Algodystrophy: a common unrecognized cause of chronic knee pain

Hot and cold knees: exploring differences in patella skin temperature in patients with patellofemoral pain

OBJECTIVES

To investigate the distribution of patella skin temperature (Tsk) measurements and to explore the presence of temperature subgroups in patellofemoral pain (PFP) patients.

DESIGN

Cross-sectional observational study design.

PARTICIPANTS

One dataset of 58 healthy participants and 232 PFP patients from three different datasets.

MAIN OUTCOME MEASURES

Patella skin temperature, measured by physiotherapists using a low cost hand held digital thermometer. The distribution of patella skin temperature was assessed and compared across datasets. To objectively determine the clinically meaningful number of subgroups, we used the average silhouette method. Finite mixture models were then used to examine the presence of PFP temperature subgroups. Receiver operating characteristic curves were used to estimate optimal patella Tsk thresholds for allocation of participants into the identified subgroups.

RESULTS

In contrast to healthy participants, the patella skin temperature had an obvious bimodal distribution with wide dispersion present across all three PFP datasets. The fitted finite mixture model suggested three temperature subgroups (cold, normal and hot) that had been recommended by the average silhouette method with discrimination cut-off thresholds for subgroup membership based on receiver operating curve analysis of Cold=<30.0°C; Normal 30.0-35.2°C; Hot ≥35.2°C.

CONCLUSION

A low cost hand held digital thermometer appears to be a useful clinical tool to identify three PFP temperature subgroups. Further research is recommended to deepen understanding of these clinical findings and to explore the implications to different treatments.

Sympathetically mediated anterior knee pain. Scintigraphy and anesthetic blockade in 19 patients

Nineteen patients with anterior knee pain without the classical features of reflex sympathetic dystrophy (RSD) were investigated by local anesthetic sympathetic blockade. Scintigraphy was performed before the sympathetic blockade in all the cases, and the scintigraphic appearances were correlated with the clinical response. Eleven patients responded to the blockade (9 good and 2 fair). Only 1 out of 10 patients with increased scintigraphic uptake failed to respond, whereas 7 out of 9 patients with normal uptake failed to respond. Our study suggests that a sympathetically mediated component may exist in patients with anterior knee pain without RSD, and that scintigraphy is useful in identifying those patients for whom sympathetic blockade may be helpful.

Diagnosis and management of algodystrophy

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Scintigraphy in the assessment of anterior knee pain

Sixty knees presenting with chronic anterior pain were investigated. A diffusely increased uptake indicated sympathetically mediated pain provided other diagnoses such as synovitis or widespread arthrosis were excluded. Focal uptake was not specific to any one condition, but could occur in chondromalacia patellae or recent dislocations. However, the commonest appearance found in chondromalacia patellae was a normal scan. A characteristic scintigraphic appearance in symptomatic postpatellectomy knees, which has not been previously reported, was increased uptake in the femoral groove. In all the cases where no clinical or arthroscopic diagnosis was made, the bone scan was normal. The use of radioisotope scintigraphy is recommended in the problem knee presenting with anterior pain.