Patellofemoral friction syndrome: magnetic resonance imaging correlation of morphologic and T2 cartilage imaging.
OBJECTIVE
This study aimed to investigate whether patellofemoral T2 cartilage changes are associated with lateral patellofemoral friction syndrome (PFS), as indicated by an edema-like signal within the superolateral infrapatellar (Hoffa) fat pad.


METHODS
In this institutional review board-approved retrospective study of 510 consecutive patients, 49 patients with 50 knee magnetic resonance imaging examinations demonstrating normal or low-grade patellofemoral cartilage abnormalities (whole-organ magnetic resonance imaging score [WORMS] score, ≤2) were included. Twenty-two examinations with PFS (cases) were compared with an age- and sex-matched cohort of 28 examinations without PFS (controls). A 3-T magnetic resonance imaging was performed with multi-echo, spin-echo T2 mapping. Two readers measured in consensus malalignment parameters, including patellar height index, tibial tuberosity to trochlear groove distance, and sulcus angle. Bulk T2 cartilage values in the lateral and medial patellofemoral compartment, central weight-bearing medial and lateral femoral condyles were measured independently. Interobserver agreement was quantified using concordance correlation coefficients. Demographics, anatomic measurements, whole-organ magnetic resonance imaging scores, and cartilage T2 values were compared between cases and controls using Fisher exact test, Wilcoxon rank sum test, and mixed-effects models.


RESULTS
Cases demonstrated higher patellar height index (P = 0.002) and tibial tuberosity to trochlear groove distance (P = 0.02). Interobserver agreement for T2 values was good overall (concordance correlation coefficient range, 0.65-0.93). Cases demonstrated higher medial facet patellar bulk T2 (38.1 [7.5] ms) versus controls (33.6 [7.3] ms) (P = 0.02); otherwise, there were no significant differences in regional T2 values.


CONCLUSIONS
T2 mapping in patients with PFS demonstrates increased cartilage T2 in the medial patellar facet, possibly reflecting collagen alteration from early chondromalacia (softening) or increased water content related to altered contact pressures.
From the *Department of Radiology, University of Miami Miller School of Medicine, Jackson Memorial Hospital, Miami, FL; †The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins Hospital, Baltimore, MD; ‡Siemens Medical Solutions, Malvern, PA; §Siemens Healthcare, Erlangen, Germany; and ∥Department of Radiology, University of Texas Southwestern, Dallas, TX.
Ty K
TK
Subhawong
Rashmi S
RS
Thakkar
Abraham
A
Padua
Aaron
A
Flammang
Avneesh
A
Chhabra
John A
JA
Carrino
D000293:Adolescent; D000328:Adult; D002358:Cartilage, Articular / Q000473:pathology*; D005260:Female; D017276:Friction; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D046788:Patellofemoral Pain Syndrome / Q000175:diagnosis* / Q000473:pathology