Introduction Can be classified into the following acute traumatic occurs equally by gender may occur from a direct blow (ex. helmet to knee collision in football) chronic patholaxity recurrent subluxation episodes occurs more in women associated with malalignment habitual usually painless occurs during each flexion movement pathology is usually proximal (e.g. tight lateral structures - ITB and vastus lateralis) Epidemiology demographics most commonly occurs in 2nd-3rd decades of life risk factors general factors ligamentous laxity (Ehlers-Danlos syndrome) previous patellar instability event "miserable malalignment syndrome" a term named for the 3 anatomic characteristics that lead to an increased Q angle femoral anteversion genu valgum external tibial torsion / pronated feet anatomical factors osseous patella alta causes patella to not articulate with sulcus, losing its constraint effects trochlear dysplasia excessive lateral patellar tilt (measured in extension) lateral femoral condyle hypoplasia muscle dysplastic vastus medialis oblique (VMO) muscle overpull of lateral structures iliotibial band vastus lateralis Pathophysiology mechanism usually on noncontact twisting injury with the knee extended and foot externally rotated patient will usually reflexively contract quadriceps thereby reducing the patella osteochondral fractures occur most often as the patella relocates direct blow less common ex. knee to knee collision in basketball, or football helmet to side of knee Anatomy Passive stability medial patellofemoral ligament (MPFL) femoral origin-insertion is between medial epicondyle and adductor tubercle is usual site of avulsion of MPFL is primary restraint in first 20 degrees of knee flexion patellar-femoral bony structures account for stability in deeper knee flexion trochlear groove morphology, patella height, patellar tracking Dynamic stability provided by vastus medialis (attaches to MPFL) Presentation Symptoms complaints of instability anterior knee pain Physical exam acute dislocation usually associated with a large hemarthrosis absence of swelling supports ligamentous laxity and habitual dislocation mechanism medial sided tenderness (over MPFL) increase in passive patellar translation measured in quadrants of translation (midline of patella is considered "0"), and also should be compared to contralateral side normal motion is <2 quadrants of patellar translation lateral translation of medial border of patella to lateral edge of trochlear groove is considered "2" quadrants and is considered abnormal amount of translation patellar apprehension passive lateral translation results in guarding and a sense of apprehension increased Q angle J sign excessive lateral translation in extension which "pops" into groove as the patella engages the trochlea early in flexion associated with patella alta Imaging Radiographs rule out fracture or loose body medial patellar facet (most common) lateral femoral condyle AP views best to evaluate overall lower extremity alignment and version lateral views best to assess for trochlear dysplasia crossing sign trochlear groove lies in same plane as anterior border of lateral condyle represents flattened trochlear groove double contour sign anterior border of lateral condyle lies anterior to anterior border of medial condyle represents convex trochlear groove/hypoplastic medial condyle supratrochlear spur arises in proximal aspect of trochlea evaluate for patellar height (patella alta vs. baja) Blumensaat's line should extend to inferior pole of the patella at 30 degrees of knee flexion Insall-Salvati method normal between 0.8 and 1.2 Blackburne-Peel method normal between 0.5 and 1.0 Caton Deschamps method normal between 0.6 and 1.3 Plateau-patella angle normal between 20 and 30 degrees Sunrise/Merchant views best to assess for lateral patellar tilt lateral patellofemoral angle (normal is an angle that opens laterally) angle between line along subchondral bone of lateral trochlear facet + posterior femoral condyles normal > 