Hypothesis #1

7 months ago Titan fell off of the bed and the fall resulted in a weight bearing hindlimb lameness.  This lameness resolved within a month, but it recurred again six months later.  A variety of conditions could result in these clinical signs.  
Our primary hypothesis that seems to best fit the clinical signs is a partial tear of the cranial cruciate ligament.  The initial tear from the fall off of the bed could have healed and a subsequent tear would lead to the recurring lameness.  In most cases a partial tear will progress to a complete tear in time.  Radiographic findings for this traumatic lesion would reveal joint effusion, displacement of the infrapatellar fat pad.  The medial buttressing of the stifle joint is almost pathopneumonic for a cranial cruciate ligament tear.  
Other traumatic injuries could also result in stifle joint pain and laxity.  A tear in the quadriceps with inappropriate healing could result in malalignment of the patella.  A femure fraction could result in malalignment upon repair.  Also, the fall from the bed could cause laxity in the ligaments surrounding the joint.  
The first two would be visible through the malpositioning of the bones in the stifle joint.  The third could be evaluated best under sedation.