Need Advice: Could My Dog’s Injury Be Spinal or Hip-Related Instead of an ACL Tear?

A few weeks ago, she ran full speed into a tree, hitting her left back leg/hip area. She wasn’t phased and kept playing, but later that night, she showed subtle discomfort with excessive stretching. I took her to the vet twice—once for an assessment and again for a follow-up. Both times, they saw no clear signs of injury and suspected a soft tissue issue.

Since then, I eased up on restrictions and noticed a slight bunny hop gait. Last night, while playing with a big dog in soft sand, she did a barrel roll mid-run, almost like she was avoiding putting full weight on her left back leg. Afterward, she trotted with an abnormal gait—not limping, but seemed down and hesitant to get out of my truck. No yelping or whining, just more reserved.

Today, she widens her eyes more intensely when I gently pet around her left hip/leg/lumbar area. She walks mostly normal but slightly sticks that left leg outward and doesn’t seem to lift it as much. Despite that, she’s mobile, wants to go for walks, has an appetite, and hasn’t whined. Since yesterday’s incident, she has been lifting her leg while peeing, which she wasn’t doing before. She’s on trazodone/carprofen and has been a bit out of it.

Does this sound like a soft tissue setback, or should I be more concerned about a deeper spinal/hip issue?