I had an l5-s1 fusion rev/hardware removal 1 year ago. Therapy done. Why do I still have aching pain in my lt/side hip/iliac crest (tender to touch)?

Possibilities: While i rarely take iliac crest bone graft because it usually isn't necessary, when i do, my patients never complain of pain from the graft site. It definitely could be si joint pain, you should have your si joint evaluated with the 5 provocative tests for si instability. If at least 3 are positive, then an si joint injection, radioablation, or minimally invasive fusion may alleviate your pain.
Iliac pain. Pain at the iliac crest after fusion is not uncommon. A couple problems may exist. 1) bone graft donor site pain—if your doc used your pelvis bone for fusion, this is probable. 2) si pain—not uncommon after a fusion to l5-s1, can also be damaged during bone graft harvest. 3) muscular—this is the attachment point of your hip muscles/paraspinal muscles. Easily irritated if weakness occurs.
Tenderness. In my practice tenderness is a sign of muscular inflammation or irritation or sensitivity this psin is mot surgicall y treatable somrthing as simple as actrigger point injection can illuminate a mew treatment pathway and cofirm the pain generator structural pain generators are not palpable.