The Incidence of Kaplan Fiber Injury Associated With Acute Anterior Cruciate Ligament Tear Based on Magnetic Resonance Imaging.

BACKGROUND: Kaplan fibers are distinct deep layers of the distal iliotibial band (ITB) that anchor the ITB to the distal femur and have a role in rotational stability of the knee. However, the incidence of Kaplan fiber injury in the setting of acute anterior cruciate ligament (ACL) tear is unknown. PURPOSE: To determine the reliability of identifying and evaluating Kaplan fibers on magnetic resonance imaging (MRI) examinations based on previously reported characteristics and to report on the incidence of combined ACL and Kaplan fiber injuries based on MRI examinations. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 3. METHODS: Patients with an acute primary ACL tear who obtained a postinjury MRI scan at our institution and were treated with ACL reconstruction between January 1, 2007, and May 31, 2012, were identified from an institutional registry. Each patient's postinjury MRI scan was reviewed by 2 musculoskeletal radiologists, who identified Kaplan fibers and graded them as intact, injured, or not visualized. Intrarater reliability was measured using the intraclass correlation coefficient (ICC), and interrater reliability was measured using the kappa statistic. RESULTS: A total of 72 patients were identified. For the proximal Kaplan fibers, 50% versus 58% were identified as injured, 32% versus 29% were identified as intact, and 18% versus 13% were not visualized by radiologist 1 and 2, respectively. For the distal Kaplan fibers, 46% versus 60% were identified as injured, 43% versus 28% were identified as intact, and 11% versus 12% were not visualized by radiologist 1 and 2, respectively. The ICC intrarater reliability measurements were 0.89 (95% CI, 0.83-0.93) for proximal Kaplan fibers and 0.66 (95% CI, 0.51-0.78) for distal Kaplan fibers. The interrater reliability measurements for both radiologists showed substantial agreement (kappa = 0.7) for proximal Kaplan fibers and moderate agreement (kappa = 0.51) for distal Kaplan fibers. CONCLUSION: Kaplan fibers were visualized on MRI studies in the majority of cases, with substantial reliability for the proximal fibers and moderate reliability for the distal fibers. There was an associated injury to either the proximal or distal or both Kaplan fibers in the majority of acute primary ACL tears.

Relation of Patellofemoral Joint Alignment, Morphology, and Radiographic Osteoarthritis to Frequent Anterior Knee Pain: Data from the Multicenter Osteoarthritis Study.

OBJECTIVE: Patellofemoral (PF) alignment and trochlear morphology are associated with PF osteoarthritis (OA) and knee pain, but whether they are associated with localized anterior knee pain is unknown, which is believed to be a symptom specific to PF joint pathology. We therefore aimed to evaluate the relation of PF alignment and morphology, as well as PFOA and tibiofemoral OA, to anterior knee pain. METHODS: The Multicenter Osteoarthritis Study is a cohort study of individuals with, or at risk for, knee OA. We evaluated cross-sectional associations of PF alignment, trochlear morphology, and PF and tibiofemoral radiographic OA, with localized anterior knee pain (defined with a pain map). We used 2 approaches: a within-person knee-matched evaluation of participants with unilateral anterior knee pain (conditional logistic regression), and a cohort approach comparing those with anterior knee pain to those without (binomial regression). RESULTS: With the within-person knee-matched approach (n = 110; 64% women, mean age 70 years, body mass index [BMI] 30.9), PF alignment, morphology, and tibiofemoral OA were not associated with unilateral anterior knee pain. Radiographic PFOA was associated with pain, odds ratio 5.3 (95% confidence interval [95% CI] 1.6-18.3). Using the cohort approach (n = 1,818; 7% of knees with anterior knee pain, 59% women, mean age 68 years, BMI 30.4), results were similar: only PFOA was associated with pain, with a prevalence ratio of 2.2 (95% CI 1.4-3.4). CONCLUSION: PF alignment and trochlear morphology were not associated with anterior knee pain in individuals with, or at risk for, knee OA. Radiographic PFOA, however, was associated with pain, suggesting that features of OA, more so than mechanical features, may contribute to localized symptoms.

Relationship of Trochlear Morphology and Patellofemoral Joint Alignment to Superolateral Hoffa Fat Pad Edema on MR Images in Individuals with or at Risk for Osteoarthritis of the Knee: The MOST Study.

Purpose To determine the relationship of patellofemoral joint alignment and trochlear morphology to superolateral Hoffa fat pad (SHFP) edema on magnetic resonance (MR) images in older adults with or at risk for osteoarthritis of the knee. Materials and Methods Institutional review board approval and written informed consent were obtained from all subjects. The Multicenter Osteoarthritis Study is a prospective cohort study of older adults with or at risk for osteoarthritis of the knee. Subjects were recruited from Birmingham, Alabama, and Iowa City, Iowa. In this cross-sectional study, patellofemoral joint alignment (bisect offset, patellar tilt angle, and Insall-Salvati ratio), trochlear morphology (sulcus angle, lateral and medial trochlear inclination, and trochlear angle) and SHFP edema were assessed on MR images of the knee. Measures of alignment and morphology were divided into quartiles, and SHFP was determined to be present or absent. Separate logistic regression models were used to determine the relationship of each measure of alignment and morphology to the presence of SHFP edema, with adjustments for age, sex, and body mass index. Results SHFP edema was present in 152 (13.4%) of the 1134 knees that were included. When compared with knees with measurements in the lowest quartile, knees with measurements in the highest quartile for trochlear angle, bisect offset, and Insall-Salvati ratios were 1.6 (95% confidence interval [CI]: 1.0, 2.6), 2.3 (95% CI: 1.3, 4.0), and 8.9 (95% CI: 4.7, 16.9) times more likely to show SHFP edema, respectively. No relationship was found between other measures and SHFP edema. Conclusion A more anterior trochlear facet, a more laterally displaced patella, and knees with patella alta were significantly associated with SHFP edema on MR images in subjects with or at risk for osteoarthritis of the knee. © RSNA, 2017.