Phenotypic Variation in Complex Regional Pain Syndrome: Comparison Between Presentation in Knee Alone or in Ankle/Foot.

OBJECTIVE

To compare the phenotypes of patients with complex regional pain syndrome (CRPS) of the knee to those with CRPS of the ankle/foot.

SETTING

A retrospective study.

SUBJECTS

Patients with CRPS of the knee and patients with CRPS of the ankle/foot.

METHODS

We used electronic patient databases to identify patients with CRPS of the knee and patients with CRPS of the ankle/foot. The following variables were recorded: age, gender, duration of complaints, initial injury, and symptoms and signs. Frequency distributions and statistical significant differences between the groups were determined.

RESULTS

Included were 50 patients with CRPS of the knee and 64 patients with CRPS of the ankle/foot. These patients were all diagnosed with CRPS according to the criteria used at the time of diagnosis. No significant differences were found in demographic characteristics. A few symptoms and signs appeared to be proportionally more prevalent in patients with CRPS of the ankle/foot. However, patients with CRPS of the knee suffered significantly longer from the disease than patients with CRPS of the ankle/foot.

CONCLUSIONS

Some signs and symptoms appeared to be statistically significantly more prevalent in CRPS of the ankle/foot than in CRPS confined to the knee. We conclude that the phenotypes of CRPS confined to the knee and CRPS of the ankle/foot are comparable, but not identical. This can be a reason why CRPS in patients with pain of the knee, that is disproportionate to the initial trauma, is sometimes not recognized.