11° congruence angle (normal is -6 degrees) CT scan TT-TG distance measures the distance between 2 perpendicular lines from the posterior cortex to the tibial tubercle and the trochlear groove >20mm usually considered abnormal MRI help further rule out suspected loose bodies osteochondral lesion and/or bone bruising medial patellar facet (most common) lateral femoral condyle tear of MPFL tear usually at medial femoral epicondyle Adult Treatment Nonoperative NSAIDS, activity modification, and physical therapy indications mainstay of treatment for first time patellar dislocator without any loose bodies or intraarticular damage habitual dislocator techniques short-term immobilization for comfort followed by 6 weeks of controlled motion emphasis on strengthening closed chain short arc quadriceps exercises Quad strengthening core and hip strengthening to improve limb positioning and balance (hip abductors, gluteals, and abdominals) patellar stabilizing sleeve or "J" brace consider knee aspiration for tense effusion positive fat globules indicates fracture Operative Arthroscopic debridement (removal of loose body) vs Repair with or without stabilization indications displaced osteochondral fractures or loose bodies may be an indication for operative treatment in a first-time dislocator techniques arthroscopic vs open removal versus repair of the osteochondral fragment primary repair with screws or pins if sufficient bone available for fixation MPFL repair indications acute first time dislocation with bony fragment techniques direct repair when surgery can be done within first few days no clinical studies support this over nonoperative treatment MPFL reconstruction with autograft vs allograft indications recurrent instability no significant underlying malalignment techniques gracilis or semitendinosus commonly used (stronger than native MPFL) femoral origin can be reliably found radiographically (Schottle point) Fulkerson-type osteotomy (anterior and medial tibial tubercle transfer) indications may be used in addition to MPFL or in isolation for significant malalignment TT-TG >20mm on CT techniques anteromedialized displacement of osteotomy and fixation correct TT-TG to 10-15mm (never less than 10mm) tibial tubercle distalization indications patella alta techniques distal displacement of osteotomy and fixation lateral release indications isolated release no longer indicated for instability only indicated if there is excessive lateral tilt or tightness after medialization technique arthroscopic trochleoplasty indications rarely addressed (in the USA) even if trochlear dysplasia present may consider in severe or revision cases techniques arthroscopic or open trochlear deepening procedure Pediatric Treatment Same principles as adults in general but must preserve the physis do not do tibial tubercle osteotomy (will harm growth plate of proximal tibia) Complications Recurrent dislocation redislocation rates with nonoperative treatment may be high (15-50%) at 2-5 years recurrence rate is higher in those patients who sustain a primary dislocation under the age of 20 Medial patellar dislocation and medial patellofemoral arthritis almost exclusively iatrogenic as a result of prior patellar stabilization surgery
Technique Guide Technique guide are not considered high yield topics for orthopaedic standardized exams including the ABOS, EBOT and RC. Medial Retinacular Plication (Modified Insall ) Orthobullets Team Knee & Sports - Patellar Instability Technique Guide Technique guide are not considered high yield topics for orthopaedic standardized exams including the ABOS, EBOT and RC. MPFL Reconstruction - Pediatric and Adolescent Orthobullets Team Knee & Sports - Patellar Instability Technique Guide Technique guide are not considered high yield topics for orthopaedic standardized exams including the ABOS, EBOT and RC. MPFL Reconstruction - Adult Brandon Erickson Knee & Sports - Patellar Instability
