Dr. Conway McLean

The world is full of medical oddities, conditions which defy our understanding. Examples abound, from chronic fatigue syndrome to Charcot joints; many “interesting” diseases can afflict the human body.

One of them certainly is Mueller-Weiss Syndrome and the associated collapsing foot deformity.

Our feet are tasked with an unenviable role, that of supporting and transporting the human form. Whether sprinting to catch the dog or standing long hours at work, the physical stresses experienced are tremendous, especially over the years.

Which is why any change in alignment of one’s bony architecture will lead to functional changes, and orthopedic issues eventually ensue.

As you may have guessed, two physicians whose names are attached to the condition wrote about this, in which the navicular bone becomes misshapen, but in a particular fashion. The navicular is the bone at the top of the arch, considered the keystone, on the inner side of the foot. In Mueller-Weiss, the navicular bone softens and then flattens. But only one part of it.

The consequence is a gradual collapse of the arch without the rolling effect seen most commonly with a progressive collapsing foot type. The altered foot alignment which develops in MWS often leads to symptoms as some vital structure involved in stance and gait becomes stressed.

It may affect tendons or ligaments, joints or muscles, but when foot alignment changes, an individual’s biomechanics will be disturbed.

The diagnosis of Mueller-Weiss is often missed because the radiographic changes can be subtle. Another factor is that many health care providers are unfamiliar with it. Thus, we cannot say for certain the frequency with which it appears.

An X-ray looking down onto the top of the foot can demonstrate some distinctive changes of the navicular, with half of the bone flattening, giving the bone the shape of a comma.

Mueller-Weiss generates more than just pain; it often produces true deformity. As half of the navicular collapses, the bone behind it, the talus, falls forward once denied of support.

This predictably leads to complex bony deformity and the resultant biomechanical changes in the feet, ankles, lower legs and other areas of the body. The arch collapses without the heel turning outward, which is normally a characteristic of all the most common collapsing foot deformities.

Many individuals with less severe forms of MWS live their lives with milder complaints, unaware of their altered navicular bone. It is more common in females and usually involves both feet. Symptoms typically develop in the fourth to sixth decades, although the bone changes clearly occur much earlier, likely when the bones of the feet haven’t fully solidified.

In the presence of obesity, there are greater compressive forces between the bones of the arch, especially on the navicular. Indeed, the statistics demonstrate an increased incidence of MWS when there is a higher body mass index — the infamous BMI. This might lead one to assume this syndrome, a process of bone death, occurs because of mechanical forces.

This concept proposes that abnormal foot architecture causes excessive compressive forces on the navicular, leading to bone death. Or maybe it’s a problem with ossification, whereby the process of converting the foot bones from cartilaginous to bony is delayed. The timing of this process is one that takes place in everyone during our childhood years. Perhaps some delay allows the fragmentation of the navicular? Theories abound, while answers are few.

No classification system exists allowing us to determine the optimal treatment. Certainly, therapies can be broken down into conservative versus surgical, but MWS tends to be treated on a case-by-case basis, according to the training and experience of the individual physician. We do not know what is optimal or what technique works best.

The chronic joint stress associated with the anatomical changes of Mueller-Weiss can result in inflammation of various soft tissue structures, treatable with the traditional methods. Anti-inflammatories, whether orally administered or injected, help with the pain, but only temporarily, as recurrent stress to some structure leads to the recurrence of inflammation.

With time, numerous joints are prone to degenerative changes, typically described simply as “arthritic.” At this point, fusion or replacement are the only options. Both entail numerous potential complications. Joint function is often compromised, stressing neighboring structures.

Sometimes these damaging changes can be prevented with some type of bracing or support. This can be a prescription arch support or something more substantial like a foot-ankle brace. Ligaments may need stretching or muscles strengthening, determined by a careful analysis of structure and function.

The most striking feature of Mueller-Weiss is probably the unusual flat-foot deformity which can accompany the disease. The symptoms, often an insidious pain from the middle of the foot, can result from innumerable conditions. But appropriate X-rays, along with a careful exam, will lead the astute practitioner to the diagnosis of Mueller-Weiss Syndrome.

Of course, the next question is what to do about it.

This article was written by Dr. Conway McLean of Superior Foot and Ankle Centers as part of his weekly Health Matters column. He is a triple board-certified physician practicing podiatric medicine in the Upper Peninsula, with offices in Marquette, L’Anse and Escanaba.