Introduction. Several studies have dealt with the issue of professional risk factors and onset of knee osteoarthritis (OA). In particular, occupational epidemiological studies have provided evidence that activities resulting in biomechanical overload may be linked with an increased risk of knee OA – also among farmers. To our knowledge, no cases of knee OA among chestnut farmers have been reported in the literature. Case report. We report the case of a 70-year-old Caucasian male who has worked for more than 50 years on a chestnut farm. In 2007, an X-ray and a MRI, performed after a workplace accident to his left knee, showed the presence of knee OA. His job required a range of repetitive tasks, such as squatting, kneeling, climbing, walking on sloping terrain, assuming uncomfortable postures, and lifting and carrying heavy loads for the great majority of the working day. All the aforementioned tasks are known occupational risk factors for knee OA. Regarding individual risk factors, at the time of the first diagnosis of knee OA, the worker was 64-years-old with a body mass index of 26.5 kg/m2. He reported no cases of arthritis among his relatives and no sports playing on his part. In addition, his medical history revealed the presence of two minor lumbar disc herniations and tendinitis of the long head of the biceps. Conclusion. Considering the lack of major individual risk factors for knee OA, it is reasonable to suppose that five decades of exposure to biomechanical overload as a chestnut farmer was a relevant risk factor for the onset of the disease.