QUESTIONS 1 of 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Previous Next Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ12.72) Which of the following structures attaches between the medial epicondyle and adductor tubercle of the femur? Review Topic QID: 4432 Type & Select Correct Answer 1 Medial head of gastrocnemius 7% (359/5507) 2 Medial collateral ligament 17% (958/5507) 3 Semimembranosus 3% (141/5507) 4 Adductor magnus 6% (338/5507) 5 Medial patellofemoral ligament 67% (3688/5507) L 3 Select Answer to see Preferred Response SUBMIT RESPONSE 5 You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ11.188) Which of the following best describes the radiographic landmarks on a lateral radiograph for locating the femoral attachment of the medial patellofemoral ligament (MPFL) during reconstruction? Review Topic QID: 3611 Type & Select Correct Answer 1 The intersection of a line extended from the middle of the shaft and Blumensaat's line 7% (229/3236) 2 Anterior to a line extended from the middle of the shaft and Blumensaat's line 6% (206/3236) 3 Posterior to a line extended from the posterior cortex of the shaft and distal to Blumensaat's line 7% (241/3236) 4 Anterior to a line extended from the posterior cortex of the shaft and distal to Blumensaat's line 13% (433/3236) 5 Anterior to a line extended from the posterior cortex of the shaft and proximal to Blumensaat's line 65% (2092/3236) L 3 Select Answer to see Preferred Response SUBMIT RESPONSE 5 Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ10.188) A 27-year-old football player sustains an acute lateral patellar dislocation. Which of the following is the most likely site of injury seen on MRI? Review Topic QID: 3281 Type & Select Correct Answer 1 Midsubstance oblique retinacular ligament rupture 13% (377/2877) 2 Soft-tissue avulsion of medial patellofemoral ligament 58% (1660/2877) 3 Midsubstance medial patellofemoral ligament rupture 19% (551/2877) 4 Partial quadriceps tendon rupture 3% (78/2877) 5 Bony avulsion of medial patellofemoral ligament 7% (196/2877) L 4 Select Answer to see Preferred Response SUBMIT RESPONSE 2 You have 100% on this question. Just skip this one for now. Take This Question Anyway This is an AAOS Self assessment question. Orthobullets was not involved into the editorial process, and does not have the ability to alter. If you prefer to hide SAE questions on topics simply turn them off in your Content Settings (SAE08AN.85) Figure 49 shows an acute axial MRI scan of a right knee. What is the most likely diagnosis? Review Topic QID: 6245 FIGURES: A Type & Select Correct Answer 1 Patellar tendon rupture 1% (4/273) 2 Lateral dislocation of the patella 89% (242/273) 3 Quadriceps tendon rupture 1% (3/273) 4 Anterior cruciate ligament rupture 7% (20/273) 5 Posterior cruciate ligament rupture 1% (4/273) L 1 Select Answer to see Preferred Response SUBMIT RESPONSE 2 You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ08.49) A high school softball player has chronic activity-related anterior knee pain without a history of instability. Which radiographic measurement is used to indicate when a lateral retinacular release may be helpful? Review Topic QID: 435 Type & Select Correct Answer 1 Congruence angle 15% (300/2057) 2 Q angle 22% (451/2057) 3 Sulcus angle 8% (168/2057) 4 Lateral patello-femoral angle 55% (1124/2057) 5 Patellar height index 0% (8/2057) L 4 Select Answer to see Preferred Response SUBMIT RESPONSE 4 You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ07.112) You see a patient in the emergency room with an acute lateral patellar dislocation. Which of the following factors is associated with the highest risk of persistent patellar instability? Review Topic QID: 773 Type & Select Correct Answer 1 Younger age 3% (24/729) 2 Increased Q-angle 11% (80/729) 3 Male gender 0% (1/729) 4 Previous patellar instability event 83% (607/729) 5 Amount of lateral patellar tilt 2% (11/729) L 2 Select Answer to see Preferred Response SUBMIT RESPONSE 4 You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ07.30) An athlete sustains a traumatic patellar