KneeInstability after PCL avulsion Polio

I am a 45-year-old male with PPRP@RLL with equinus deformity, ~6 cm limb length discrepancy & knee hyperextension while walking. After deformity correction, I was able to walk without hand-to-thigh gait and was fine till 2021 Dec. Later I developed progressive arthritis of the foot/ankle, knee, and hip. 3 months ago I had a fall. Initial CT/MRI showed an undisplaced PCL avulsion fracture. A repeat CT showed a comminuted minimally displaced PCL avulsion fracture (largest  ~0.9 × 1.1 × 0.7 cm with ~2.5 mm displacement). After ~2 months, a third CT reported a partially united PCL avulsion fracture with no displaced fragment. I was with a knee brace for 3 weeks and was advised full weight bearing with a walker one week ago. However, when I load the leg, I feel marked knee instability (shaky / giving-way sensation) and poor control, even with the walker, little pain knee backside. I am seeking guidance on expected functional recovery and reasons for persistent instability in my knee.