What Happens When the Nervous System Gets Stuck on High Alert?
Let's talk about penises.
Specifically, penises that feel a little weirder than usual.
Penises that maybe had a minor local physical trauma that triggered a runaway pathological loop in the nervous system.
Hard flaccid syndrome (HFS) is a poorly understood condition characterized by a penis that remains somewhat rigid, contracted, or firm even when the person is not sexually aroused. It can come with a constellation of other symptoms like penile pain, testicular pain, a change in sensation, a feeling of coldness or poor blood flow, changes in appearance of the penis, erectile difficulties, urinary symptoms, perineal discomfort, and other pelvic floor dysfunction.
The physical symptoms are only part of this experience. There's often a tremendous amount of distress, uncertainty, and frustration attached to a condition that is deeply personal and often poorly understood by healthcare providers.
We don't have a definitive answer yet about specifically why this happens, but I think there's an interesting conversation to be had about hard flaccid syndrome and what we know about complex regional pain syndrome (CRPS), which has a tremendous amount of research and is still somehow (kind of) poorly understood because it doesn’t act like a normal tissue problem.
Did you know the nervous system itself can trigger changes in blood flow, nerve function, skin temperature and color, and sensitivity to physical stimuli? The brain is plastic and this is an example of maladaptive neuroplasticity. Because the brain is plastic, we also know that it can change back and become functional again. This is good news!
First, let's talk about CRPS
CRPS is a chronic pain condition that can develop following an injury, surgery, or other trauma. It most commonly affects a single extremity, such as an arm or leg.
CRPS isn't just an injury that continues to hurt beyond a normal healing timeline. It's a condition that involves changes across multiple body systems, including sensory processing, motor function, and inflammatory processes.
People with CRPS may experience:
Pain that seems disproportionate to the original injury
Allodynia (pain from something that ordinarily shouldn't hurt)
Hyperalgesia (an amplified response to painful stimuli)
Changes in skin temperature or color
Changes with sweating or swelling
Changes in movement, muscle activation, and motor control.
Changes in the appearance or health of skin, hair, nails.
In other words, an injury can become the starting point for a much more complex and distorted localized problem.
Maybe there was an original tissue injury that has healed, but the nervous system continues behaving as though the area still needs protection.
This doesn't mean the symptoms are imaginary or made up. It means the mechanisms perpetuating the symptoms may be different from the mechanisms that started them.
What the heck does this have to do with hard flaccid syndrome?
There are some cool parallels.
Hard flaccid syndrome is often reported following a triggering event or trauma involving the penis or perineum, such as an injury during sexual activity, an erection with excessive duration, delaying a strong bladder urge for way too long, a really big bump on your mountain bike, or another form of trauma (or perceived trauma).
A proposed theory involves an initial injury or irritation of penile neurovascular structures, followed by increased sympathetic nervous system activity, decreased blood flow, and increased pelvic floor muscle activity (tighter muscles).
The sympathetic nervous system is your fight, flight, or freeze nervous system state that thinks there’s a tiger in the next room.
Parasympathetic activity (the opposite of sympathetic) aids in erection through smooth muscle relaxation and increased blood flow. This is one reason you sometimes wake up with an erection. We need sympathetic activity for orgasm. It’s a fun dance, no?
If the systems coordinating these responses become dysregulated, the result might be more complicated than a muscle spasm or normal pelvic floor guarding in response to an actual threat. This is one hypothesis of why you may be experiencing a persistent semi-rigid penile state, changes in sensation, temperature changes, pain, and difficulty achieving or maintaining an erection. It might be driven by a nervous system stuck in danger alarm.
And here's where the CRPS comparison comes back: both conditions invite us to consider whether a local triggering event can lead to a persistent regional disturbance that involves multiple body systems that are highly dependent on a regulated nervous system.
I'm not suggesting hard flaccid syndrome is CRPS of the penis. They are distinct conditions, and there is currently basically zero evidence to establish that they share the same underlying pathology (or lack of pathology?). But CRPS might be a useful framework for thinking beyond the original injury, why symptoms can be so persistent, and why your physician has no idea what to do with you.
The nervous system is not a light switch
One of the biggest problems with explaining persistent pain is the tendency to divide symptoms into two categories:
Symptoms with tissue injury.
Symptoms without tissue injury (or persistent symptoms beyond the normal healing timeline)
It’s also commonly assumed that with no tissue injury, the symptoms must be psychological. This probably doesn’t mean what you think it means. It doesn’t mean symptoms are made up or “in your head,” it’s more like a neural circuit malfunction. When there is no problem with the hardware, the problem is probably with the software.
The brain is always receiving information from the body, interpreting that information, and adjusting its output. When an area becomes painful or threatened, the nervous system may increase protective responses, which usually means the muscles are tighter or more guarded.
