'DWTS' Celeb Janel Parrish -- Rehearsal Injury Makes Final Performance Iffy (VIDEO)

Janel Parrish just had her chances of winning the Mirrorball Trophy derailed ... at least that's the way it looks after she suffered a gnarly injury during rehearsal.

TMZ just got this video of the "Pretty Little Liars" star and Val Chmerkovskiy practicing lifts. Something bad clearly happened because you see her dissolve into tears as she hobbles to a room where doctors examine her.

It looks like she suffered a broken or compressed rib.

She hasn't been counted out, but it doesn't look good. The finals are tonight.