Practical Overview of Osteoarthritis
Osteoarthritis (OA) is a common cause of pain and disability in adults. Approximately 27 million Americans have clinical OA, which translates to nearly 14% of those over age 25 and 33% of those over 65 years of age.1 OA is a disease of the entire joint involving the cartilage, joint lining, ligaments, and underlying bone.2 The breakdown of these tissues eventually leads to pain and joint stiffness. The joints most commonly affected are the knees, hips, and those in the hands (Table 1).3
The specific causes of OA are unknown but it is believed to result from both mechanical (overuse and wear and tear) and molecular events in the affected joint. Recent studies linked an increased risk of OA with higher levels of C-reactive protein and erythrocyte sedimentation rate, as well as higher prevalence of metabolic syndrome4
There is a highly heritable component associated with OA.5,6 In fact, there is a genetic contribution to OA for 60% of women.7 Among the genes that have been linked to OA are several that are involved in the development and maintenance of joint shape, including members of the Wingless and bone morphogenetic protein families. Important genetic markers for the development and progression of the disease are under research.7
OA impacts quality of life and increases health-related expenditures. For example, OA of the knee is one of the 5 leading causes of disability among non-institutionalized adults.8 About 80% of patients with OA have some degree of movement limitation and 25% cannot perform major activities of daily living; 11% of adults with knee OA need help with personal care and 14% require help with routine needs. About 40% of adults with knee OA report their health as “poor” or “fair.”8
According to the Centers for Disease Control and Prevention, OA costs $3.4 to $13 billion per year.9 The average direct cost of OA per patient is $2,600 per year,10 and the total annual cost is $5,700 per person.11
Treatment for OA focuses on relieving symptoms and improving function, and can include a combination of patient education, physical therapy, weight control, medications, and, perhaps eventually, total joint replacement. Hospital expenditures for total knee and hip joint replacements in 2009 were estimated to be $28.5 billion and $13.7 billion, respectively.12
This article aims to review the suspected causes and risk factors for OA (Table 2)4-6,9,13 and its symptoms, and to outline the appropriate diagnostic approach for the various types of OA.
Spinal OA (Spondylosis)
Spinal OA, or spondylosis, can occur anywhere along the spine, but most commonly affects the cervical spine (neck) and lumbar spine (low back).14 Like other types of OA, spondylosis is a degenerative disorder. In the normal spine, the vertebrae and cartilage, which cushions the bones as they move, are healthy and in alignment. Every vertebra has two sets of joints called facet joints that help facilitate movement.
Through use (and especially through overuse), cartilage can start to wear down, affecting movement and causing pain. When the cartilage on the facet joints starts to wear down, the bones can start to rub together. In an effort to stop this painful movement, the bones may create bone spurs. This is the body’s attempt to stabilize the joint, but unfortunately, these bone spurs can make movement more difficult. They also can pinch nerves in the spine, causing more pain.
As patients grow older,9 the discs between the vertebrae that cushion the spine’s movement and help it bend and twist can start to wear out—this is called degenerative disc disease. It is a separate spinal condition from spondylosis, but they are closely linked. If, for example, a disc between the vertebrae starts to thin, it can change the way facet joints work—causing the cartilage to wear out and leading to spondylosis. In addition to age, other risk factors that can contribute to degeneration include:
- Occupations that excessively strain the spine
- Past neck or spine injury
- Ruptured or slipped disc
- Being overweight and not exercising (Note: the literature is undecided on this point, but it is important to encourage patients to lose weight and exercise)
- Small fractures to the spine caused by osteoporosis
- A family history of spondylosis
Symptoms of spondylosis tend to come on gradually as the spine changes. Patients may notice that movement has become more difficult or painful. Patients may feel “stiff,” especially in the morning or after sitting for a while. If a bone spur is pressing on a nerve, the patient may have pain that travels away from the spine. For example, if a bone spur is pinching a nerve in the neck, pain may radiate down the arm. Symptom of spondylosis in the neck include:
- Neck pain and stiffness, which may get worse with activity
- Weakness and numbness in the arms, hands and fingers
- Muscle spasms in neck and shoulders
- Grinding and popping sound/feeling in the neck when you move
The hand is one of the parts of the body most frequently affected by OA.15 OA can occur in many areas of the hand and wrist. In a healthy hand, a joint is made of 2 smooth bone surfaces covered in cartilage, a slippery tissue that provides a smooth gliding surface and allows the bone surfaces to fit well together. If the cartilage wears away, the sensitive underlying bone can become exposed. The result is bone-on-bone contact, which leads to pain, stiffness, and difficulty using the hand.
OA of the hand is most likely to develop between the ages of 40 and 70. In people under 40, OA of the hand is usually caused by an injury to the affected joint. For most people, however, the most significant risk factor is age. Other risk factors include having a job or hobby that involves repeated hand motions, being female,13 having a family history of hand OA, and obesity.
The 3 most frequent sites of OA of the hand include:
- The base of the thumb, where the thumb and wrist come together
- The joint closest to the fingertip
- At the middle joint of a finger
An early symptom of hand OA is joint pain. It may produce a burning or a dull sensation. A person often feels the pain after heavy gripping or grasping. The pain may occur hours later, or even the next day. In advanced stages, the pain may wake a person up. Other symptoms include: