Health Bulletin - Oct 1, 2015

Osteoarthritis (OA) is a disabling degenerative joint disease leading to joint pain, stiffness and loss of function predominantly in the knees, hips, hands, spine and other weight-bearing joints. Osteoarthritis is incurable and at present most treatments are only able to provide symptomatic relief. In this article, causes of the disease, treatment options and preventive measures are reviewed.

Chronic knee pain and preventive measures
Arthritis is inflammation of joints. Pain, swelling, and stiffness are the primary symptoms of arthritis. Any joint in the body may be affected by the disease, but it is particularly common in the knee. Knee arthritis is one of the most common forms of musculo-skeletal disease encountered in all countries of the globe. In Europe, a joint is replaced due to OA every 1.5 minutes [1]. The situation is even worse in the U.S., where a total of ~719,000 joint replacements are performed in 2010 [2]. According to the Arthritis Foundation, more than 27 million people in the U.S. have osteoarthritis.

Brief anatomy of knee
The knee is the largest joint in the body (Fig 1). The knee is made up of the lower end of the thighbone (femur), the upper end of the shinbone (tibia), and the kneecap (patella). The ends of these three bones where they touch are covered with articular cartilage, a smooth substance that protects the bones and enables them to move easily. The menisci are located between the femur and tibia. These C-shaped wedges act as "shock absorbers" that cushion the joint. Large ligaments hold the femur and tibia together and provide stability. The long thigh muscles give the knee strength. All remaining surfaces of the knee are covered by a thin lining called the synovial membrane. This membrane releases a fluid that lubricates the cartilage, reducing friction to nearly zero in a healthy knee. Normally, all of these components work in harmony. But disease or injury can disrupt this harmony, resulting in pain, muscle weakness and reduced function [2].

Figure 1. (A) Common target sites for osteoarthritis [1]. The most common target joint affected is the knee joint, whereas hip, shoulder, spine and toe are less frequently affected. Osteoarthritis has a slow, insidious onset and mostly affects only one or a few joints (in contrast to rheumatoid arthritis, which is a systemic multi-joint disease). (B) Normal knee anatomy. (C) Osteoarthritis often results in bone rubbing on bone. Bone spurs are a common feature of this form of arthritis [3].

Cause of chronic knee pain
Osteoarthritis is the most common form of arthritis in the knee. It is a degenerative,"wear-and-tear" type of arthritis that occurs most often in people 50 years of age and older, but may occur in younger people, too. In osteoarthritis, the cartilage in the knee joint gradually wears away. As the cartilage wears away, it becomes frayed and rough, and the protective space between the bones decreases. This can result in bone rubbing on bone, and produce painful bone spurs (Fig 1). Osteoarthritis develops slowly and the pain it causes worsens over time.

Rheumatoid arthritis is a chronic disease that attacks multiple joints throughout the body, including the knee joint. It is symmetrical, meaning that it usually affects the same joint on both sides of the body. In rheumatoid arthritis the synovial membrane that covers the knee joint begins to swell. This results in knee pain and stiffness. Rheumatoid arthritis is an autoimmune disease. This means that the immune system attacks its own tissues. The immune system damages normal tissue (such as cartilage and ligaments) and softens the bone. Post-traumatic arthritis is form of arthritis that develops after an injury to the knee. For example, a broken bone may damage the joint surface and lead to arthritis years after the injury. Meniscal tears and ligament injuries can cause instability and additional wear on the knee joint, which over time can result in arthritis.

Osteoarthritis of the knee is more common in women and older people. Systemic and local risk factors have been identified (Fig 2), with obesity and joint injury being important modifiable factors [4]. This latter risk factor means that a proportion of those affected will be young active people in their 30s and 40s. Therefore, strategies targeted towards weight reduction and prevention of knee injuries could prevent large numbers of people developing the condition.

Diagnosis
Clinically, osteoarthritis is diagnosed on the basis of a history and physical examination. Symptoms suggestive of OA of knee include persistent knee pain, knee stiffness and reduced function. Some of the signs include restricted movement and bony enlargement. X-ray imaging of an arthritic knee may show a narrowing of the joint space or changes in the bone. Occasionally, an MRI scan, a CT scan, or a bone scan may be needed to determine the condition of the bone and soft tissues of the knee [4].

Treatment options and preventive measures
There is no cure for arthritis but there are a number of treatments that may help relieve the pain and disability it can cause. Initial treatment of arthritis of the knee is nonsurgical such as changes in lifestyle and physiotherapy. Minimizing activities that aggravate the conditions (for example, switching from high impact activities like jogging or tennis to lower impact activities like swimming or cycling) may help to slow the progress of arthritis. Increasing body weight leads to a linear increase in joint loading. Therefore, losing weight can reduce stress on the knee joint, resulting in less pain and increased function. Specific exercises can help increase range of motion and flexibility, as well as help strengthen the muscles in the leg. Various analgesics and anti-inflammatory agents may be used for the management of pain and inflammation [3].

Alternative treatment options such as plant extracts [5] and acupuncture [6] have proven to be effective in multiple randomized clinical trials and may be helpful to try. Low vitamin-D levels are reported to be associated with osteoarthritis. It also has been shown that capacity of human skin to produce vitamin D decreases in old age. Therefore, it is beneficial to maintain optimal levels of vitamin D (>20 ng/mL) using supplements [7]. Surgical treatment is the last option recommended for the uncontrolled joint pain. Type of the surgery depends on the tissue of the joint damaged (bone, cartilage etc.). In a total or partial knee replacement (arthroplasty), the damaged cartilage and bone will be removed, and then new metal or plastic joint surfaces are positioned to restore the function of the knee. More than 90% of people who have total knee replacement surgery experience a dramatic reduction of knee pain and a significant improvement in the ability to perform common activities of daily living [3].

References:

[1] Wieland HA et al. (2005) Osteoarthritis - an untreatable disease? Nature Reviews, Drug Discovery 4:331
[2] http://www.cdc.gov/nchs/fastats/inpatient-surgery.htm
[3] http://orthoinfo.aaos.org/topic.cfm?topic=a00389
[4] Bennell KL et al. (2012) Management of osteoarthritis of the knee BMJ 345:e4934
[5] Walzer SM et al. (2015) Medical Plant Extracts for Treating Knee Osteoarthritis:a Snapshot of Recent Clinical Trials and TheirBiological Background. CurrRheumatol Rep 17: 54
[6] Selfe TK and Taylor AG (2008) Acupuncture and Osteoarthritis of the Knee:A Review of Randomized, Controlled Trials. Fam Community Health 31(3): 247-254
[7] Mabey T and Honsawek S (2015) Role of Vitamin D in Osteoarthritis: Molecular, Cellular,and Clinical Perspectives. International Journal of Endocrinology, Article ID 383918

Contributors

Vijay Gangula
Chair, Health Committee
Vijay.gangula@gmail.com

Advisory Committee:
Surender Reddy Neravetla M.D., FACS