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Osteoarthritis or an associated tendinitis certainly can cause bony growth that may be felt as a bony lump. This is a similar process that can be seen on x-rays as bone spurs. The exact location would determine whether it would be from arthritis vs tendinitis.
There are other causes of bony lumps, including healing from prior trauma or other damage to the bone. Rarely, there are also growths of the bone that are possible. But bony growth secondary to an underlying arthritis or tendinitis is the most likely cause of a bony lump near the knee.
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Yes. I noted above that growths of the bone can rarely occur. Some of those growths are benign and some are cancer. Of people that present with a bony lump, it is a very small percentage in whom it is found to be cancer, but yes, it is possible.
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