Significantly greater lateral patellar displacement and tilt was found in osteoarthritis patients compared to a control group [3]. The adductor magnus tendon (AT) attaches to the adductor tubercle, which lies posterior and superior to the femoral attachment of the MPFL. b Axial MRI at the level of the tibial tuberosity. Because the knee is flexed in dislocation, the patella impacts upon the weightbearing surface of the lateral femoral condyle. This short surgical video demonstrates an arthroscopic lateral release as seen from inside the knee. These are most often found at the inferomedial patella or the lateral femoral condyle [49, 61, 62]. The transverse band attaches to the upper pole of the patella, and this component originates on a bony groove that lies between the adductor tubercle and the medial epicondyle, slightly posterior to the epicondyle. Excessive lateralization of the tibial tuberosity allows the patella to be pulled laterally in flexion and is considered to be a risk factor for instability. Fractures may be caused either by excessive force through the extensor mechanism or by a direct blow. Yu JS, Goodwin D, Salonen D, Pathria MN, Resnick D, Dardani M, Schweitzer M. AJR Am J Roentgenol. Radiology 216:582585, Ward SR, Terk MR, Powers CM (2007) Patella alta: association with patellofemoral alignment and changes in contact area during weight-bearing. Knee Surg Sports Traumatol Arthrosc 22:26552661, Seitlinger G, Scheurecker G, Hgler R, Labey L, Innocenti B, Hofmann S (2012) Tibial tubercle-posterior cruciate ligament distance: a new measurement to define the position of the tibial tubercle in patients with patellar dislocation. J Knee Surg 28:303309, Hevesi M, Heidenreich MJ, Camp CL et al (2019) The recurrent instability of the patella score: a statistically based model for prediction of long-term recurrence risk after first-time dislocation. Part of High resolution magnetic resonance imaging of the patellar retinaculum: normal anatomy, common injury patterns . MR Imaging of Patellar Instability: Injury Patterns and Assessment of Such patients are generally treated with immobilization for 3 to 6 weeks. Traumatic lateral patellar dislocation is a common injury among young, athletic individuals and is generally transient in nature. b Axial CT image showing tibial tuberosity transfer surgery with screw placement (arrow). Reconstruction of the MPFL has recently become an increasingly popular procedure for recurrent lateral patellar instability. A focused history of the mechanism, number, and circumstances of instability to date is essential. Isacsson A, Olsson O, Englund M, Frobell RB. Recent literature does not encourage the use of lateral release, since this can increase patellar instability. 35 Dislocation typically occurs in the setting of internal rotation of the femur on a fixed, externally rotated tibia. 8 Lippacher S, Dejour S, Elsharkawi M, et al. Radiographics 30:961981, Tscholl PM, Wanivenhaus F, Fucentese SF (2017) Conventional radiographs and magnetic resonance imaging for the analysis of trochlear dysplasia: the influence of selected levels on magnetic resonance imaging. U.S. Army Health Clinic Grafenwoehr U.S. Army Health Clinic Grafenwhr is located on Tower Barracks and provides quality ambulatory care for more than 15,000 Soldiers and their families, while coordinating and facilitating inpatient and specialty care with nearby German host nation medical facilities and DoD partners. the patellar retinaculum at the dynamic examination (Fig. The patellar apprehension test is used to assess for lateral instability and is positive when pain or discomfort occurs with lateral translation of the patella. Objective: Must rule out a tight iliotibial band (ITB) and weak quadriceps muscles (Juhn). The convex articular surface of the patella places it at risk for chondral injury in either the dislocation or the reduction phases of injury. Early diagnosis is essential, as chronic maltracking will lead to patellofemoral cartilage damage and osteoarthritis [3]. Acute lateral patellar dislocation at MR imaging: injury patterns of In fact, most patellar maltracking occurs between extension and the first 30 of flexion. In one MRI study, 76% of cases of prior lateral patellar dislocation showed medial retinacular injury at its patellar insertion and 30% at its midsubstance, and injury of the femoral origin of the MPFL was identified in 49% of the cases [49]. Lastly, a sulcus-deepening procedure known as trochleoplasty may be indicated in the patient with significant trochlear dysplasia and recurrent instability. Crossref, Medline, Google Scholar; 32 Starok M, Lenchikl L, Trudell D, Resnick D. Normal patellar