The objective of the proposed work is to determine whether administration for 12 months of romosozumab followed by 12 months of denosumab will maintain bone mass at the knee in subjects with subacute SCI compared to 24 months of denosumab administration alone.

Sublesional bone loss after acute spinal cord injury (SCI) is sudden, progressive, and dramatic. After depletion of bone mass and the loss of architectural integrity, it may be difficult, if even possible, to restore skeletal mass and strength. Romosozumab is a human monoclonal anti-sclerostin antibody bone anabolic agent that recently gained FDA approval to treat osteoporosis in postmenopausal women. This study will test the ability of romosozumab administered in FDA-approved therapeutic doses for 12 months to prevent loss of BMD to regions of interest of the lower extremities in persons with subacute SCI; attention will be focused to the knee region (distal femur), but the proximal tibia and hip regions will also be acquired and analyzed. The ability of denosumab to preserve the gains in BMD attained with romosozumab will be determined.The romosozumab + denosumab group will be compared to a group that receives 24 months of denosumab.

In persons with acute/subacute motor-compete SCI (<6 months since SCI), the primary objectives in the intervention group are to maintain baseline values of sublesional distal femur aBMD at 12 months after single drug therapy (12 months of romosozumab) and at 24 months after sequential dual drug therapy (12 months of romosozumab followed by 12 months of denosumab). This dual drug intervention group will be compared to a group that receives denosumab for 24 months; each active drug group will be compared to a historical control (placebo) group.

Inclusion Criteria:

1. Traumatic motor-complete or incomplete SCI C4-L2 (AIS grade A-C);
2. Duration of SCI less than 6 months;
3. Males and females (premenopausal) between the ages of 18 and 55 years old; and a safe range of BMD right above the knee as determined by study staff review;

Exclusion Criteria:

1. Active and/or history of coronary heart disease or stroke;
2. Bone cancer;
3. Long-bone fracture of the leg within the past year;
4. History of prior bone disease (for example, Paget's hyperparathyroidism, osteoporosis, etc.);
5. Postmenopausal women;
6. Men with known low functioning tests before SCI;
7. Drugs geared toward increasing BMD longer than a six month duration after SCI;
8. As determined by study staff review of my medication history of glucocorticoid administration longer than three months duration within the last year
9. Abnormalities of my endocrine glands such as hyperthyroidism, Cushing's disease or syndrome, etc.;
10. Severe underlying chronic disease (for example chronic obstructive pulmonary disease (COPD), end-stage heart disease, chronic renal failure);
11. Heterotopic ossification (HO) of the distal femur (the knee end of the thigh bone). HO is a condition where bone tissue forms outside of the skeleton. If HO is found in any other area than the distal femur it will not prevent my participation in the study.;
12. History of chronic alcohol abuse;
13. Diagnosis of hypercalcemia (high levels of calcium in the blood);
14. Pregnancy;
15. As determined by study staff review of my medications a bisphosphonate for heterotopic ossification (HO), or other medications to treat osteoporosis other than calcium and vitamin D;
16. Current diagnosis of cancer or history of cancer;
17. As determined by study staff review of my medications, prescribed moderate or high dose corticosteroids (>40 mg/d prednisone or an equivalent dose of other corticosteroid medication) for longer than one week, not including drug administered to preserve neurological function at the time of acute SCI; and
18. Life expectancy less than 5 years.