Damage w/o trauma?

I have been diagnosed with MCL damage based on physical manipulation and an MRI, but have never suffered any trauma to the knee. MRI showed quite a bit of fluid present. Pain and swelling started in the last 6 months or so, sometimes in both knees. Pain at the MCL attachment point is present in both knees. I have a history of gout, which is currently under control. Lyme disease test was "borderline", and I have been prescribed doxycycline, 200mg/day, 10 days. I have no history of gonococcal, streptococcal, or staphylococcal infection, but have been exposed (asymptomatically, AFAIK) to Coccidioides immitis (valley fever) fungus.

Is ligament damage always a result of trauma, or are there other possible causes?

Thanks.