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.  With the lameness being in the same limb, it seems possible that the initial truama could have caused the current problem.  The fact that all of the other joints seem normal and the lameness is unilateral also lead us to believe that this problem could be due to trauma. 
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 and displacement of the infrapatellar fat pad. 
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.  These last possibilities seem less likely than a cranial cruciate ligament tear, but they will be kept as ruleouts until the results of the specialty exams are obtained.