From the Guidelines
Knee pain is most commonly caused by degenerative knee disease, which includes conditions such as osteoarthritis, meniscus tears, and mechanical symptoms, especially in individuals over 35 years old. According to the study by 1, degenerative knee disease is an inclusive term that encompasses patients with knee pain, with or without imaging evidence of osteoarthritis, meniscus tears, or locking, clicking, or other mechanical symptoms. The causes of knee pain can be varied and include:
- Osteoarthritis
- Rheumatoid arthritis
- Injuries, such as ligament tears, meniscus tears, or fractures
- Overuse syndromes
- Patellofemoral pain syndrome
- Bursitis
- Tendinitis
- Gout
- Infections
As noted in the study by 1, genetic predisposition, trauma, overuse, obesity, and certain occupations increase the risk for the development of osteoarthritis of the knee. The management of knee pain depends on the underlying cause, and treatment may include rest, ice, compression, and elevation (RICE protocol), over-the-counter pain medications, physical therapy, weight management, and in some cases, surgical intervention. It is essential to evaluate the patient's symptoms, medical history, and physical examination to determine the best course of treatment. For example, a patient with moderate to severe tricompartmental degenerative changes, like the one described in the study by 1, may require total knee arthroplasty (TKA) after conservative management has failed.
From the FDA Drug Label
In patients with osteoarthritis, the therapeutic action of naproxen has been shown by a reduction in joint pain or tenderness, an increase in range of motion in knee joints, increased mobility as demonstrated by a reduction in walking time, and improvement in capacity to perform activities of daily living impaired by the disease The causes of knee pain mentioned in the drug label are:
- Osteoarthritis
- Rheumatoid arthritis 2
From the Research
Causes of Knee Pain
- Osteoarthritis (OA) is one of the most common causes of knee pain, affecting an estimated 654 million people worldwide 3
- Patellofemoral pain is another common cause, typically affecting people younger than 40 years who are physically active, with a lifetime prevalence of approximately 25% 3
- Meniscal tears also cause knee pain, affecting an estimated 12% of the adult population, and can occur following acute trauma or as a degenerative condition in patients with knee OA 3
- Other potential causes of knee pain include hip and knee injuries, which can be a diagnostic challenge for providers to determine the etiology of a patient's symptoms 4
Risk Factors for Knee Pain
- Age is a risk factor for knee OA, with 33% of individuals older than 75 years having symptomatic and radiographic knee OA 5
- Female sex, obesity, genetics, and major joint injury are also risk factors for knee OA 5
- Reduced physical activity can lead to a 20% higher age-adjusted mortality in persons with OA 5
Diagnosis of Knee Pain
- Clinical diagnosis of knee OA can be made based on activity-related knee joint pain with no or less than 30 minutes of morning stiffness (95% sensitivity; 69% specificity) 3
- Patellofemoral pain can be diagnosed based on anterior knee pain during a squat (approximately 91% sensitive and 50% specific) 3
- Meniscal tears can be diagnosed using the McMurray test (61% sensitivity; 84% specificity) and joint line tenderness (83% sensitivity; 83% specificity) 3
- Radiographic imaging is not recommended for all patients with possible knee OA, but can be useful in diagnosing hip and knee OA 5