Hi, thanks for writing to HCM.
All the symptoms given in your description are manifestations of Lyme's disease. This disease typically afffects skin, joints and nervous system.
Typically, the knee joints are involved mostly in Lyme's disease though other joints may also involve.
An xray of your knee joint will diagnose if the swelling is arising from the bone.
An open biopsy
of the swelling is mandatory to know its histopathological diagnosis.
Hope this information is helpful . Good day