4 Essential Facts About Knee CRPS: Understanding Complex Regional Pain Syndrom

Are you looking for comprehensive and reliable information on the causes and recovery time of Complex Regional Pain Syndrome (CRPS; orSympathetic Reflex Dystrophy, RSD), specifically localized to the knee?

This blog post aims to address the main questions that internet users have regarding the healing time of knee CRPS, whether it occurs after a knee replacement, surgery, or without an identified cause.

As a physiotherapist with over 11 years of experience, I have had the opportunity to treat people in this context. This article is based on:

👩🏽‍⚕️ my experience as a physiotherapist;
📚 my in-depth research in international medical literature.

I hope to reassure you about the evolution of this problem, which can be lengthy at times. Take comfort in the fact that it is a known issue and is a subject of great concern for healthcare professionals and research teams.

Hundreds of studies are published each year on CRPS, and our understanding of it continues to improve.

All references to the studies I mention are listed at the end of the blog post. I am also available to answer any questions you may have in the comments section.

What does CRPS really mean?

Before we talk specifically about the causes of CRPS let’s make sure we’re talking about the same thing 🙂.

The different terms

As is often the case in medicine, different terms are used to refer to the same thing. This article addresses Complex Regional Pain Syndrome (CRPS), also known as:

• Reflex Sympathetic Dystrophy (RSD)
• Chronic Pain Syndrome
• Nerve Disorder Pain
• Chronic Regional Pain Syndrome
• Causalgia
• Sudeck’s Atrophy
• Shoulder-Hand Syndrome
• Amplified Musculoskeletal Pain Syndrome
• Neurovascular Dystrophy

This blog post is relevant to you, regardless of the way your CRPS has been referred to! In fact, I will often use this designation “CRPS” throughout the rest of the blog post. It’s a shorter term!

Symptoms and diagnosis of knee CRPS

The diagnosis of CRPS is made when various symptoms are observed in a joint of the body. It often occurs in an extremity (foot, hand), and quite frequently in the knee:

• Intense and continuous pain that is disproportionate to any mechanical or physiological problem that may be the underlying cause.
• Sensory or circulatory disturbances in the skin, swelling, redness, and warmth (at least initially). Sometimes loss of feeling in foot.
• Impaired motor function: difficulty moving the affected body part as before.
• Stiffness: the joint is no longer as mobile as before.

Once the medical team has ruled out any other possible causes for these symptoms, the diagnosis of complex regional pain syndrom is made.

CRPS most commonly occurs around the age of 40, especially in women.

MRI, Scintigraphy, X-rays: No longer necessary

Nowadays, imaging tests (MRI, X-rays, bone scintigraphy) are no longer necessary to diagnose CRPS (RevMed 2019). History-taking and clinical examination are sufficient.

When imaging tests are still performed, they often reveal bone demineralization. However, identifying this does not provide more specific treatment options. That is why imaging can be omitted.

The diagnosis of knee CRPS is made when severe pain is observed in the knee, accompanied by other symptoms (sensory, circulatory, or motor disturbances) and not explained by any other cause.

What are the causes of knee Complex Regional Pain Syndrome?

Let’s first discuss the general causes of CRPS, followed by the more specific causes of knee CRPS.

We will then delve into what happens in our bodies when we have CRPS. In medicine, we use the term “physiopathology” to describe the disruptions in normal body function. Finally, we will explore whether purely psychological factors can be responsible for it.

General causes

CRPS generally occurs after:

• Trauma to the musculoskeletal system (fracture, surgery, sprain, etc.)
• Stroke (cerebrovascular accident)

This is particularly the case when extremely severe pain (rated above 5/10 by patients) is observed one week after the trauma, or when the traumatized limb has been underutilized or excessively immobilized.

Sometimes, CRPS can occur without any identifiable triggering factor.

CRPS is more often attributed to trauma to a limb or a stroke. Occasionally, it is impossible to identify a specific cause.