retinaculum: MR and sonographic imaging with cadaveric correlation. Am J Sports Med 28:472479, Lewallen L, McIntosh A, Dahm D (2015) First-time patellofemoral dislocation: risk factors for recurrent instability. Epidemiology Patellar dislocation accounts for ~3% of all knee injuries and is commonly seen in those individuals who participate in sports activities. The injured retinaculum had an indistinct, irregular appearance associated with edema and hemorrhage. Skeletal Radiol 41:925931, Wittstein JR, Bartlett EC, Easterbrook J, Byrd JC (2006) Magnetic resonance imaging evaluation of patellofemoral malalignment. Depends on how bad: Small tears are observed and heal. We confirm that this article is not under consideration for publication elsewhere and that the authors did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors. b The patella tilt angle is measured between the posterior condylar line (dashed line) and the maximal patella width (solid line). It runs obliquely and transversely and inserts on the patella and the patellar tendon, and is composed of two layers. 2020;49(6):1642-50. The MPFL is best seen on axial MRI on the slice just distal to the VMO. This results in a slightly superolateral direction of pull on the patella by the quadriceps. The injury typically occurs from a twisting event with the knee in mild flexion (less than 30). https://doi.org/10.1186/s13244-019-0755-1, DOI: https://doi.org/10.1186/s13244-019-0755-1. Google Scholar, Sanders TG, Paruchuri NB, Zlatkin MB (2006) MRI of osteochondral defects of the lateral femoral condyle: incidence and pattern of injury after transient lateral dislocation of the patella. The patella becomes unstable and undergoes a transient, violent lateral displacement. Insights Imaging 10, 65 (2019). 6). Twenty-six pelvic limbs were used for gross dissection, and four stifle regions from two animals were used for radiography and magnetic resonance imaging (MRI). Acute lateral patellar dislocation at MR imaging: injury patterns of medial patellar soft-tissue restraints and osteochondral injuries of the inferomedial patella. Radiology 1993; 189:905-907. The oblique decussation of the MPFL blends with fibers of the superficial MCL. Note the edema in the superolateral aspect of Hoffas fat pad (arrow). All authors read and approved the final manuscript. The lateral trochlear articular surface is usually more prominent than its medial portion. Operative lateral retinaculum release is indicated in refractory cases. Figure 1: ligaments (Gray's illustrations), View Pereshin Moodaley's current disclosures, see full revision history and disclosures, posterior suprapatellar (prefemoral or supratrochlear) fat pad, anterior suprapatellar (quadriceps) fat pad, accessory anterior inferior tibiofibular ligament, superficial posterior tibiotalar ligament, superficial posterior compartment of the leg (calf), accessory extensor digiti secundus muscle, descending branch of the lateral circumflex. Patellar tracking refers to the dynamic relationship between the patella and trochlea during knee motion [1]. It should be noted that these procedures are mostly contraindicated in the patient with open physes due to growth arrest of the tibial tubercle apophysis. By altering the insertion point of the patellar tendon, these procedures affect the timing and position of patellar engagement in the trochlea and have the ability to biomechanically offload damaged distal articular cartilage, thereby reducing pain and increasing stability simultaneously. Acta Orthop 76:699704, Nikku R, Nietosvaara Y, Kallio PE, Aalto K, Michelsson JE (1997) Operative versus closed treatment of primary dislocation of the patella. 30 Correctly diagnosing APD can be difficult as the displaced patella usually relocates spontaneously, with fewer than 10% of patients presenting with fixed lateral dislocation. The stability of the patella is dependent on both osseous anatomy and the integrity of longitudinal and transverse soft tissue stabilizers. Clinical History: A 23 year-old female presents with medial knee pain following a twisting injury. Although edema can be seen in other peripatellar fad pads on MRI, there is no clear association between patellar maltracking and prefemoral fat pad edema or with that at the suprapatellar fat pad [56]. Epub 2023 Feb 7. Patellar dislocation accounts for ~3% of all knee injuries and is commonly seen in those individuals who participate in sports activities. eCollection 2015. (1a) A single fat-suppressed proton density-weighted coronal image is provided. In addition, symptomatic knees may demonstrate normal engagement between the patella and trochlea beyond 30 of flexion. PubMed J Bone Joint Surg