[Knee cartilage lesions and occupational load. Results of an arthroscopic study]

Numerous epidemiological studies have suggested a relationship between knee osteoarthritis and occupational load or, respectively, a kneeling or squatting position at work. Cartilage breakdown was clearly identified as the main mechanism of the osteoarthritic process. This arthroscopic study was aimed to evaluate the relationship between frequency and grade of knee cartilage damage compared with occupational load. It was hypothesised that heavy work conditions cause higher cartilage degeneration in diverse age groups. Furthermore, it was suggested that kneeling or squatting work positions (analogous to the BK 2112) produce more severe cartilage damage or other distributions thereof compared with patients in low knee-loading professions.

A total of 1199 patients with knee pain (history of 3 months or more) underwent arthroscopic operations. Cartilage lesions were classified according to the ICRS (International Cartilage Repair Society) protocol. The grading of joint degeneration was quantified by using the WOAKS (whole organ arthroscopic knee score). Patients were divided into 5 age groups (24-39-51-64-75 years) by analysis of cluster centres.

In 80.6% (n = 1086) the preoperative radiography suggested signs of a knee osteoarthritis. There was a range from grade I to grade III osteoarthritis according to the Kellgren-Lawrence score. Older female patients had knee osteoarthritis significantly (p = 0.027) more frequently. The grade of osteoarthritis correlated significantly with the patients' age (p > 0.001). The mean WOAKS was 16.6 +/- 13.7 points. There was a continuous increase of WOAKS from 8.2 +/- 5.1 in 24-year-old patients to 24.2 +/- 16.3 points in 75-year-old patients (p < 0.001). In about half of the cases cartilage lesions within the patella and trochlea were evaluated. Most frequently we recorded cartilage lesions within the mean bearing zone of the medial femoral condyle (96.2%) and the medial tibia (57.7)%. Only about a third of our patients suffered from cartilage lesions within the mean bearing zone of the lateral condyle and tibia. The frequency of cartilage lesions and the severity of the lesions grade was significantly less within the non-loaded margin of the surfaces. In 45 knees (3.8%) we found intraarticular osteophytes located: medial (n = 9) and lateral (n = 3) patella margin, intracondylar notch (n = 12), medial tibia (n = 9) and lateral margin of the lateral tibia (n = 4), lateral femoral condyle at the intersection to the lateral trochlea margin (n = 3). The occurrence of osteophytes correlated with the patients' age and the radiological grade of the osteoarthritis. There were no differences with respect to the profession within the age groups. In the non-adjusted WOAKS, patients with hard knee-loading work had a WOAKS of 16.8 +/- 13.9 points and patients with soft work a score of 17.2 +/- 14.3 points (p = 0.583). Differences in the frequency of cartilage distributions within the judged regions of the knee with respect to professional burden were also not evaluated. The same held for the frequency of intraarticular osteophytes.

Despite there is a known relation between occupational load and knee osteoarthritis no relation to cartilage degeneration was found in our arthroscopic investigation. For better understanding of work-related knee osteoarthritis prospective studies are needed urgently.