Presentations across the ages
The knee is one of the most common joints in the body to be affected by OA. This is due to the large weight-bearing requirement of the knee. When OA affects the knee, the tibiofemoral (TF) and patellofemoral (PF) joints can be involved. A large proportion (40%) of individuals aged over 50 years with knee pain will present with a combined pattern of knee OA (such as TF and PFOA), with isolated PFOA being the second most common radiographic distribution (24%), and a very small proportion (7%) of individuals presenting with isolated TFOA (4%) (see Figure 1).
Figure 1. Radiographic distribution of knee osteoarthritis in individuals over 50 years with knee pain (modified from Duncan et al.)
The large proportion of individuals who demonstrate isolated PFOA has increased the awareness of this condition, which has facilitated further discussion and research regarding PFOA being a precursor to the development of combined knee OA.