When this guarding happens, normal physiological input may be perceived as painful or alarming. Someone may begin monitoring the area closely because they are trying to understand what is happening. This is especially true when we’re talking about changes to a penis, a very important part of the body for a lot of people.
This creates a cycle of doom: an initial injury or painful event transiently changes sensation, we notice an unfamiliar physical change and feel concern, we increase how much we’re paying attention, sympathetic nervous system activity goes up, we have more guarding or more pain, we do less of our valued activities, we feel annoyed or frustrated or scared, we become more guarded and we pay more attention and chronically check in, we become more scared, we become more guarded with even tighter muscles, etc. (you get the point).
This isn't a conscious decision. You’re not doing this on purpose! Nobody is choosing to maintain a pelvic floor contraction because they're worried about their penis. It just happens because we’re human. Congratulations, you’re not an alien.
Can pelvic floor therapy help hard flaccid?
People with hard flaccid syndrome often present with increased pelvic floor muscle activity, tenderness, inability to fully relax, or difficulty coordinating contraction and relaxation. These people are also often experiencing a phenomenon called central sensitization, where the spinal cord and brain amplify normal or neutral sensations and you have the experience of pain, discomfort, or disconnection in response.
It doesn’t work to simply tell someone to relax their pelvic floor.
Muscle activity is influenced by a lot of different inputs and the nervous system is always in charge. A muscle that is guarding may not need stretching, aggressive manual therapy, or repeated attempts to force it to relax.
It may just need a different experience of movement and a foundation of safety.
According to the available research on hard flaccid syndrome, treatment works best when we’re working on the nervous system (the maladaptive neuroplasticity) and using mechanical strategies (like pelvic floor internal release work) simultaneously.
What might treatment look like?
Depending on the person's presentation, you might look for a medical evaluation from your PCP or urologist, pelvic floor therapy, progressive return to movement or activity with guidance to keep your nervous system feeling safe, pain and nervous system education, and addressing the emotional burden that often contributes to perpetuating these symptoms.
Understanding that your symptoms may be primarily driven by changes in nervous system processing can help reduce fear and improve self-efficacy. Living with persistent genital symptoms can affect relationships, confidence, intimacy, movement, work, school, and mental health and nobody wants that for you.
We need to reverse re-wire, like pushing the reset button on your video game. If only we had a reset button instead of having to deal with complex trauma or feelings or a nervous system that’s gone a little overboard.
A Wide Lens
What interests me most about comparing HFS with CRPS is the opportunity to move away from the idea that every persistent symptom must be explained by a tissue injury. It also offers some new insights into possible treatment modalities that may help people get better faster. Treatment that targets the nervous system and working with an informed provider can make a huge difference in how effective your treatment is.
A body part can become painful, guarded, sensitive, and functionally altered from SO MANY THINGS. Some of these don’t involve an injury to any tissue at all.
At Soft Power Pelvic Health in El Cerrito, we provide individualized pelvic floor occupational therapy for adults and older teens of all genders. If you're experiencing hard flaccid syndrome, chronic pelvic pain, urinary symptoms, sexual difficulties, or related movement concerns, pelvic floor therapy may be one part of a broader care plan.
If you're unsure whether this practice is a good fit, you're welcome to reach out with questions. We can discuss your concerns and whether an evaluation makes sense for you.
If you are ready to find lasting relief from hard flaccid syndrome, click here to schedule a pelvic floor evaluation.
A note on the evidence: HFS remains an emerging and poorly researched diagnosis. The CRPS comparison is a conceptual framework for discussing regional neurophysiological dysfunction, not a diagnostic equivalence or established treatment model. We’re doing our best!
Reference:
Goldstein I, Komisaruk BR. Hard Flaccid Syndrome Proposed to Be Secondary to Pathological Activation of a Pelvic/Pudendal-Hypogastric Reflex. 2023
Hughes K, Parnham A, Lucky M. Hard flaccid syndrome. Urol News. 2018;23:1.
Yazar, R. O., Hammad, M. A. M., Barham, D. W., Azad, B., & Yafi, F. A. (2025). Successful treatment of hard flaccid syndrome with multimodal therapy: a case report study. International journal of impotence research, 37(6), 448–450. https://doi.org/10.1038/s41443-024-00955-x
This content is for informational purposes only and is not medical advice. Please consult your qualified medical provider for an individual assessment or plan of care. Seek urgent medical care for a prolonged erection lasting four hours or more, sudden severe penile pain or swelling, significant bruising after an injury, or an inability to urinate. New genital numbness accompanied by saddle numbness, leg weakness, or loss of bladder or bowel control also warrants emergency evaluation.
