I have not squatted in a long time. I’ve been recovering from very bad patella tendinitis for the past 10 months and have finally become pain free so I thought I can try the squats in my upper/lower program. Next day I felt slight discomfort and pain in my patella. Up to this point I have been doing lunges and light weight Bulgarian split squats and goblet squats. I am very leery of doing barbell squats now and am wondering if lunges, split squats or leg presses are acceptable subs for the squats in the upper/lower program? Obviously they are not ideal but I don’t want to risk getting injured again. If I swapped out the squat for one of those exercises, would I have to modify the program in anyway?