The numbers speak for themselves

Osteoarthritis is the leading cause of disability in the general population of the United States.^1,2 The Centers for Disease Control confirms that approximately 1 in 3 adults with arthritis reported limitation in their usual activities. Arthritis of the knee alone afflicts more than 4 million people, and research shows 14 percent of individuals interviewed within the age group of 40 to 79 described knee pain with disability on most days of the previous month.³ Because of the increase in life expectancy within most societies of the western world, the high prevalence of OA is expected to increase further in upcoming years. For example, the number of first-time total knee replacements (TKR) is expected to skyrocket 673 percent to 3.48 billion by 2030.⁵

Osteoarthritis is also associated with extensive direct and indirect costs and represents a considerable burden for the healthcare system and society as a whole. In the United States, the cost of medical care and lost productivity is estimated at $86.2 billion. In the year 2000, hospital costs in the United States for TKR surgery topped $11 billion.^5,6 Beyond this condition’s economic burden, arthritis affects the quality of life for those afflicted and is associated with disabling one’s activities of daily living. Physical therapy is among the treatment options for people who suffer from osteoarthritis and intends to prevent physical impairment and restore functional ability through the use of exercise, physical modalities, and patient education. Current evidence supports the effectiveness and safety of moderate- to high-intensity aerobic and strengthening exercises for osteoarthritis. It is important to note that participation in recreational activities does not replace the need for therapeutic exercises.

It’s in the joints

OA is a degenerative condition that affects subchondral bone, joint synovium, tendons, ligaments, muscles, and particularly large weight-bearing joints. The affected cartilage initially develops small tears at the articular surface, which eventually results in larger tears. The cartilage eventually fragments off into joints with cartilage-forming cells called chondrocytes replicating in an attempt to keep up with the cartilage loss. Over time, these cells eventually are unable to produce at the rate of degeneration and the underlying bone becomes exposed.

Risk factors associated with knee OA are genetic predisposition, obesity (i.e., body mass index > 30 kg/m2), advancing age, and physically demanding occupations.³ OA is particularly common in older patients, but can occur in the younger population either through genetics or, more commonly, because of previous joint trauma. Symptoms of OA include pain during and/or after use, joint stiffness, swelling, crepitus, and loss of motion.

Several methods exist that can help diagnose knee and other forms of OA. The Kellgren and Lawrence System is the most universally accepted method for classifying degrees of OA and is based on radiographic findings.⁷ The Kellgren and Lawrence System uses four radiographic features: joint space narrowing, osteophytes, subchondral sclerosis, and subchondral cysts. Another method of staging called the Outerbridge method classifies articular cartilage damage based on the arthroscopic findings in patients affected with OA. The four grades are:

• Grade I — Softening and swelling
• Grade II — Fragmentation and fissuring < 0.5 inches
• Grade III — Fragmentation and fissuring > 0.5 inches
• Grade IV — Erosion down to the subchondral bone

The American College of Rheumatology recommends a combination of history, physical examination, and laboratory tests as the three methods to help diagnose OA of the knee.⁸ However, simple clinical criteria diagnose OA of the knee with a sensitivity of 89 percent and a specificity of 88 percent.^8,9 (See sidebar.)