Osteoporosis and Knee Insufficiency Fracture

Osteoporosis is a systemic bone disease characterized by low bone mass and microarchitectural deterioration of bone tissue with consequent bone fragility and susceptibility to fractures. Fifty percent of women and 20% of men older than 50 y.o. will have an osteoporotic fracture (fragility fracture). Fragility fracture is defined as one that results from a low-energy trauma such as a fall from body height. A previous fracture is an important predictor of a new fracture, especially in the first 5 years after the initial fracture. A second fracture can be particularly devastating if a hip fracture. Approximately 25% of individuals with hip fracture die in five years and only half of them recover the pre-fracture status, meaning loss of ambulation ability and independence in domestic activities. In addition, fragility fractures generate significant cost to the health system - the annual cost of osteoporotic fractures in patients older than 50 years in the United States is estimated at 1.3 billion dollar.

Low bone mineral density, measured by bone densitometry, as well as a previous osteoporotic fracture, are the two major risk factors for the occurrence of a new fracture. A crucial observation is that fracture attracts fracture, ie, individuals who had a fragility fracture are twice as likely to suffer a second fracture and half of patients with a hip fracture had previously broken another bone. Therefore, a more rational approach currently used to minimize the costs of health care more effectively and in a short time uses firstly the strategy of preventing the occurrence of secondary fracture, followed by primary prevention strategies. In this context, the correct identification of fragility fractures and the consequent treatment of individuals makes it imperative. However, it is surprising and discouraging the information that despite the huge range of currently available treatments, most patients who sustain a fragility fracture does not receive treatment.

Vertebral fractures and hip has undoubtedly the greatest impact on walking ability of the elderly, and great attention is given to these two types of fracture. Consequently, there are currently insufficient data on the epidemiology and evolution of other fragility fractures, also known as non-vertebral non-hip fracture (NVNH). Among these, distal radius and proximal humerus fractures are the most frequent. There is a type of fracture, however, that is simply ignored by the medical community: the knee insufficiency fracture. The fact that no literature study even hypothesize that this type of fracture may be a fragility fracture may be because, until a few years ago, it was believed that this entity was a osteonecrosis of the knee. The knee insufficiency fracture usually occurs in older individuals and those with knee osteoarthritis. This study therefore aims to evaluate whether a relation between the knee insufficiency fracture and osteoporosis. Moreover, it is expected to find out if this fracture may be defined as a fragility fracture, electing the individuals affected by it to a prophylaxis for the occurrence of new osteoporotic fracture.

BACKGROUND

The knee insufficiency fracture usually occurs in older individuals and those with knee osteoarthritis. Currently no literature study even suggests the hypothesis that this type of fracture may be a fragility fracture. A possible explanation for this information gap could be the fact that, until a few years ago, this entity was believed to be a osteonecrosis of the knee. Only recently it is becoming clear that the cause of pain and marrow bone edema that occur subtly in older individuals is, in fact, a insufficiency fracture. This study therefore aims to evaluate whether a relation between the knee insufficiency fracture and osteoporosis. Moreover, it is expected to find out if this fracture may be defined as a fragility fracture, electing the individuals affected by it to a prophylaxis for the occurrence of new osteoporotic fracture.