anterior knee pain by dr. brian sabb
DESCRIPTION
Award Winning Anterior Knee Pain Educational Exhibit at The American Roentgen Ray Society (ARRS)Annual MeetingTRANSCRIPT
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University of MichiganDepartment of Radiology
Anterior Knee Pain:A Diagnostic Conundrum
Brian Sabb, DOJ. David Blaha, MD
Department of Orthopaedic Surgery
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Disclosure of Commercial Interest
Neither I nor my immediate family members have a financial relationship with a commercial organization that may have a direct or indirect interest in the content.
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Objectives
• Improve the participant’s understanding of the radiologic diagnosis of anterior knee pain
• The participant will know specific imaging findings of anterior knee pathology
• Understand the biomechanics and pathophysiology of the patellofemoral joint and how they should be applied to the imaging evaluation
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Anterior Knee PainAnatomical Categorization
• Prepatellar Soft Tissues
• Quadriceps Fat Pad
• Infrapatellar Fat Pad of Hoffa
• Extensor Mechanism
• Patellofemoral Joint
• Patella
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Prepatellar Bursitis
• Inflammation of the prepatellar bursa
• In more severe cases one will see formation of a discrete fluid collection
• Can become infected, i.e. septic bursitis
• In chronic cases, may contain multiple calcified bodies
• US may show hyperemia; suggesting inflammation, infection, or acute trauma
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Prepatellar Bursitis
PD PD FAT SAT
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Prepatellar Bursitis
PD PD FAT SAT
T2 FAT SAT
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Quadriceps Fat Pad Edema
• Shown in a recent study to clinically mimic meniscal tear in 55% of patients and to present with anterior knee pain in 28% of patients
• Present in about 4-12 % of knee MRIs
• Edema may be present with or without mass effect
Shabshin, Skeletal Radiology. 2006 May; 35(5): 269-74 Roth, AJR. 2004 Jun;182(6):1383-7
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Quadriceps Fat Pad Edema
PD PD FAT SAT T2 FAT SAT
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Infrapatellar Fat Pad of Hoffa
• Hoffa’s disease
• Localized nodular synovitis
• Pigmented villonodular synovitis (PVNS)
• Intraarticular chondroma
• Infrapatellar plica syndrome
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Hoffa’s Disease
• A syndrome of fat pad impingement
• Acute or repetitive trauma causes inflammatory changes in the infrapatellar fat
• The resulting pain, swelling, and fat hypertrophy limits range of motion
• Over time, fibrotic tissue is formed
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Hoffa’s Disease
PD PD FAT SAT
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Localized Nodular Synovitis
• Benign proliferative disease
• Most commonly affects the tendon sheaths of the hands, e.g. giant cell tumor of tendon sheath
• MRI demonstrates a well defined mass in Hoffa’s fat pad
• Typically low SI on T1 and variable SI on T2
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Localized Nodular Synovitis
PD PD FAT SAT T2 FAT SAT
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Pigmented Villonodular Synovitis (PVNS)
• Benign proliferative disorder of the synovium
• Usually involves large joints
• 80% of cases affect the knee
• Synovial deposition of hemosiderin results in irregular synovial masses that show a significant amount of hypointensity on all sequences
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Pigmented Villonodular Synovitis (PVNS)
PD PD FAT SAT T2 FAT SAT
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Intraarticular Chondroma
• Although a rare lesion; they overwhelmingly occur around the knee, typically the infrapatellar fat pad
• May calcify and even ossify
• May erode the lower pole of the patella
• May displace the patellar tendon
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Intraarticular Chondroma
PD PD FAT SAT
T2 FAT SAT
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Infrapatellar Plica Injury
• A thin fold of synovial tissue, extending from the inferior pole of the patella through Hoffa’s fat to the intercondylar notch anterior to the anterior cruciate ligament
• High signal along the course of the plica indicates injury to the plica
• Thickening of the plica even in the absence of edema or fluid suggests a chronic injury
Cothran, AJR 2003; 180(5): 1443-1447
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Infrapatellar Plica Injury
PD PD FAT SAT T2 FAT SAT
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Extensor Mechanism Pathology
• Traumatic– Tendinosis– Patellar tendon tear– Quadriceps tendon tear
• Intrinsic patellar tendon lesions, e.g. gout
• Patellar enthesopathy
• Osteochondroses, e.g. Osgood-Schlatter Disease
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Patellar Tendinosis
• Pain in the infrapatellar region
• Commonly seen in athletes
• MRI demonstrates thickening of the patellar tendon with intermediate T1 or PD signal and increased signal on T2 especially with fat suppression
• Ultrasound demonstrates thickening, hypoechogenicity, and increased color flow
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Patellar Tendinosis
PD PD FAT SAT T2 FAT SAT
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Patellar Tendon Tear
• MRI– Fluid signal is seen at site of tear;
decreased T1 and increased T2 signal– A tendon gap is seen along with diastasis
of tendon fibers in full thickness tear• US
– Hypoechoic foci– Posterior shadowing is seen at ends of
the retracted tendon in full thickness tear– Patella alta
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Complete Patellar Tendon Tear
PD FAT SAT
Longitudinal Ultrasound
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Quadriceps Tendon Tear
• MRI– Partial thickness tear reveals small
pockets of fluid indicating tear often superimposed on the more diffuse increased T2 signal of tendinosis
• Ultrasound– Partial thickness tears demonstrate
