There are countless jokes told about the supposed lack of general medical knowledge held by the typical orthopaedic surgeon. Perhaps studies such as this may slowly erode that source of humor.

One would have to be isolated from all lay press to be ignorant of the association between hyperlipidemia and heart disease. Less known is the correlation with orthopaedic conditions, specifically problems of the shoulder. For instance, the data on the relationship between hypercholesterolemia and rotator cuff tear have been mixed, with some studies recognizing a connection and others failing to demonstrate a link. In an animal model, hypercholesterolemia has been shown to negatively affect the mechanical properties of the rotator cuff tendon.

Similarly, there has been some controversy with regard to the relationship between hypercholesterolemia and hyperlipidemia with frozen shoulder; some studies have suggested a strong association but others have not found any significant relationship. Some of these differences may lie in which lipoproteins were measured and by what testing technique. Alternatively, the different conclusions may simply reflect differences in the patient populations. In their study, Dr. Sung and colleagues observed patients from a single practice, with an age and sex-matched control group, to attempt to rectify these differences. Also, in contrast with prior studies, the authors excluded patients with diabetes and thyroid abnormalities. Finally, the cholesterol and lipoprotein testing protocol was thorough. These authors demonstrated that total cholesterol, low-density lipoprotein, and high-density lipoprotein levels are significantly associated with idiopathic frozen shoulder. Similar associations were found between certain inflammatory lipoproteinemias. No connection was found with hypertriglyceridemia.

Case-control studies such as this clearly have inherent methodological limits that restrict drawing any conclusions other than associations. For instance, there may be dramatic differences between the case and control populations other than their serum lipid profile. Did the two patient populations have similar dietary and exercise habits? What percentage of the patients in each group was taking statin medications? We know that the use of certain medications is associated with frozen shoulder. Was there an association with the use of statin medications and the development of frozen shoulder? More importantly, was normalizing the serum cholesterol level by use of statin medications associated with a lower risk of developing frozen shoulder?