Osteoarthritis of the knee joint is

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1 Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at Richard Kijowski, MD Paul Stanton, MD Jason Fine, PhD Arthur De Smet, MD Subchondral Bone Marrow Edema in Patients with Degeneration of the Articular Cartilage of the Knee Joint 1 Purpose: Materials and Methods: To retrospectively determine at magnetic resonance (MR) imaging the prevalence of subchondral bone marrow edema beneath arthroscopically proved articular cartilage defects. The study was performed in compliance with HIPAA regulations, and a waiver of informed consent was obtained from the institutional review board before the study was performed. The study consisted of 132 patients (70 men, 62 women; average age, 53 years) with articular cartilage defects of the knee joint who underwent MR imaging of the knee and subsequent arthroscopic knee surgery. At the time of arthroscopy, each articular cartilage lesion was graded by using the Noyes classification system. MR examinations were retrospectively reviewed to determine the size, depth, and location of subchondral bone marrow edema without knowledge of the arthroscopic findings. Pairwise Fisher exact tests and two-sample t tests were used to correlate MR imaging findings of subchondral bone marrow edema with the arthroscopic grade of articular cartilage degeneration. Results: Subchondral bone marrow edema was seen beneath 105 (19%) of 554 articular cartilage defects identified at arthroscopy. It was not observed beneath any of the six grade 1 cartilage defects but was observed beneath eight (4.9%) of 163 grade 2A defects, 40 (14.4%) of 278 grade 2B defects, 54 (55.1%) of 98 grade 3A defects, and three (33.3%) of nine grade 3B defects. Subchondral bone marrow edema was also seen beneath four (1.4%) of 238 articular surfaces that appeared normal at arthroscopy. The mean depth and cross-sectional area of subchondral bone marrow edema increased with increasing grade of the articular cartilage lesion. ORIGINAL RESEARCH MUSCULOSKELETAL IMAGING Conclusion: Higher grades of articular cartilage defects are associated with higher prevalence and greater depth and cross-sectional area of subchondral bone marrow edema. RSNA, From the Departments of Radiology (R.K., P.S., J.F., A.D.S.) and Statistics (J.F.), University of Wisconsin Hospital, Clinical Science Center-E3/311, 600 Highland Ave, Madison, WI Received January 25, 2005; revision requested March 31; revision received April 6; accepted May 6; final version accepted May 24. Address correspondence to R.K. ( rkijowski@mail.radiology.wisc.edu). RSNA, 2006 Radiology: Volume 238: Number 3 March

