This article provides guidelines for the clinical diagnosis of knee osteoarthritis.
By Anthony Teoli, M. Sc., pht.
Osteoarthritis (OA) is a complex, multifactorial condition that affects the entire joint. OA arises initially from maladaptive repair responses due to different mechanical, inflammatory and metabolic factors, which ultimately lead to structural deterioration and failure of the joint (1). OA is a leading cause of disability and currently affects approximately 250 million people worldwide (2). The joints most commonly affected by OA are the knee, the hip and the hands, with knee OA accounting for approximately 85% of the burden of OA worldwide (3).
Despite popular belief, a radiograph is not required for the clinical diagnosis of knee OA. In fact, a clinical diagnosis of knee OA can be made using the patient’s age, symptoms and clinical findings, with or without the addition of radiographs (4-6). Before we take a more in-depth look at three sets of clinical classification criteria for knee OA, it is important to emphasize that a clinical diagnosis can only be made by a medical doctor. Nonetheless, the following clinical classification criteria can still be particularly useful in clinical practice to inform the clinical impressions of other healthcare professionals, such as physiotherapists and physical rehabilitation therapists.
Table 1. Clinical Classification Criteria for Knee Osteoarthritis
|National Institute for Health and Care Excellence (4)||European League Against Rheumatism (EULAR) (6)||American College of Rheumatology (ACR) (4)|
|The clinical diagnosis of knee OA can be made without investigations if a person:|
|Is >40 years old and has:
1. Usage-related joint pain
2. Short-lived morning stiffness
3. Functional limitation
Has one or more of the following exam findings:
4. Joint crepitus
5. Restricted joint movement
6. Bony enlargement
|Has knee pain AND at least three of the following criteria:
Is there a “best” guideline for the clinical diagnosis of knee OA?
A recent cross-sectional study (7) compared these three sets of clinical classification criteria for knee osteoarthritis in 13,459 patients with knee symptoms or functional limitations associated with OA who were treated in primary care. The prevalence of knee OA according to the EULAR, ACR and NICE criteria were calculated in all participants and in the subgroup of patients. Their results demonstrated that 39% fulfilled all three sets of criteria, 48% fulfilled the EULAR criteria, 52% fulfilled the ACR criteria and 89% fulfilled the NICE criteria.
The authors also conducted a similar analysis in a subgroup of patients with self-reported radiographic knee OA (n=10,651 patients, 79% of the study sample). These study participants were patients who had had radiographs of their knee joint within the last 6 months and the results of their radiographs showed changed associated with OA. Their results demonstrated that 49% fulfilled the EULAR criteria, 54% fulfilled the ACR criteria and 90% fulfilled the NICE criteria.
The results of this study would suggest that the EULAR and ACR clinical classification criteria only identified approximately half of those with or without self-reported radiographic knee OA, who were treated because of symptoms or functional limitations associated with knee OA. Previous studies have found that 30-81% of patients with knee symptoms presenting to primary care, or in population-based studies, fulfill the ACR criteria (8-11). Given the EULAR and ACR criteria performed similarly in this study (7), the potential relevance of both the EULAR and ACR clinical classification criteria in the primary care setting is questionable.
In contrast, the NICE clinical classification criteria identified most patients (89-90%) with or without self-reported radiographic knee OA, suggesting that the NICE criteria would be most appropriate to identify individuals treated for knee OA in primary care (7). This is especially important, given the vast majority of patients with knee OA are managed in primary care (5). One important limitation of strictly applying the NICE clinical classification criteria is the age limit of “45 years or older”, as a significant number of individuals younger than 45 years of age are impacted by OA (12). As a result, a first step has been taken toward developing clinical classification criteria for early knee OA (13). However, these criteria are still preliminary and have not yet been validated (13).
How can these clinical classification criteria inform my clinical practice?
The NICE, EULAR and ACR clinical classification criteria for knee OA are invaluable resources for healthcare professionals treating patients with knee OA. First and foremost, these guidelines provide evidence-based criteria that can be used to inform the clinical impressions of healthcare professionals. As a result, the treating healthcare professional can feel more confident in their ability to identify key symptoms and examination findings consistent with the clinical diagnosis of knee OA. Additionally, these clinical classification criteria can help to guide the subjective and objective examination. For instance, questions regarding symptoms such as morning stiffness, activity-related joint pain and functional limitations are a crucial part of the subjective examination for patients with suspected knee OA. Similarly, joint crepitus, restricted joint movement, bony enlargement, joint tenderness and palpable warmth are key clinical findings and are important to note during the physical examination.
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