Kari Senica, M.D.
Board Certified Orthopedic Surgeon
Osteoarthritis, also called degenerative or “wear and tear arthritis”, is the most common type of arthritis in the knee. Osteoarthritis is the leading cause of disability in the United States. It is estimated that it affects 13.9% of adults age 25 and older and 33.6% of adults over 65 years of age. As estimated 27 million adults have been diagnosed with osteoarthritis in 2005. www.cdc.gov/arthritis/data/statistics
Osteoarthritis involves the destruction and breakdown of articular cartilage. Cartilage protects the underlying bone at the joint surfaces and acts as a shock absorber. It provides a smooth, frictionless surface for movement. Osteoarthritis also affects the other structures in the knee, including the synovium (lining of the knee joint, ligaments and bone.)
Risk factors for osteoarthritis of the knee include advancing age, gender (women are more at risk for developing OA than men) and family history. Previous trauma to the knee joint can also increase osteoarthritis, including anterior cruciate ligament tears (ACL or meniscal tears.) Injury to the knee joint when it did not require surgical treatment may still increase the risk of osteoarthritis. Obesity also increases the risk of knee osteoarthritis.
Symptoms of knee arthritis include pain, swelling, stiffness and decreased range of motion. Some patients may describe a “feeling of giving way” or a crunching or cracking noise with walking or stair climbing. In the early stages of osteoarthritis, pain may be more intermittent and noticed only with overuse. In the later stages of disease, it may cause pain even at rest or at night.
The diagnosis of osteoarthritis is usually made based on the patient’s history and physical examination findings. X-rays usually confirm a diagnosis of osteoarthritis. In the early stages of disease, there may not be any significant radiographic findings. Special x-rays in which the patient is upright (standing or standing with the knees bent 45 degrees) are more sensitive for earlier identification of OA. A supine or film taken with the patient lying down without weight on the leg may not show changes of osteoarthritis. Classic findings on x-rays include joint space narrowing, bone spurs (osteophytes), and sclerosis (increased density of bone or bone cysts.) MRI is not routinely needed to diagnose osteoarthritis, but can identify other causes of joint pain, such as osteonecrosis or stress fracture. Meniscal tears are seen very commonly in patients with osteoarthritis and are not necessarily the cause of their symptoms.
There is currently no cure for osteoarthritis or therapies to prevent disease progression. Treatment of OA focuses on decreasing pain and swelling and improving function. Treatment usually begins with nonsurgical management. This includes physical therapy, exercise and weight loss. Many patients have quadricep muscle weakness and increasing muscle strength helps reduce the load on cartilage.
Physical therapy also works to improve range of motion. Low impact exercises, also prescribed, have shown to improve symptoms and increase function. Running increases compressive loads at the knee joint by 33 x body weight in comparison to level walking (3.5 x body weight) or cycling (1.2 x body weight.) In older patients, using an assistive device, such as a cane or walker, may be very beneficial. Aquatic therapy is also beneficial, because exercise in waist-deep water decreases weightbearing forces at the knee by 50%. Weight loss is strongly encouraged because each pound of weight loss results in a fourfold reduction in load exerted on the knee per step during activities of daily living.
Medication can also be used for treatment of osteoarthritis. A simple analgesic, such as acetaminophen, is tried initially. Nonsteroidal anti-inflammatories, such as Aleve or Advil over-the- counter or prescription NSAIDs also are very beneficial, but must be used with caution in patients with cardiac or gastrointestinal problems. Oral glucosamine and chondroitin have been shown to reduce pain in some patients and need to be taken for at least two months to see an improvement in symptoms. Knee bracing, both over-the-counter and custom off-loading braces, may provide symptom relief in some patients. There are two major types of knee injections that can be administered for patients with knee osteoarthritis. Intraarticular corticosteroid injections are beneficial to reduce pain and swelling, but have to be used in a limited fashion and usually provide only short-term benefit.
Viscosupplementation is another type of intraarticular injection which can improve knee symptoms. There are various name brands, including Hyalgan, Supartz, Euflexxa and Synvisc. Sometimes these are referred to as” rooster comb shots “and are usually administered one time a week for three weeks to provide shock absorption and lubrication in the joint. Newer preparations can be administered in a single injection fashion and can be repeated in six months if the patient has shown improvement in symptoms.
Surgical treatments for osteoarthritis of the knee include arthroscopic debridement, osteotomy or joint arthroplasty. Osteotomy is used in younger patients to improve alignment of the knee and involves cutting and realigning the bone. Joint arthroplasty may include unicompartmental or partial knee replacement, total knee arthroplasty or isolated patellofemoral arthroplasty, depending on patient age,and degree and location of arthritis. Treatment decisions need to be individualized for each patient based on the effectiveness and the tolerability of the various modalities.