dislocation. The MRI shows a hemarthrosis with a floating osteochondral fragment. Which of the following is the most likely site of origin for the loose fragment? Review Topic QID: 691 Type & Select Correct Answer 1 The lateral patellar facet 12% (207/1661) 2 The medial patellar facet 84% (1388/1661) 3 The odd patellar facet 1% (16/1661) 4 The medial trochlea 2% (35/1661) 5 The central trochlea 1% (12/1661) L 2 Select Answer to see Preferred Response SUBMIT RESPONSE 2 Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ04.46) All of the following are predisposing factors for lateral patellar dislocation in a native knee EXCEPT? Review Topic QID: 107 Type & Select Correct Answer 1 Excess femoral internal rotation 4% (29/803) 2 Excess external tibial rotation 15% (119/803) 3 Lateral femoral condylar hypoplasia 2% (14/803) 4 Increased Q-angle 2% (13/803) 5 Insufficiency of the vastus lateralis 78% (625/803) L 2 Select Answer to see Preferred Response SUBMIT RESPONSE 5
All Videos (27) Podcasts (1) Login to View Community Videos Login to View Community Videos 2018 Chicago Sports Medicine Symposium: World Series of Surgery Patellofemoral Cases: The Good, Bad and Ugly - Moderator: Adam B. Yanke, MD (CSMS #74, 2018) Adam Yanke Knee & Sports - Patellar Instability 11/24/2018 284 views Login to View Community Videos Login to View Community Videos 2018 Chicago Sports Medicine Symposium: World Series of Surgery Rehab for Patellofemoral Problems: It’s Complicated - George J. Davies, DPT (CSMS #73, 2018) Knee & Sports - Patellar Instability 11/24/2018 194 views Login to View Community Videos Login to View Community Videos 2018 Chicago Sports Medicine Symposium: World Series of Surgery Patellar Instability: Looking Outside the MPFL (Alta/Dysplasia/Malalignment) - Jack Farr, II, MD (CSMS #72, 2018) Jack Farr Knee & Sports - Patellar Instability 11/24/2018 327 views Login to View Community Videos Login to View Community Videos 2018 Chicago Sports Medicine Symposium: World Series of Surgery MPFL: Anatomy, Reconstruction, and Why it Matters - Adam B. Yanke, MD (CSMS #71, 2018) Adam Yanke Knee & Sports - Patellar Instability 11/24/2018 299 views Login to View Community Videos Login to View Community Videos 2018 Chicago Sports Medicine Symposium: World Series of Surgery First Time Patellar Dislocation - Seth Sherman, MD (CSMS #70, 2018) Seth Sherman Knee & Sports - Patellar Instability 11/24/2018 328 views Login to View Community Videos Login to View Community Videos 2018 Winter SKS Meeting: Shoulder, Knee, & Sports Medicine Case Presentations - James L. Carey, MD, MPH (4.16, 2018 Winter SKS) Mark Cohen Knee & Sports - Patellar Instability 8/15/2018 274 views Login to View Community Videos Login to View Community Videos 2018 Winter SKS Meeting: Shoulder, Knee, & Sports Medicine Video Spotlight: MPFL Reconstruction - Matthew T. Provencher, MD , CAPT, MC, USNR (2.39, 2018 Winter SKS) Matthew Provencher Knee & Sports - Patellar Instability 7/16/2018 362 views Login to View Community Videos Login to View Community Videos 2018 Winter SKS Meeting: Shoulder, Knee, & Sports Medicine When should I perform a Trochleoplasty? - Andreas B. Imhoff, MD (2.38, 2018 Winter SKS) Knee & Sports - Patellar Instability 7/16/2018 211 views Login to View Community Videos Login to View Community Videos 2018 Winter SKS Meeting: Shoulder, Knee, & Sports Medicine When should I perform an Osteotomy for Patellar Instability? - Robin West, MD (2.37, 2018 Winter SKS) Robin West Knee & Sports - Patellar Instability 7/16/2018 393 views Login to View Community Videos Login to View Community Videos 2018 Winter SKS Meeting: Shoulder, Knee, & Sports Medicine Imaging for Recurrent Patellar Instability in Athletes: What to look for? - Jo A. Hannafin, MD, PhD (2.36, 2018 Winter SKS) Jo Hannafin Knee & Sports - Patellar Instability 7/16/2018 238 views Login to View Community Videos Login to View Community Videos 2018 Winter SKS Meeting: Shoulder, Knee, & Sports Medicine First Time Patellar Dislocations, when is it Best to