this URL:
Sunil P P, Renjith K R, Kumar P V, Vijayan AP. Superior dislocation of the patella: A rare cause for locked knee in extension. J Orthop Assoc South Indian States [serial online] 2020 [cited 2023 Apr 1];17:77-8. Available from: https://www.joasis.org/text.asp?2020/17/2/77/310981

  Introduction Top

Superior dislocation of the patella (SDP) is a rare type of extra-articular patellar dislocation, which may occur even without significant trauma. Most often misdiagnosed as acute patellar tendon rupture, extreme pain on attempted knee flexion remains a characteristic feature for clinical diagnosis of this uncommon condition. Although commonly described as a disease of the elderly in their sixth decade, there have been reports of similar injuries in young patients as well. We describe a case of SDP following a trivial hit injury in a 58-year-old female, successfully managed by closed reduction under local anesthesia.

  Case Report Top

A 58-year-old, previously healthy female attended our outpatient department with pain and inability to bend her right knee immediately following a direct hit injury against a door-edge 24 h back. The patient was unable to walk and came in a wheel-chair with her right knee locked in full extension. Clinical examination revealed unduly prominent superior pole of the patella with no palpable defect in the patellar tendon. She could perform active straight-leg raise (SLR) without any difficulty, but any attempt at knee flexion produced excruciating pain anteriorly. Lateral projection of plain radiographs showed SDP with interlocking osteophytes at the inferior pole of the patella and proximal articular surface of the trochlea [Figure 1]. The patient was counseled for closed reduction under local anesthesia, and after conscious sedation, we administered 5 ml of 2% lidocaine hydrochloride diluted in 15 ml of 0.9% normal saline into her knee joint for pain relief. The inferior pole of the patella was grasped between thumb and index finger followed by gentle sideways movement, resulting in successful reduction and immediate pain relief [Figure 2].
Figure 1: Lateral radiograph of the right knee showing superior dislocation of patella with interlocking osteophytes at the inferior pole of the patella and proximal articular surface of the trochlea

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Figure 2: Postreduction lateral radiograph showing reduced patella

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She demonstrated complete range of pain-free motion and was discharged home the same day with knee supported in an immobilizer for 2 weeks. There were no signs of recurrence at her final follow-up at 6 months.

  Discussion Top

Since Watson-Jones' first report on SDP in 1956, there have been around 20 case reports so far in the existing literature.[1] Elderly population (age range; 43–81 years) were affected more commonly, probably due to the presence of preexisting degenerative changes.[2],[3] Patella alta, ligamentous laxity, genu recurvatum, and neurological diseases have also been identified as predisposing factors for this rare disease entity.[4] It can be either traumatic, as in our patient, following a direct hit over the lower pole of patella or atraumatic, due to a sudden forceful contraction of quadriceps in a hyperextended knee. There have been reports on voluntary and spontaneous dislocations as well.[5],[6]

Clinical examination and plain radiography, most often, lead to a correct diagnosis, although other imaging modalities have also been used in uncertain cases. Patellar tendon rupture is the most common misdiagnosis made from initial radiographs; however, a careful examination can reveal anterior tilt of the upper patella with a palpable dimple inferiorly, intense pain on attempted knee flexion, and absence of any patellar tendon defects in SDP where the knee is classically locked in extension. Our patient could actively do an SLR before reduction even though this may vary between patients where an inability can further mislead to an incorrect diagnosis of patellar tendon rupture.

SDP is usually reducible by closed means in the majority of cases, yet opinions differ regarding the need for sedation or anesthesia support. We performed hydrodilatation of the knee with diluted local anesthetic, as described by Jahangir et al., which has got an additional mechanical advantage of disengaging the patella from anterior femur, apart from the analgesic action.[7] The reduction maneuver involves ipsilateral hip flexion with knee extension, which relieves the quadriceps tension, when a gentle mediolateral manipulation of the inferior pole, resulting in spontaneous relocation of patella with an audible clunk. Irreducible dislocation may need general anesthesia or very rarely open or arthroscopic reduction and removal of osteophytes.[2],[3]

  Conclusion Top

One must be aware of SDP, although rare, as an important differential diagnosis of anterior knee pain, especially in the elderly population, where a prompt clinical diagnosis can avoid unnecessary investigations and delay in treatment.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Watson-Jones R. Fractures and Joint Injuries. 5th ed. Baltimore: Williams Wilkins; 1956. p. 792-3.  Back to cited text no. 1
Teuscher DD, Goletz TH. Recurrent atraumatic superior dislocation of the patella: Case report and review of the literature. Arthroscopy 1992;8:541-3.  Back to cited text no. 2
Yoshino N, Takai S, Nakamura S, Manabe T, Hirasawa Y. Recurrent horizontal dislocation of the patella in the sagittal plane. A case report. J Bone Joint Surg Am 1996;78:278-80.  Back to cited text no. 3
Yip DK, Wong JW, Sun LK, Wong NM, Chan CW, Lau PY. Management of superior dislocation of the patella with interlocking osteophytes – An update on a rare problem. J Orthop Surg (Hong Kong) 2004;12:253-7.  Back to cited text no. 4
Takai S, Yoshino N, Hirasawa Y. Arthroscopic treatment of voluntary superior dislocation of the patella. Arthroscopy 1998;14:753-6.  Back to cited text no. 5
McWilliams TG, Binns MS. A locked knee in extension: A complication of a degenerate knee with patella Alta. J Bone Joint Surg Br 2000;82:890.  Back to cited text no. 6
Jahangir N, Umar M. Spontaneous superior patellar dislocation in young age: Case report and reduction technique. J Surg Case Rep 2017;2017:rjx036.  Back to cited text no. 7


  [Figure 1], [Figure 2]


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