Am Volume 90:27512762, Dixit S, Deu RS (2017) Nonoperative treatment of patellar instability. Check for errors and try again. ADVERTISEMENT: Radiopaedia is free thanks to our supporters and advertisers. These morphological risk factors can be assessed using methods similar to those on MRI as detailed in the prior sections of this article. Skeletal Radiology 39:7, 675-682. MR imaging of patellar retinacular ligament injuries - PubMed (28a) A sagittal proton density-weighted image demonstrates the typical hardware location in a patient status post medialization of the tibial tuberosity (arrow). Trochlear depth assessment. It takes a very strong force to tear the patellar tendon. Sports Med Arthrosc Rev 15:7277, Mikashima Y, Kimura M, Kobayashi Y, Miyawaki M, Tomatsu T (2006) Clinical results of isolated reconstruction of the medial patellofemoral ligament for recurrent dislocation and subluxation of the patella. 1835 31 - 40 27 30.0 41 - 50 22 24.4 50 + 4 4.4 Total 90 100.0 Age Distribution Number Percent Sex Female 19 21.1 Male 71 78.9 The contralateral side may serve as an internal control or may also have anatomic factors predisposing to maltracking. Soft tissue changes may include effusion, thickening or disruption of the MPFL, and retinacular complex and regional edema. TTTG is the distance between the solid and the dashed lines in (b). PDF ORIGINAL RESEARCH Role of Magnetic Resonance Imaging in Evaluation of Current Concepts Regarding Patellofemoral Trochlear Dysplasia. (13a) A line is drawn between the cortex of the lateral trochlear facet on the most superior axial image showing cartilage. Lateral patellar retinaculum | Radiology Reference Article In eight of 17 patients, the mechanism of injury was a patellar tendon tear (n = 1) or valgus hyperextension (n = 7). 2023 BioMed Central Ltd unless otherwise stated. Macroscopic Anatomy of the Stifle Joint in the Pampa's Deer A generalized physical examination assessing ligamentous laxity and rotational profile of the lower extremity is critical. Objective: This prospective study is designed to detect changes in the treatment of ruptured intracranial aneurysms over a period of 17 years. Deep lacerations are often associated with this type of injury. 2. Characterization of the type of medial restraint injury is crucial for surgical planning. The patella remains laterally subluxed and tilted, and the patient has an abnormally shallow trochlear groove (line). From this insertion, it extends posteriorly to blend with the lateral margin of the knee capsule and inferior surface of the lateral tibial condyle 1,2. no financial relationships to ineligible companies to disclose. Reference article, Radiopaedia.org (Accessed on 02 May 2023) https://doi.org/10.53347/rID-27273, {"containerId":"expandableQuestionsContainer","displayRelatedArticles":true,"displayNextQuestion":true,"displaySkipQuestion":true,"articleId":27273,"questionManager":null,"mcqUrl":"https://radiopaedia.org/articles/lateral-patellar-dislocation/questions/2391?lang=us"}, Case 14: transient lateral patellar dislocation, see full revision history and disclosures, anterior cruciate ligament avulsion fracture, posterior cruciate ligament avulsion fracture, Ahlback classification system in assessing osteoarthritis of the knee joint, Kellgren and Lawrence system for classification of osteoarthritis, anterior cruciate ligament mucoid degeneration, MRI grading system for meniscal signal intensity, medial retinacular abnormalities (ranging from strain to complete disruption) with adjacent periligamentous edema and hemorrhage, lateral displacement of patella (not necessarily seen in transient dislocation), medial patellar contusion +/- corresponding lateral femoral condyle contusion, direct trauma to lateral knee:normally no patellar contusion. It was shown that certain features of patellar maltracking (increased sulcus angle, lateral patellar tilt, and a higher patellar tendon to patellar length ratio) are associated with cartilage loss and bone marrow lesions [59]. Cookies policy. AJR Am J Roentgenol 179:11591166, Zhang GY, Zheng L, Ding HY, Li EM, Sun BS, Shi H (2015) Evaluation of medial patellofemoral ligament tears after acute lateral patellar dislocation: comparison of high-frequency ultrasound and MR. Eur Radiol 25:274281, Tecklenburg K, Dejour D, Hoser C, Fink C (2006) Bony and cartilaginous anatomy of the patellofemoral joint. PMID: 9168713. Knee Surg Sports Traumatol Arthrosc 14:235240, Article They are best indicated in isolation in the setting of recurrent instability with minimal underlying osseous malalignment (normal TT-TG, minimal trochlear dysplasia).
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