Intervene? - James P. Bradley, MD (2.35, 2018 Winter SKS) Knee & Sports - Patellar Instability 7/16/2018 479 views Login to View Community Videos Login to View Community Videos 2017 Orthopaedic Summit Evolving Techniques Pro: MPFL Reconstruction: Tips and Tricks for a Successful Outcome (Docking Technique) - Beth E. Shubin-Stein, MD Knee & Sports - Patellar Instability 4/30/2018 140 views Login to View Community Videos Login to View Community Videos 2017 Orthopaedic Summit Evolving Techniques The Dislocated Knee: Clinical & Imaging Evaluation and Avoiding Complications João Espregueira-Mendes, MD, PhD João Espregueira-Mendes Knee & Sports - Patellar Instability 4/24/2018 214 views Login to View Community Videos Login to View Community Videos 2017 Chicago Sports Medicine Symposium: World Series of Surgery MPFL Made Easy - Adam Yanke, MD (CSMS #75, 2017) Adam Yanke Knee & Sports - Patellar Instability 11/16/2017 247 views Login to View Community Videos Login to View Community Videos 2017 Chicago Sports Medicine Symposium: World Series of Surgery MPFL Reconstruction Rehabilitation Concepts in the Athlete - Russ Paine, PT (CSMS #59, 2017) Knee & Sports - Patellar Instability 11/16/2017 45 views Login to View Community Videos Login to View Community Videos 2017 Chicago Sports Medicine Symposium: World Series of Surgery Medial Patellofemoral Ligament - Adam Yanke, MD (CSMS #57, 2017) Adam Yanke Knee & Sports - Patellar Instability 11/16/2017 68 views Login to View Community Videos Login to View Community Videos 2016 Chicago Sports Medicine Symposium Patella/Multiligament Instability Cases: Good, Bad and Ugly - Adam Yanke, MD (CSMS #65, 2016) Adam Yanke Knee & Sports - Patellar Instability 10/26/2016 243 views Login to View Community Videos Login to View Community Videos 2016 Chicago Sports Medicine Symposium Rehabilitation of the Knee: When Can I Return to Sport? - George Davies, DPT (CSMS #64, 2016) Knee & Sports - Patellar Instability 10/26/2016 265 views Login to View Community Videos Login to View Community Videos 2016 Chicago Sports Medicine Symposium Patellar Instability: Looking Outside the MPFL (Alta/Dysplasia/Malalignment) - George Davies, DPT (CSMS #63, 2016) Knee & Sports - Patellar Instability 10/26/2016 404 views Login to View Community Videos Login to View Community Videos 2016 Chicago Sports Medicine Symposium MPFL: Anatomy, Reconstruction, and Why it Matters - Adam Yanke, MD (CSMS #62, 2016) Adam Yanke Knee & Sports - Patellar Instability 10/26/2016 286 views Login to View Community Videos Login to View Community Videos 2016 Chicago Sports Medicine Symposium Patellofemoral Pain and Articular Injury: What Can We Do - Adam Yanke, MD (CSMS #45, 2016) Adam Yanke Knee & Sports - Patellar Instability 10/25/2016 162 views Upgrade to View Premium Videos Upgrade to View Premium Videos MPFL reconstruction for patella dislocation Clayton Lane Knee & Sports - Patellar Instability 4/21/2013 878 views Upgrade to View Premium Videos Upgrade to View Premium Videos MPFL Reconstruction with Free Soft Tissue Graft - Dr. Mark Miller Knee & Sports - Patellar Instability 10/11/2012 4874 views Upgrade to View Premium Videos Upgrade to View Premium Videos Fulkerson Osteotomy - Dr. Mark Miller Knee & Sports - Patellar Instability 9/25/2012 5127 views Upgrade to View Premium Videos Upgrade to View Premium Videos Medial Patello Femoral Ligament Reconstruction Derek Moore Knee & Sports - Patellar Instability 1/16/2012 2603 views Upgrade to View Premium Videos Upgrade to View Premium Videos Dynamic J Sign in patellofemoral joint instability Derek Moore Knee & Sports - Patellar Instability 1/16/2012 207 views Upgrade to View Premium Videos Upgrade to View Premium Videos "Reverse" J sign of patellofemoral instability David Abbasi Knee & Sports - Patellar Instability 12/4/2011 266 views Sports ⎜ Patellar Instability Team Orthobullets (AF) Knee & Sports - Patellar Instability Listen Now 25:36 min 10/18/2019 84 plays See More See Less
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