hypoechogenicity and swelling• By both modalities, tendon retraction and
discontinuity of fibers indicates full thickness tear
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Quadriceps Tendon Tear
Full thickness tear by MR with diastasis of fibers filled by high T2 fluid and and by longitudinal US with hypoechoic fluid
PD FAT SAT
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PD FAT SAT
Complete Quadriceps Tendon Tear
PDNote: patella baja
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Intrinsic Patellar Tendon Lesion: Gout
• MRI reveals low T1 and mildly high T2 signal. There is an infiltrating mass present
• Ultrasound reveals hyperechogenicity, acoustic shadowing, and calcifications. Employing color flow imaging is important since peripheral hyperemia is expected
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Gout of The Patellar Tendon
PD PD FAT SAT
T2 FAT SAT
T2 FAT SAT
T2 FAT SAT
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Gout of The Patellar Tendon by US
Intratendinous Crystals
Peripheral hyperemia
Shadowing
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Enthesopathy of The Patella
• May be related to a degenerative process
• One must also consider inflammatory arthropathies
– Psoriasis
– Ankylosing spondylitis
– Reactive arthritis
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Psoriasis
PD PD FAT SAT PD FAT SAT
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Ankylosing Spondylitis
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Ankylosing Spondylitis
PD PD FAT SAT T2 FAT SAT
T1
Extensive bone marrow edema and associated enthesitis
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Reactive Arthritis
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Osgood Schlatter Disease
• An osteochondrosis of the tibial tubercle manifesting as anterior knee pain in adolescents
• The fragmentation can persist into adulthood and cause continued or recurrent symptoms
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Sequela of Osgood Schlatter
PD PD FAT SAT
T2 FAT SAT
T1
Note the irregularity and edema causing recurrent and chronic pain
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Patellar Malalignment
• Transient Patellar Dislocation
• Excessive Lateral Pressure Syndrome (ELPS)
• Patellar Tendon Lateral Femoral Condyle Friction Syndrome
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Transient Patellar Dislocation
• The medial patellar facet impacts against the lateral femoral condyle, producing bone bruises or microfractures. The pattern is nearly pathognomonic
• Injury to the medial patellar retinaculum is very common
• Predisposing factors include dysplastic trochlea, patella alta, lateralized tibial tubercle, and tight lateral retinaculum
• Treatment for recurrent dislocation often includes lateral retinacular release to decrease lateralization force on the patella
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Transient Patellar Dislocation
Lateral femoral condyle
T2 FAT SAT
Medial patella
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Excessive Lateral Pressure Syndrome (ELPS)
• Classically categorized as tilt without subluxation. Look for narrowing at the lateral aspect of the patellofemoral joint, especially in young patients with anterior knee pain
• However, only rarely see advanced tilt without subluxation
• Surgical treatment includes lateral retinacular release to decrease the translational force on the patella
• Attempt to make the diagnosis before advanced osteoarthritis (OA) ensues
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January 2001
at 27 years old
August 2005
at 31 years old
Excessive Lateral Pressure Syndrome
T2 FAT SAT T2 FAT SAT
The OA renders treatment/surgery less effective
Suggest the diagnosis based on the tilt; prior to OA
Images courtesy of Mark Schweitzer, MD
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Chung, Skeletal Radiology 2001 Nov; 39: 694-697
Patellar Tendon-Lateral Femoral Condyle Friction Syndrome
• Presents as anterior knee pain exacerbated by hyperextension
• MRI reveals edema in the superolateral aspect of Hoffa’s fat pad between the patellar tendon and the lateral femoral condyle
• Likely related to, or a form of patellar malalignment
• Associated with patella alta
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Patellar Tendon Lateral Femoral Condyle Friction Syndrome
PD FAT SAT Cor FAT SAT T2 FAT SAT
The alta allows for the contact between the tendon and the femoral condyle
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Patellar Abnormalities
• Bipartite patella
• Multipartite patella
• Patellar fracture
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Bipartite Patella
• Painful bipartite patella is a cause of anterior knee pain
• Any bipartite or multipartite bone can develop a pseudarthrosis
• The pseudarthrosis is manifested on MRI as bone marrow edema and as fluid between the osseous fragments
• Initial treatment includes physical therapy, rest, and pain control
• When initial therapy fails, surgery is often performed
• Surgical options include:– Resection of the painful fragment– Lateral retinacular release– Detachment of the insertion site of the vastus lateralis
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Bipartite Patella
PD FAT SAT T2 FAT SAT
Cor T2 FAT SAT
Note the accessory ossicle is typically superolateral
Bone marrow edema and cystic changes correlate with pain
Cor T1
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Multipartite Patella
T2 FAT SAT
Cor T2 FAT SAT
Cor T2 FAT SAT
T1
Note the typical superolateral fragments
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Patellar Fracture
• Susceptible to fracture because of its superficial location and lack of protection
• Two-thirds are horizontal fractures
• Next most frequent are comminuted and vertical fractures
• Look for sharp fracture lines, joint effusion, and location of fracture lines away from the typical superolateral location of an accessory ossicle
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Patellar Fracture
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Patellar Fracture
Axial CT showing a lipohemarthrosis