Clinical and radiological features of knee osteoarthritis in patients attending the university hospital of Kinshasa, Democratic Republic of Congo

Introduction The aim of the present study was to describe the clinical and radiological features of knee osteoarthritis in Congolese outpatients attending the University Hospital of Kinshasa (UHK). Methods A cross-sectional study was performed in the rheumatology unit of the UHK from January to August 2012. Patients were consecutively recruited. The diagnosis of Osteoarthritis (OA) was based on the criteria of the American College for Rheumatology. Demographic, clinical and x-rays data were collected. The X-rays severity was assessed according to Kellgren and Lawrence's method. Results 1049 patients attended the Rheumatology unit of the UHK during the study period. An accurate diagnosis was reported for 839 patients, of whom 376 (44.8%) suffered from OA. Knee OA was diagnosed in 118 patients (31.4% of all OA patients). 101 patients accepted to be included in the study, 78 women (77.2%) and 23 men (22.8%). Their average age was 58.9 ± 10 years. A body mass index (BMI) ≥ 25kg/m2 was observed in 68 patients of whom 28 were obese (BMI ≥ 30kg/m2). The main symptoms were a mechanical pain (100%), swelling (40.6%), crepitus (79.2%) and mobility reduction (X%). Knee deformities were observed in some patients. At baseline, radiological damages > stage 2 of Kellgren-Lawrence were found in 70 patients. Conclusion Knee OA is a common disease among outpatients who attend the unit of Rheumatology of the UHK. Its clinical profile is the same as what is reported in the literature. Obesity and skeletal abnormalities are encountered in the majority of patients.


Introduction
Osteoarthritis (OA) is the most common joint disease but it remains one of the least studied rheumatic diseases in Africa [1]. Knee OA affects a large number of people, especially among people of 50 years and over. Its progression is slow and irreversible, and often leads to serious disability problems. In 1986, the American College of Rheumatology (ACR) proposed criteria for the diagnosis of the knee OA [1]. But there is no international agreement on the criteria to be used in epidemiological and clinical studies or on methods of monitoring OA patients [2]. The prevalence of knee OA in different studies depends on diagnostic criteria (clinical or radiological) and on the characteristics of the studied populations [3]. Knee OA concerned 2.9% of women aged between 45 and 65 years in the Chingford Study [4]. In the Framingham study (US), this prevalence was 6.1% in adults patients aged more than 30 years and 9.5% in old people [5]. In France, the prevalence of symptomatic knee OA is approximately 9% of people over 40 years [6].
In sub-Saharan Africa, some hospitalized based studies have been conducted on knee OA [7][8][9][10][11][12][13][14]. Ouédraogo [13,14]. With the aging population and the increasing prevalence of obesity, the number of people suffering from OA is expected to grow over next decades. This disease is an important public health problem and is of interest for researchers in rheumatology, taking into account its functional disorder and impact [15,16]. The objective of the present study was to describe the clinical and radiological profile of knee OA in Congolese patients attending the UHK.

Methods
A cross-sectional study was conducted in outpatients who attended the rheumatology unit of the UHK during the period from 3 January

Results
One thousand and forty-nine (1049) patients attended the  Figure 1. This figure shows that more than 70% of patients were at least stage III. Table 4 shows the locations of the knee X-rays lesions in the present study. We note that patellofemoral involvement was the most frequent. Table   5 indicates that there was no association between the pain intensity at inclusion and the stage of X-rays abnormalities, with a variance ratio of 1.74 and a p-value of 0.2.

Discussion
The aim of the present study was to describe clinical and radiological Overweight and skeletal deformities were also involved in the onset of the disease. The high frequency of OA is in agreement with published data which show that OA is the most common [1,17] rheumatic disease. The knee OA is very common in Congolese patients as reported in previous studies by Bwanahali et al. [13] and by Malemba and Mbuyi-Muamba [14]. A high incidence of knee OA was also observed in Arab people [18]. Genetic factors may play a role in the location of OA [19,20]. Some studies conducted in multiracial areas such as USA and Hong-Kong supported the possible role of genetic factors. For example, fingers and hip OA are common in whites but rare in blacks [19,20]. It is clear that the finger joints are most commonly used in daily activities in all populations and races. Therefore the main reason for the extreme rarity of fingers OA in blacks would be genetic. The role of genetics has also been reported by a British study of twins suffering from OA. It concluded that the influence of genetic intervened to 39-74% (depending on location) in the pathogenesis of OA [21]. Chitnavis in the USA described a lot of cases of familial knee OA [22]. Environmental factors such as obesity and daily activities are also involved in the frequency of knee OA. The role of obesity in the development of knee OA is well known [23,24]. In the present study, overweight and obesity were observed in 68% and 28% of patients respectively.
These conditions may aggravate OA because knees participate in supporting the body weight. Many studies have demonstrated a significant relationship between BMI and the risk of developing the knee OA [13,25,26]. Each kg/m 2 in excess over a BMI of 27 kg/m 2 increases the risk by 15%. The average age of patients in this study was 58.9 ± 10.0 years. It's known that advanced age is a risk factor for OA [6,7]. Looser et al. [26] postulated that factors such as age-related alteration of cell and tissue function, sarcopenia, loss of proprioception and increased ligament laxity, combined with other factors such as obesity, traumatism and genetic factors lead to the occurrence of OA. The predominance of the female sex observed in the present study was also reported in several studies [6-8, 15, 16, 27-30]. The high frequency of obesity in women and menopause may play a role in this female predominance. Two studies performed in West Africa also observed that obesity was more common in females than males [7,8]. In addition to that postmenopausal statue may be as a potential risk factor for OA, but and the stage of X-ray abnormalities shows the discrepancy which may exist between the OA symptoms and its X-rays profile.

Conclusion
Knee OA is a common disease in the service of Rheumatology of the  This study shows that Congolese health system must be improved, so that patients can consult physicians a bit earlier.

Competing interests
The authors declare no competing interests.

Authors' contributions
Adolphe Lukusa has a substantial contribution to conception,