Osteoarthritis- Clinical Presentation
By Shari M. Ling, M.D. and Joan M. Bathon, M.D.
- Epidemiology
- Signs and Symptoms of OA
- Differential Diagnosis
- Are There Biological Markers for OA?
- References
Osteoarthritis (OA) is the most prevalent type of arthritis, particularly in adults 65 years and older. OA is a chronic degenerative arthropathy that frequently leads to chronic pain and disability. With the aging of our population, this condition is becoming increasing prevalent and its treatment increasingly financially burdensome. Finding better treatments for OA is a major focus of research at this time.
OA is the most common type of arthritis. Reported incidence and prevalence rates of OA in specific joints vary widely, due to differences in the case definition of OA (slide). OA may be defined by radiographic criteria alone (radiographic OA), by typical symptoms (symptomatic OA), or by both. Using radiographic criteria, the distal and proximal interphalangeal joints of the hand have been identified as the joints most commonly affected by OA, but they are the least likely to be symptomatic. In contrast, the knee and hip, which constitute the second and third most common locations of radiographic OA, respectively, are nearly always symptomatic. The first metatarsal phalangeal and carpometacarpal joints are also frequent sites of radiographic OA, while the shoulder, elbow, wrist and metacarpophalangeal joints rarely develop idiopathic OA.
What are the risk factors for developing OA? (slide)
In demographic studies, age is the most consistently identified risk factor for OA, regardless of the joint being studied. Prevalence rates for both radiographic OA and, to a lesser extent, symptomatic OA rise steeply after age 50 in men and age 40 in women.
Female gender is also a well-recognized risk factor for OA. Hand OA is particularly prevalent among women. In addition, polyarticular OA and isolated knee OA are slightly more common in women than men, while hip OA occurs more commonly in men. Interestingly, women are more likely to report pain in all affected joints, including the hip, than men.
Cohort studies have demonstrated a clear association of obesity with the development of radiographic knee OA in women and a weaker association with hip OA. Whether obesity is a risk factor for the development of hand OA remains controversial. (more info on OA and Body Weight)
Occupation-related repetitive injury and physical trauma contribute to the development of secondary (non-idiopathic) OA, sometimes occurring in joints that are not affected by primary (idiopathic) OA, such as the metacarpophalangeal joints, wrists and ankles. Although the prevalence of knee OA is greater in adults who have engaged in occupations that require repetitive bending and strenuous activities, an association with regular, intense exercise remains controversial. While early studies in joggers failed to find a higher prevalence of OA of the knee in joggers compared to non-joggers, a recent study of the Framingham data base in elderly adults provided the first longitudinal association between high level of physical activity and incident knee OA. Low-impact and recreational exercises are unlikely to constitute a risk factor for knee OA, and are likely to benefit the cardiovascular system. Prior menisectomy is a significant risk factor in men for the development of OA in the knee.
OA is diagnosed by a triad of typical symptoms, physical findings and radiographic changes. The American College of Rheumatology has set forth classification criteria to aid in the identification of patients with symptomatic OA that include, but do not rely solely on, radiographic findings. (ACR Guidelines-Clinical Classification criteria for OA of the Hip) (ACR Guidelines-Clinical Classification criteria for OA of the knee) Patients with early disease experience localized joint pain that worsens with activity and is relieved by rest, while those with severe disease may have pain at rest. Weight bearing joints may "lock" or "give way" due to internal derangement that is a consequence of advanced disease. Stiffness in the morning or following inactivity ("gel phenomenon") rarely exceeds 30 minutes.
Physical findings in osteoarthritic joints include bony enlargement, crepitus, cool effusions, and decreased range of motion (slide). Tenderness on palpation at the joint line and pain on passive motion are also common, although not unique to OA. Radiographic findings in OA (slide) include osteophyte formation, joint space narrowing, subchondral sclerosis and cysts. The presence of an osteophyte is the most specific radiographic marker for OA (ACR Guidelines-Clinical Classification criteria for OA of the knee) although it is indicative of relatively advanced disease.
If a patient has the typical symptoms and radiographic features described above, the diagnosis of OA is relative straightforward and is unlikely to be confused with other entities. However, in less straightforward cases, other diagnoses should be considered. For example, periarticular pain that is not reproduced by passive motion or palpation of the joint should suggest an alternate etiology such as bursitis, tendonitis or periostitis. If the distribution of painful joints includes MCP, wrist, elbow, ankle or shoulder, OA is unlikely. Prolonged stiffness (greater than one hour) should raise suspicion for an inflammatory arthritis such as rheumatoid arthritis. Marked warmth and erythema in a joint suggests an infectious or microcrystalline etiology. Weight loss, fatigue, fever and loss of appetite suggest a systemic illness such as polymyalgia rheumatica, rheumatoid arthritis, lupus or sepsis or malignancy.
Are There Biological Markers for OA?
Radiographs are considered the "gold standard" test for the diagnosis of OA, but radiographic changes are evident only relatively late in the disease. The need is great for a sensitive and specific biological marker that would enable early diagnosis of OA, and monitoring of its progression. Routine laboratory studies, such as sedimentation rates and c-reactive protein, are not useful as markers for OA, although a recent study suggests that elevation of CRP predicts more rapidly progressive disease.
Several epitopes of cartilage components, however, have been described that offer some promise as markers of OA (slide). For example, chondroitin sulfate epitope 846, normally expressed only in fetal and neonatal cartilage, has been observed in OA, but not normal adult, cartilage and synovial fluid. Along a similar vein, an epitope unique to type II collagen has been described in OA cartilage, and can be unmasked in vitro by exposing normal cartilage to MMPs. This epitope can be measured in blood and urine and may prove useful in diagnosing or monitoring OA progression. Elevated serum hyaluronan levels have also been shown by some to correlate with radiographic OA. The finding of elevated cartilage oligomeric protein (COMP) levels in synovial fluid after traumatic joint injury may portend development of OA in the injured joint. Other potential markers of OA are listed but are either not easily accessible or lack the sensitivity and specificity required to consider them as potential OA markers.
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