Specific causes to the knee

Knee CRPS most commonly occurs after knee surgery, specifically:

• Total knee replacement (or unicompartmental knee replacement). This is a rare complication. A study involving 110 individuals who underwent knee replacement described that 13% of them had CRPS six months later (Bruehl 2022). Some studies even suggest a higher frequency. However, a research team argues in favor of overestimation (Kosy 2018). I find their argumentation solid and relevant. It reflects the numbers I have observed in my practice: I have only seen three cases of algodystrophy out of hundreds of knee replacement patients.
• After knee arthroscopy.

CRPS can also occur after other knee traumas (sprains, falls without fractures or sprains). Sometimes, no triggering event can be identified, but it does not challenge the diagnosis of CRPS.

Knee CRPS most commonly occurs following total knee replacement. Less commonly, it may occur after unicompartmental knee replacement, arthroscopy, or another knee trauma. In even rarer cases, no identifiable cause is found.

Physiopathology: Dysregulation of the Body Leading to Algoneurodystrophy

What reactions occur in the body after a physical trauma (or an unknown cause) that can explain the symptoms of CRPS? There are processes happening at two levels:

1. Peripheral level: In the affected area initially.
2. Central nervous system level (brain and spinal cord) subsequently.

Animal studies show that there is inflammation in the painful area, more significant than what the injury would normally cause. Inflammation is present in both superficial tissues (skin) and deep tissues (muscle, bone). The peripheral nervous system in that area also functions differently, secreting substances more extensively than usual.

The central nervous system receives information from this area, indicating that things are functioning differently than usual. Certain networks of neurons become more activated and, in turn, send information to the injured area, leading to symptoms such as pain.

When a person has CRPS, there is inflammation in the painful area, and the information about dysfunction in that area travels up to the central nervous system.

Can CRPS be caused by emotional trauma? Can CRPS be psychological?

Hundreds of people wonder each month if their CRPS (or that of their patients) may have a emotional or psychological origin. What exactly do we mean by emotional/psychological?

If we imply that the problem is solely in the mind, then we are mistaken. As we have seen, there is indeed a physiological problem, localized and not purely cerebral.

If we imply that the problem is due to a emotional trauma, or even a trauma experienced in childhood, we actually have no means to verify this information. Even if the person has experienced a “emotional trauma,” it is very difficult, if not impossible, to retrospectively link it to the onset of algodystrophy.

However, it is likely that certain psychological factors can increase the risk of developing CRPS. For example, anxiety and catastrophizing (exaggerating an event or health issue) are suspected to increase the risk of developing algodystrophy (RevMed 2019). Nevertheless, this is not found in all patients.

More specifically,

• Fear of pain during movement,
• Negative perception of the illness, and
• Poor understanding of Complex Regional Pain Syndrome

are generally associated with more pain and disability when dealing with CRPS (Johnson 2022). Could this be a potential avenue for treatment, such as trying to reassure people? Yes and no, because, as research teams explain, these variables could be biologically intrinsic to the individuals involved. Therefore, they do not provide an obvious path for improvement.

It is impossible to establish a causal link between a “emotional trauma” and CRPS. However, certain psychological factors such as anxiety may partly explain the onset of CRPS.

What is the usual recovery time of CRPS in the knee?

In this section, I will present to you the average durations of progression for CRPS, particularly for knee CRPS. It is important to keep in mind that these are average recovery time. It does not mean that you will take the same amount of time to recover. You may be one of the “lucky ones” who recover much faster. Keep hope alive!

Here is what the Prescrire review says on this subject:

The progression of CRPS varies widely, ranging from spontaneous regression in a few weeks to pain persisting for several years.

Prescrire, 2009

It is possible that your painful and bothersome symptoms may disappear within a few weeks! For some people, it can take much longer.

However, there may still be improvements or fluctuations over time. You may be able to resume your favorite activities despite having CRPS. A lengthy progression can be frustrating, and we would prefer it to be otherwise, of course. Nevertheless, it is not a sign of something more serious.

⚠️ Also keep in mind that the numbers from studies are likely more alarming than the reality. In fact, only the most severely affected individuals are closely monitored by the medical community. They are more likely to be included in studies. This can “inflate” the average progression time of CRPS.

Let’s now take a closer look at the specific figures regarding the prognosis of CRPS.

How long does it take to recover after CRPS?

