Previous Injury

Yuletide greeting all. Ok here's the deal, did the usual started lifting, concentrated on upper body, neglected the leg's, glutes. Decided to bring them up to speed with the rest of my bod.
Here's the catch........At age 21 i was stabbed in the leg, the blade went all the way through two inches from my balls, into the inner thigh. It severed the major artery and sliced through several nerve fibers. After a investigative op to attemp to repair the damage, i was left with a 42 stich scar running in a "S" shape down the front of my thigh, and a small amount of Muscle tissue was removed due to excess dammage.
Anyway after trying to complete hack squats i find that i'm cramping up in the said quad, no matter how light i go. Also tried to do standard squats but almost killed myself in the process.
Does anyone have any sugestions short of amputation, that'll help me cross this hurdle?

Have a great Christmas all
DJ