Risk factors for pes anserinus tendinitis/bursitis syndrome: a case control study.

BACKGROUND: Pes anserinus tendinitis/bursitis (PATB) is a frequent cause of knee pain. Its predisposing factors are still controversial.
OBJECTIVES: Assess the effect of a set of demographic, clinical, somatometric, and biomechanical factors on the risk for PATB.
METHODS: A case control design was used to evaluate the association between clinically diagnosed PATB and the presence of diabetes; knee osteoarthritis (and its radiographic severity); obesity; knee collateral, and anteroposterior instability; and knee or hindfoot malalignment.
RESULTS: Twenty-two consecutive, incident PATB patients were included; all were females 62.1 +/- 11.5-year-old (limits 45-82). Thirty-eight sex- and age-matched (59.8 +/- 9.4-year-old; P = 0.41) subjects were used as controls; these had asymptomatic osteoporosis (20) and a series of rheumatic syndromes (18). There was no difference in prevalence of diabetes, knee osteoarthritis, obesity, knee instability, varus knee deformity, and hindfoot malalignment between cases and controls. Furthermore, no difference in overall, lateral, medial, and patellofemoral knee osteoarthritis radiographic severity mean score was found between study groups. The presence of valgus knee deformity alone (OR: 5.2; 95% CI: 1.1-25.5), or in combination with collateral instability (OR: 6.0; 95% CI: 1.4-26.0), was identified as associated with PATB.
CONCLUSIONS: Valgus knee deformity, alone or in association with collateral instability, seems to be a risk factor for PATB. No association was found between PATB and some conditions previously reported as predisposing factors such as diabetes, knee osteoarthritis, and obesity. PATB should be kept in mind as a highly probable diagnosis in mature women with medial knee pain and valgus knee deformity.