I have not really heard of the patella swelling before. I have seen the capsule swell in numerous cases, the various patella bursae swell as well but not the bone. Chondromalacia Patellae (or more simply patellofemoral pain) isoften one where the aggravating factors (increased Q angle etc) need to be assessed and addressed. Here's a little summary of chondromalacia.
You could also get a tumor in the patella that could cause swelling such as in Patellar metastasis from a malignant melanoma. Again investigations would be needed first. Perhaps you can provide a bit more information about the case history, signs and symptoms so we can provide some more educated advise or ideas.
Chondromalacia patellae is a pathological diagnosis which includes softening and degeneration of patellar articular cartilage. There are four grades of disease severity, ranging from softening and blister-like swelling of the patellar cartilage in grades 1 and 2 respectively to surface irregularity and areas of thinning in grade 3 and ulceration and exposure of subchondral bone in grade 4 disease. The aetiology of chondromalacia patellae is unclear. It has been attributed to predisposing factors such as patellar malalignment and trauma, but many cases are idiopathic. The diagnosis may be confirmed at arthroscopy when changes in cartilage can be directly visualised. However, it is not always thought necessary to carry out an invasive procedure such as arthroscopy to diagnose an often benign and self limiting condition.