Physiology of Joint Pain

Words Matter

Misconceptions in Orthopedic Language and Their Implications

We discovered a fundamental disconnect in how medical professionals describe joint conditions. When a surgeon says a knee is "shot," they view the problem as purely mechanical—simply a matter of which surgery would be most suited to treat the issue. However, when pressed for deeper reasoning, there is little substance regarding what precisely defines a joint as being "shot."

Specifically, when the joint was narrowed or "bone on bone," the surgeon views the joint as beyond arthroscopic surgical repair and concludes that either living with the pain or total joint replacement surgery were the only options available as an orthopedic surgeon.

Over-Prescribing Surgical Procedures

This linguistic imprecision has serious consequences. The lack of clear, physiologically-based definitions leads to a binary treatment approach: if arthroscopy won't work, then replacement must be the answer. This oversimplification ignores the complex pathophysiology underlying most joint pain and eliminates consideration of alternative, less invasive interventions.

The Orthopedic Surgeon's Toolbox

Cutting, Sawing, and Implantation

It became clear through our research that there are essentially two tools in the 'orthopedic toolbox': arthroscopy and total joint replacement. Each has its specific application based on the surgeon's assessment of the joint's condition.

However, if the surgeon felt that there was little or no joint space on imaging, then there was nothing to get stuck to cause the mechanical pain and, therefore, no role for arthroscopy. The surgeon then concludes that the cause of the joint pain must be secondary to arthritis and wear and tear of the hard articular cartilage that coats the ends of the bones.

Understanding Joint Cartilage and Pain Signaling

The Two Types of Cartilage

To understand joint pain, we must first understand the anatomy. There are two distinct types of cartilage in your joints, each serving different functions:

Where Pain Actually Originates

This hyaline cartilage or Type 2 collagen serves a dual purpose: to provide a slick hard surface for the joint to slide over and to protect the underlying living bone from the mechanical trauma of the joint performing its function. You can see this hard hyaline cartilage at the end of a chicken bone—it's that smooth, shiny white surface.

Chondromalacia: The Real Culprit

Chondromalacia is the medical term for wearing out of this protective cartilage in small divots or cavities. The process is exactly like a dental cavity, and the resulting nerve pain follows the same mechanism.

When this protective enamel wears away in spots, the exposed sensory nerve endings underneath the compromised enamel now sense the pressure and trauma of daily activity. These irritated nerves communicate to the brain the sensation of pain—not because something is mechanically stuck or broken, but because the protective barrier has been breached.

Clarifying the Real Cause of Joint Pain

Cavities and Unprotected Nerves

Simply stated, if there is not a mechanical issue like a flip-flopping torn piece of the meniscus or a loose fragment of bone floating inside of the joint, there is only one other thing that can be causing the knee pain: chondromalacia, or cavities in the protective enamel, resulting in nerve irritation and pain.

From a strict orthopedic perspective, there are two treatment options: arthroscopy and total joint replacement. The decision tree is straightforward but problematic:

If the X-Ray appears to be "bone on bone" and the patient's clinical exam does not exhibit a mechanical cause of the pain, the surgeon concludes that the cause must be chondromalacia. Since these 'potholes' are the source of the pain, there is no role for an arthroscope, as it is a cutting and grinding instrument that cannot repair enamel cavities.

Prior Treatments Before AROmotion

Limited Options in Traditional Orthopedic Surgery

There is no role for the cutting and shaving of an arthroscopy since the underlying problem is chondromalacia or cavities of the articular cartilage enamel protecting the underlying bone. The only orthopedic surgical option for this problem is total joint replacement.

This binary approach left patients in an impossible position: accept chronic pain and medication dependence, or undergo major surgery with significant risks and recovery time—even when their joints were mechanically functional.

90% of Total Joint Replacement Patients Have Mechanically Functional Joints

Cut Out the Pain, Not the Joint

This statistic reveals the fundamental problem with current orthopedic practice. If the joint is collapsed, disfigured, or subluxated to a degree that the "hinge" of the joint is not mechanically capable of functioning, then total joint replacement is indeed the best solution.

However, today, over 90% of people who undergo total joint replacement have mechanically functional joints and are typically walking without the assistance of a cane or walker. These patients are not getting joint replacements because their joints don't work—they're getting replacements because their joints hurt.

This realization opened the door to an entirely different approach—one that addresses the actual source of pain (exposed nerves due to cartilage damage) without destroying a mechanically functional joint. This is the foundation upon which AROmotion was built.