Content area
Full text
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
Osteoarthritis (OA) is a disease characterised by a gradual loss of cartilage which extends over years and decades. Primary symptoms of the disease are pain and tenderness over the joint [1]. Although OA can affect any synovial joint, OA of knee joints is the most cumbersome in terms of prevalence and disability [2, 3]. OA is an age-related disease [4]. Therefore, the number of patients suffering from it is increasing in developed countries along with the aging of those societies. In the United States, for example, the number of patients with knee OA was 43 million in 1997 and is anticipated to be more than 60 million by 2020 [5]. Therefore, there is now a mounting demand for effective treatments for the disease. Considering the number and age of the patients with knee OA, such treatments should be safe and economically affordable.
Hyaluronic acid (HA) is a mucopolysaccharide comprised of tandem repeats of D-glucuronic acid and N-acetyl glucosamine. It is abundantly present in the synovial fluid [6]. At present, intra-articular administration of HA is the treatment of choice for patients with symptomatic knee OA [7]. Compared with steroids, HA placed into joints may work more slowly, but its effect may last considerably longer [8]. According to the current protocol, HA should be administered repeatedly into the joint cavity [9]. This necessity for multiple injections is a major drawback of the therapy. To be treated with HA, patients must visit clinics repeatedly and must undergo the discomfort associated with the injections. Again, the risk of complication increases by the repetition of injections [10]. Considering these overt and potential disadvantages, it is far more desirable for the symptoms of knee OA to be relieved by oral administration of HA.
Previous studies have suggested that the symptoms of knee OA might indeed be alleviated by HA ingestion [11–14]. When knee OA patients were treated with 240 mg of HA per day for 12 weeks, both the Japanese Knee Osteoarthritis Measure (JKOM) score and the Japan Orthopaedic Association (JOA) score improved significantly from levels before the treatment [11]....