Severely Obese? Watch Your Step!

Complete dislocation of the knee is a rather rare but generally severe traumatic injury.

While high-velocity dislocations are typically associated with traffic accidents or falling from a significant hight, low-velocity dislocations generally result from athletic endeavours.

A paper by Frederick Azar and colleagues from the University of Tennessee, Memphis, describes a series of patients, who incurred knee dislocations that occurred during activities of daily living, such as stepping off a curb, stepping off a stair, tripping over the carpet, or simply falling while walking.

In their paper, published in the American Journal of Sports Medicine, the authors describe a series of 17 patients presenting with such ‘ultra-low-velocity’ knee dislocations.

Perhaps, not surprisingly, all 17 patients were clinically obese, with 13 patients (77%) having Class 3 obesity (BMI>40). In fact, 7 patients (40%) had a BMI greater than 50.

Unfortunately, all 17 patients had ligament injuries, 7 had neurological injuries, and 7 had injuries to their popliteal artery.

However, no nerve injuries occurred in patients with a BMI less than 42, and no vascular injuries occurred in patients with a BMI less than 48. Those with nerve injuries had an average BMI of 47 (range, 42-67); those with vascular injuries, 54 (range, 47-60); and those with both nerve and vascular injuries, 60 (range, 51-68).

While surgical ligament reconstructions were done in 8 patients and popliteal artery repairs in 7, two patients require above-knee amputations and one patient died from cardiac arrest a week after the accident.

Follow up at about 2.5 years after the accident showed better outcomes in those patients, who underwent ligament reconstruction, but overall function remained rather poor.

These results indicate that

1) neurovascular injuries are frequent with these ultra-low-velocity dislocations in severely obese patients,

2) the likelihood of combined neurovascular injury tends to increase as BMI increases, and

3) surgical ligament reconstruction with emphasis on posterolateral corner repair appears to improve outcomes.

These findings are a stark reminder to educate our severely obese patients to ‘watching their step’.

Clinicians must remember that patients with severe obesity often cannot see where they put their feet and are therefore at considerable risk of missing a stair or tripping over objects in their path.

Occupational therapists may likely play a considerable role in educating patients about the importance of maintaining a clutter-free environment and be wary of other obstacles that can increase the risk of tripping or falling (such as de-cluttering the home environment, attention to flooring, etc.).

In Canada, the danger of slipping and falling on icy sidewalks should not be underestimated.

I would certainly like to hear from my readers on this issue and how they may have dealt with it in their environments.

Duchesnay, Quebec