Why does my penis become hard but not stay upright (remains hanging) during erection?

Incomplete Penile Rigidity During Erection

You are experiencing erectile dysfunction characterized by inadequate axial penile rigidity—your penis becomes engorged (hard) but lacks sufficient structural stiffness to maintain an upright position, causing it to hang despite tumescence. This represents a failure to achieve full rigidity necessary for penetration, which is a distinct form of erectile dysfunction that may occur even with normal blood flow 1.

Understanding the Problem

Your symptom reflects a specific biomechanical failure in the erectile process:

• Normal erection requires both adequate blood inflow AND sufficient intracavernosal pressure to compress the penile veins and create rigidity 2
• Axial penile rigidity (the stiffness that allows the penis to stand upright and resist buckling) depends on multiple factors beyond just blood flow, including intracavernosal pressure, penile tissue mechanical properties, and penile geometry 1
• The penis contains three erectile bodies: two corpora cavernosa (responsible for rigidity) and the corpus spongiosum (which forms the glans and remains softer) 3
• Full rigidity requires pressure above 80-100 mmHg within the corpora cavernosa, combined with compression of venous outflow and contraction of pelvic floor muscles 2

Most Likely Causes

Venous Leak (Veno-occlusive Dysfunction)

• This is the most common cause of your specific symptom pattern—blood enters the penis but drains out too quickly, preventing adequate pressure buildup 4
• The tunica albuginea (outer sheath) normally compresses veins during engorgement, but if this mechanism fails, the penis fills but cannot maintain rigidity 2
• Aging and fibrosis reduce smooth muscle cells in the corpora cavernosa, impairing the compression mechanism that traps blood 2

Inadequate Pelvic Floor Muscle Function

• Pelvic floor muscles (bulbocavernosus and ischiocavernosus) normally contract to raise intracavernosal pressure above arterial inflow pressure, achieving full rigidity 5, 2
• These muscles may weaken with age or disuse, preventing the final phase of rigidity that makes the penis stand upright 2

Structural/Tissue Abnormalities

• Reduced tunical distensibility or abnormal penile geometry can prevent adequate rigidity even with normal blood flow 1
• Peyronie's disease or penile fibrosis can cause compliance problems that prevent venous compression 4

What You Need to Do

Immediate Evaluation Required

You need a comprehensive urologic assessment focusing on:

• Complete medical and sexual history including onset timing, presence of morning/nocturnal erections, medication use, cardiovascular risk factors, and psychological factors 6
• Physical examination of the genitalia to assess for penile plaques, deformities, or anatomical abnormalities 6
• Morning serum total testosterone level to rule out testosterone deficiency (total testosterone <300 ng/dL) 6
• Penile Doppler ultrasound or duplex ultrasonography to assess arterial inflow and venous outflow dynamics 4
• Dynamic cavernosometry/cavernosography if venous leak is suspected—this directly measures the ability to maintain intracavernosal pressure 4

Treatment Options (Based on Underlying Cause)

First-Line: PDE5 Inhibitors

• Phosphodiesterase-5 inhibitors (sildenafil, tadalafil, vardenafil) enhance nitric oxide-mediated smooth muscle relaxation and increase blood flow 7, 2
• These work by inhibiting PDE5, which increases cGMP levels in the corpus cavernosum, promoting smooth muscle relaxation and arterial inflow 7
• Tadalafil requires sexual stimulation to be effective and has no effect without it 7
• Success rate varies but these should be tried first unless contraindicated 4

Pelvic Floor Muscle Rehabilitation

• Pelvic floor muscle exercises have been shown to improve erectile function to a degree similar to PDE5 inhibitors in men with ED 2
• These exercises strengthen the bulbocavernosus and ischiocavernosus muscles, which are critical for achieving full rigidity 2
• This approach is complementary to PDE5 inhibitors, not competitive, as they address different mechanisms 2

Intracavernosal Injection Therapy

• If oral medications fail, intracavernosal pharmacotherapy (alprostadil, papaverine, phentolamine combinations) directly induces erection by bypassing oral absorption 4
• This is particularly effective for venous leak when combined with a constriction device 4

Vacuum Constriction Device

• Vacuum devices create negative pressure to draw blood into the penis, with a constriction ring placed at the base to trap blood 4
• This mechanically compensates for venous leak and can be effective when medications fail 4

Surgical Options (Last Resort)

• Venous ligation surgery may be considered for documented venous leak, though success rates are variable 4
• Penile prosthesis implantation is the definitive treatment for refractory cases but should only be considered after all other options have failed 4

Critical Pitfalls to Avoid

• Do not assume this is purely psychological just because you can achieve some degree of hardness—the lack of rigidity suggests a physiologic problem with the veno-occlusive mechanism or pelvic floor function 1
• Do not delay evaluation—erectile dysfunction is a marker for cardiovascular disease and other health conditions that warrant assessment 6
• Do not use PDE5 inhibitors if you take nitrates for heart disease, as this combination causes dangerous hypotension 7
• Do not accept "normal" test results as conclusive—patients with normal hemodynamic studies may still have tissue mechanical or geometric abnormalities causing inadequate rigidity 1

Next Steps

Schedule an appointment with a urologist who specializes in erectile dysfunction for comprehensive evaluation including Doppler ultrasound and consideration of dynamic cavernosometry 6, 4. Begin lifestyle modifications that improve vascular health (exercise, smoking cessation, weight loss, blood pressure control) as these enhance nitric oxide production critical for erectile function 2. Consider trial of a PDE5 inhibitor if not contraindicated, as this addresses the most common reversible causes 7, 2.