HISTORY: A freshman collegiate football player presented to the athletic training facility after his first official practice, complaining of worsening, severe pain in his R greater than L lumbar region without radiation or radicular symptoms. He denied any injury during practice. He had previously reported mild low back tightness during summer conditioning workouts that resolved with rest. He and the sports health staff were aware that he has sickle cell trait. PHYSICAL EXAMINATION: Pt in severe distress with diaphoresis, agitation and restlessness Limited lumbar ROM. Tenderness in lumbar paraspinal muscles R greater than L. Non-tender abdomen, symmetric pulses x4 extremities, no neurologic deficits or costa-vertebral tenderness. HR and BP elevated. Afebrile. High-flow oxygen by mask initiated and athlete transported to ED. DIFFERENTIAL DIAGNOSIS: Lumbar muscle/myofascial strain Lumbar disc rupture Lumbar paraspinal myonecrosis Ureteral calculus Renal angiomyolipoma TESTS AND RESULTS: CMP Cr 1.7, Ca 10.6, Glu 140; otherwise normal WBC 11.8, Hgb 15.5, Hct 47.5, Plt 178 CK 747 U/L Urinalysis SpGr 1.010, Pro 30, Small blood, 2 RBC, 4 WBC, myoglobin negative MRI lumbar spine: T2 hyperintense signal in the paraspinous muscles bilaterally, R greater than L. Spine and nervous structures normal. Impression: Multifocal paraspinous muscular edema. Considerations would include strain, acute myonecrosis (given clinical history), or acute blood products FINAL DIAGNOSIS: Acute lumbar paraspinal myonecrosis in athlete with SCT TREATMENT AND OUTCOMES: 1. High-flow oxygen continued 2. IV fluids initiated and 3L NS bolus given by pressure infusion 3. IV hydromorphone prn for pain control 4. Rapid improvement in pain post IV fluid bolus 5. Inpatient admission, transitioned from IV hydromorphone to PO oxycodone 6. Peak CK of 10,169 approximately 13 hours post event 7. Discharged home hospital day 2 with CK down trending at 7,060 ,Cr 0.98, off all pain meds 8. Cleared for activity at 7 days post event 9. Completed return to play activities, returned to full practice at 11 days post event 10. No related medical issues, no visible loss of muscle bulk/tone and continued full team participation as of abstract submission