A recent publication analyzed data from 22 studies involving individuals with CRPS (Johnson 2022). It reveals the following findings:

• 51 to 89% of people still experience pain and motor impairment one year after the onset of symptoms. (This means there is potentially a 1 in 2 chance of no longer experiencing any pain within a year.)
• On average, the range of motion in the affected joint is reduced by 25% one year after the onset of symptoms.
• 30 to 40% of people are still on work leave one year after, and 27 to 35% have returned to work with adaptations.

Recovey time of CRPS: 1 in 2 people no longer experience any pain or impairment within a year after the onset of CRPS symptoms.

How long does it take to recover after knee CRPS?

Only one study specifically focuses on the progression of knee CRPS. It followed 32 individuals who had this problem, on average, 11 years after the onset of symptoms. Here are some of their results:

• 16% reported being completely cured.
• Even though some people claimed to be cured, objective clinical examination did not confirm the cure.
• All people had undergone numerous treatments.
• 82% had to adapt their work or stop working.

⚠️ These are the results of a single study with a very small number of participants (32! Fewer than what a physiotherapist, for example, might see in a few years of practice, specifically for individuals with knee algodystrophy). Therefore, they should be interpreted with caution.

Based on my own experience, I am more optimistic about the progression of knee CRPS. While it is true that I may not have updates 5 or 10 years after the initial symptoms, and my memory may not be perfect (I did not keep written, objective, and usable records of assessments and progress for these individuals), here is how I would describe it:

• The majority of individuals experience a decrease in pain or stiffness within a few months.
• Even for those who do not see improvements in range of motion, resuming daily activities, sports, or work is usually possible with some adaptations (though not always necessary).

💫 We have less precise and reliable data on the recovery time of knee CRPS. There is no reason to believe that knee CRPS has a worse recovery rate than CRPS in general. Therefore, the recovery time for knee CRPS is likely to be less than a year for 1 in 2 people.

Can I work with knee CRPS?

The type of illness or injury does not determine whether one can take sick leave or be on disability. Therefore, it is possible to take sick leave for CRPS, for as long as it is necessary.

What determines the duration of your work absence is:

• The painful and functional consequences of your algodystrophy in your daily activities.
• The same consequences on your professional activities.
• The possibility of adapting your work environment to make it more compatible with your issues.
• The consideration of these consequences by the medical teams following your case.

There is no maximum or average time of work absence due to CRPS.

What can be done to recover the knee as quickly as possible?

We are now entering perhaps the most delicate part to discuss: the treatments for CRPS. I understand that if you’re taking the time to gather information about CRPS, you are eagerly seeking a solution for this condition. Whether you’re personally affected or it concerns a loved one, or even if you’re a healthcare professional (as my readership also includes healthcare professionals).

I fully understand your expectations. CRPS often causes significant pain or discomfort, which has consequences on all aspects of life. It disrupts our ability to do things as we did before, causes worries, affects our morale, and can impact our relationships, professional life, and future plans. And it can last a long time.

I would naturally love to be able to tell you that there is a miraculous natural treatment that is 100% effective and without side effects. Unfortunately, as of today, that is not the case, whether natural or otherwise.

Numerous treatments for CRPS have been proposed and tested in small studies. They aim to relieve symptoms and restore autonomy rather than curing CRPS, which often heals “on its own” over time, without a specific treatment where we can definitively say, “this is what worked.”

That’s already a good thing: for those who are determined to try various approaches, there are plenty of options to explore. However, none stand out significantly.

Here is a list of these different treatments, some of which are practiced by physiotherapists. Treatments marked with a ✅ have some evidence of effectiveness compared to a placebo or standard care (Cochrane 2013 and 2022):

• Various medications for pain relief (bisphosphonates ✅, calcitonin ✅, daily intravenous ketamine treatment ✅, morphine, corticosteroids).
• Physiotherapy.
• Occupational therapy.
• Graded motor imagery ✅.
• Mirror therapy (after stroke) ✅.
• Transcutaneous electrical nerve stimulation (TENS is safe).
• Scottish shower.
• Continuous peripheral nerve blocks (administration of a pain medication near a nerve).
• Biofeedback.
• Relaxation techniques.

I have written a more comprehensive blog post on medical, physiotherapy, and natural treatments for knee CPRS (coming soon in English).