[Idiopathic painful patella syndrome: an etiopathogenic hypothesis]

A prospective arthroscopic study on 140 knees to discover the etiopathogenic mechanism responsible for idiopathic patellar syndrome (IPS) was carried out.

Patients were grouped into two categories: One group with idiopathic patellar syndrome (76 patients, 53 male and 23 female), the other group (control group) presenting no patellar pathology in clinical, radiological and arthroscopic examinations (64 patients, 55 male and 9 female). The author analyzed the statistical differences using 9 clinical and morphometric parameters in the IPS group and the control group. The morphometric index PTO/LNPL (PTO: distance between the medial upper end of the tibia and the inferior border of the pes anserinus. LNPL: width of medial tibial surface) seems to be a valid reference index (p = 0) for the diagnosis of IPSI caused by internal rotatory muscle deficiency.

The X2 test showed significative correlation (p < 0.05) between sex and IPS. The incidence of IPS was 1/1 in males and 2.5/1 in females. The PTO/LNPL value in this syndrome was higher than 1.1. No patient in the IPS group had spontaneous recovery, nevertheless, 86.8 per cent of patients has a good result after 6 months of physical therapy of the internal rotatory muscles.

The high distance between the medial upper end of the tibia and the inferior border of the pes anserinus in knees with IPS as well as the good results obtained by physical therapy of the internal rotatory muscles leads the author to suggest a new etiopathogenic mechanism for IPS: some idiopathic patellar syndromes may be caused by an isolated internal rotatory muscle deficiency of the leg.

The author concludes with two therapeutic suggestions: 1. physical therapy of the internal rotatory muscles should be used in patellar syndromes caused by deficiency of internal rotatory muscles. 2. Methods which sacrifice internal rotatory muscles in knee ligament surgery should be avoided as these could lead to a possible patellar syndrome by deficiency of internal rotatory muscles.