Journal of Orthopedics & Rheumatology
A Systematic Approach to Evaluating Knee Radiographs with a Focus on Osteoarthritis
Christopher M Melnic*, Joshua Gordon, P Maxwell Courtney, and Neil P Sheth
- University of Pennsylvania, Department of Orthopaedic Surgery Hospital of the University of Pennsylvania, USA
*Address for Correspondence: Christopher M Melnic, Hospital of the University of Pennsylvania, Department of Orthopaedic Surgery, 3400 Spruce Street, 2 Silverstein Philadelphia, PA 19104, USA, Tel: 610-751-3986; E-mail: Christopher.Melnic@uphs.upenn.edu
Citation: Melnic CM, Gordon J, Courtney PM, Sheth NP. A Systematic Approach to Evaluating Knee Radiographs with a Focus on Osteoarthritis. J Orthopedics Rheumatol. 2014;1(2): 6.
Copyright © 2014 Melnic CM, et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use,distribution, and reproduction in any medium, provided the original work is properly cited.
Journal of Orthopedics & Rheumatology |ISSN: 2334-2846 | Volume: 1, Issue: 2
Submission: 25 December 2013 | Accepted: 29 January 2014 | Published: 06 February 2014
Reviewed & Approved by: Dr. Jun Li Division of Clinical Immunology & Rheumatology, University of Alabama at Birmingham, USA
AbstractArthritis of the knee is commonly encountered in primary care and specialty settings. The initial work up and treatment of these patients requires a thorough evaluation and complete series of plain radiographs. Despite increased use of advanced imaging modalities, plain films remain the most instructive, available, and affordable diagnostic test. The evaluation of patients with arthritis can be challenging, by using a standardized approach one can perform a quick and adequately comprehensive evaluation. Here we outline an approach appropriate for the evaluation of these patients in any setting. Particularly, we advocate a complete history and physical exam augmented by a four view radiographic series: A weight bearing anterior-posterior (AP) of the knee, a 45 degree weight bearing posterior-anterior (PA) view of the knee, a standing lateral, and a Merchant view. Through our described systematic evaluation of these views, a great deal of information can be obtained often helping guide treatment plans created with the patient, and helping avoid a potential missed or delayed diagnosis.
BackgroundOsteoarthritis (OA) is the most common form of arthritis, and the knee is the principal large joint affected by this process . In men and women over the age of fifty-five, an estimated ten percent develop disabling knee pain from OA; 25% of those affected are considered severely disabled . The incidence of osteoarthritis of the knee increases with age, is strongly associated with obesity , and more commonly affects women . OA is the single greatest contributor to disability [5,6], and in the elderly, its overall risk of disability is comparable to that of cardiovascular disease. The precise etiology, pathogenesis, and progression of OA are not yet completely understood.
Systematic Approach to the Arthritic KneeIn the evaluation of the adult patient with degenerative joint disease of the knee, we suggest a systematic approach (Figure 1). Each patient should receive a thorough history and physical examination. Imaging by means of plain radiographs is valuable as a confirmatory test, but has been proven to be less sensitive and specific than clinical assessment by a physician . There is often a disparity between clinical and radiographic severity of disease, and in most circumstances, radiographs do not provide a good metric by which to measure the likelihood of progression [11-13]. Although it is important to be aware of these limitations, radiographs remain the gold standard imaging modality [11,14,15]. Magnetic Resonance imaging (MRI) and other imaging modalities may prove useful but are often impractical and costly with limited availability in many settings. MRI should never be used as an initial evaluation tool for the painful knee. Weight bearing radiographs provide far more clinical information about the functional joint space than a non-weight bearing MRI performed in the supine position. Furthermore, these advanced imaging modalities infrequently supplement a standard radiographic series in patients with moderate to severe degenerative joint disease.
Radiographic Hallmarks of other Joint DiseasesEvaluation of secondary arthritis requires the same four radiographs. The underlying etiology can often be heralded by key radiographic features, which can help differentiate knee pain caused by secondary conditions. Here we outline some of the common causes of secondary arthritis and the radiographic features useful in diagnosis.
Joint destruction associated with hemophilia is also seen at a young age. Numerous intra-articular hemorrhages throughout a hemophiliac patient’s life may result in articular cartilage damage yielding chronic synovitis causing further joint destruction. Radiographic analysis typically demonstrates flattening of the distal femoral condyles, enlargement and widening of the epiphysis, trabecular accentuation, widening of the intercondylar notch, and squaring of the inferior margin of the patella . The thickened synovium that results from this chronic process leads to marginal erosions and subarticular cyst formation. Joint effusion is typically encountered in the setting of an acute hemarthrosis.
The knee is the most common joint affected by calcium pyrophosphate dihydrate (CPPD) deposition disease. The diagnosis is most commonly confirmed by knee joint aspiration, demonstrating the presence of rhomboid shaped crystals in the synovial fluid that are positively birefringent under a polarizing microscope. CPPD crystals are deposited in the articular cartilage resulting in chondrocalcinosis, and the fibrocartilagenous structures of the knee become calcified and can become evident radiographically. Calcification of the menisci is usually seen, and the lateral meniscus is most commonly involved. On the lateral radiograph, calcification of the gastrocnemius tendon may also be appreciated . Degenerative changes in CPPD affect the patellofemoral joint more frequently than the other compartments (Figures 8 and 9) .
ConclusionOur systematic approach outlines a method for evaluating the patient with knee pain and suspected osteoarthritis. As such a prevalent condition, and one seen by nearly all medical specialties, our system provides a helpful guide regarding which radiographs to order, the correct technique to obtain to proper radiographic projections, what key features to evaluate on each view, and in general terms when to refer to a specialist. Initial radiographs should include four views: a (1) weight bearing AP, a (2) weight bearing 45 degree PA, a (3) standing lateral, and a (4) Merchant view. Each radiograph should first be evaluated for quality and then for pathology. An analysis, performed in a stepwise fashion (Figure 1), allows the treating physician to fully assess the radiographs of the osteoarthritic knee in a reproducible fashion.
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