2 MUSCULOSKELETAL IMAGING: Subchondral Edema of the Knee Joint Kijowski et al Osteoarthritis of the knee joint is extremely common. Nearly 75% of individuals aged 65 years or older in the United States have evidence of degenerative joint disease on knee radiographs. Furthermore, approximately 1.6% of the American population has symptomatic osteoarthritis of the knee joint (1,2). Pain is the major source of disability in patients with osteoarthritis of the knee joint (3). The exact cause of pain in patients with degenerative joint disease is presently unknown. Degeneration of articular cartilage is the pathologic hallmark of osteoarthritis; however, articular cartilage has no nociceptive pain fibers and thus cannot be the source of pain in patients with degenerative joint disease (4,5). Subchondral bone marrow is richly innervated with nociceptive pain fibers and may be a source of pain in patients with symptomatic degenerative joint disease (4,5). Abnormalities of subchondral bone marrow are common manifestations of various painful disorders of the knee, including posttraumatic contusions, transient osteoporosis, infectious and inflammatory arthropathies, insufficiency fractures, and spontaneous osteonecrosis. These painful osseous disorders are characterized by the presence of subchondral bone marrow edema on magnetic resonance (MR) images (6 9). Subchondral bone marrow edema is also commonly seen in patients with degenerative joint disease (10 14). Subchondral bone marrow edema in patients with osteoarthritis of the knee joint has been associated with knee pain and the progression of articular cartilage degeneration (12,13). The association between subchondral bone marrow edema and degeneration of the articular cartilage of the Advance in Knowledge The overall prevalence of subchondral bone marrow edema in patients with surgically confirmed articular cartilage degeneration of the knee joint is 19%, and the prevalence varies with the severity of the defect. knee joint has been well documented (10 14); however, the prevalence of subchondral bone marrow edema beneath areas of articular cartilage degeneration has not been previously reported. Thus, the purpose of our study was to retrospectively determine at MR imaging the prevalence of subchondral bone marrow edema beneath arthroscopically proved articular cartilage defects of the knee joint. Materials and Methods Study Group The study was performed in compliance with Health Insurance Portability and Accountability Act regulations. Our institutional review board approved the study and granted a waiver of informed consent before the study was performed. The study group consisted of 132 patients with articular cartilage defects of the knee joint who underwent an MR examination of the knee prior to arthroscopic knee surgery. An MR database was retrospectively reviewed by one author (P.S.), who identified 1235 patients with articular cartilage defects of the knee joint on MR images obtained at our institution between January 1999 and June The medical records of these 1235 patients were reviewed by the same author, and 152 patients were identified who were seen by any one of three orthopedic sports medicine specialists at our institution and who underwent subsequent arthroscopic surgery on their symptomatic knee. The medical records and MR images of these 152 patients were retrospectively reviewed by two authors (R.K. and P.S.). Patients with clinical manifestations or MR imaging findings of metabolic bone disease, septic arthritis, inflammatory arthritis, connective tissue disease, insufficiency fracture, spontaneous osteonecrosis, or neoplastic disease were excluded from the study. In addition, patients with a history of trauma within 12 months of the MR examination or history of knee surgery were excluded from the study. Twenty of the 152 patients were excluded from the study on the basis of these criteria. The study group consisted of the remaining 132 patients (70 men and 62 women) with arthroscopically proved articular cartilage defects of the knee joint. The patients were aged between 31 and 77 years, with an average age of 53 years. All 132 patients were evaluated by any one of three orthopedic surgeons at our institution who specialized in sports medicine and who had between 5 and 20 years of clinical experience treating patients with musculoskeletal disorders. The clinical notes of all patients were thoroughly reviewed by two authors (R.K. and P.S.) to determine the location of each patient s knee pain if it was specified. The location of knee pain was not specified in the clinical notes nor was described as being diffusely distributed throughout the knee in 22 of the 132 patients. MR Imaging All 132 patients had undergone MR imaging of the symptomatic knee within 2 months after their clinic visit. All MR examinations were performed with the same 1.5-T field strength magnet (GE Medical Systems, Milwaukee, Wis) by using a phased-array extremity coil. All MR examinations of the knee consisted of coronal T1-weighted spin-echo (repetition time msec/echo time msec, /15 30), coronal fat-suppressed intermediate-weighted fast spin-echo ( /30 50, echo train length of four), sagittal intermediate-weighted fast spinecho ( /30 50, echo train length of four), sagittal fat-suppressed Published online before print /radiol Radiology 2006; 238: Author contributions: Guarantor of integrity of entire study, R.K.; study concepts/study design or data acquisition or data analysis/ interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, R.K., P.S., A.D.S.; clinical studies, R.K., P.S., A.D.S.; statistical analysis, R.K., P.S., J.F.; and manuscript editing, all authors Authors stated no financial relationship to disclose. 944 Radiology: Volume 238: Number 3 March 2006

EMERGING TECHNOLOGIES IN THE BATTLE AGAINST KNEE OSTEOARTHRITIS: NEW ANSWERS TO OLD QUESTIONS

EMERGING TECHNOLOGIES IN THE BATTLE AGAINST KNEE OSTEOARTHRITIS: NEW ANSWERS TO OLD QUESTIONS Dr. Jason Peeler PhD, CAT(C) Department of Human Anatomy & Cell Science, U of M Pan Am Clinic Research Foundation