I have been in physiotherapy for four months for a back injury (L3). I had a fall and jammed that area, but I'm frustrated because my psoas muscle is constantly being aggravated every time I bring my knee to my chest. The physio said he could do nothing more for me. With squats and lunges, my lower abdominals are somewhat painful as I'm constantly being pinched when performing these exercises. Can you help me get back to my old self?
Without having the specifics of your rehab or your physical therapist's assessment, one possibility is that your attempts at returning to full participation in "normal" strength training exercises may be premature. If your physiotherapy consisted predominantly of passive modalities (heat/ice, ultrasound, electric stimulation, etc.) and passive activity (assisted stretching, joint mobilization or manipulation), then you may need to take a few steps backward in your training.
Pain and trauma create some unique consequences to your neuromuscular system that will remain after the pain is gone if they are not addressed thoroughly. Your psoas may in fact be reacting in a protective mechanism (remember, the psoas attaches to the lumber spine). Unfortunately, it may be overreacting, which produces its own negative consequences such as more pain. This overreacting is what is termed a "low irritability threshold." During certain movements or exercises, the psoas is either activated when it shouldn't be or it becomes hypertonic when facilitated.
The lunge and squat can certainly produce this response. And the lower abdominals may be inhibited by the overactive psoas, thus decreasing their ability to neutralize the psoas' pull on the lumber spine.
Consider placing the psoas in a position where it can be progressively relaxed with the assistance of gravity. The rationale behind this is to eliminate any opportunity for a reflexive tightening of those hip flexor muscles.
The exercise should be done with both legs. Start with the less sensitive leg straight first. The other leg is supported on a chair or bench with the knee and hip flexed. The extended leg is in line with the hip joint and placed with the foot on a support approximately 20 inches high. The outer portion of the foot is propped so that the toes point straight to the ceiling. A step ladder can be used for this. When the leg is first placed at this height, you may get the sensation that the lower back is slightly arched. Relax in this position for up to five minutes or until the lower back feels relaxed. From here, lower your foot to the next increment – ideally five to eight inches below the first. Repeat the process until your foot is flat on the floor keeping the outside of the foot propped straight the entire time.
Hip Flexor Relax 1
Hip Flexor Relax 2
After completing this on both legs, your psoas will ideally have a higher irritability threshold. In other words, lunges may still set it off, but subtler pelvic control exercise should not. This may be a good time to practice some core control floor work. This should be done for up to two weeks, each time preceding the floor work exercises with the progressive relaxation of the psoas. I would consider avoiding the irritation provoking exercises until you feel you have mastered pelvic control in less complex exercises and without an added load.