Welcome, Anonymous, and thanks for your post.
We're sorry to hear you fell on your kneecap and it's difficult to straighten your knee.It would be best to see your medical provider as soon as you can and not let this linger and worsen.Your provider will do a physical exam and order xrays to determine exactly what's going on. You may or may not have A patellar fracture which is a break in the patella, or kneecap, the small bone that sits at the front of your knee. The patella acts as a shield for your knee joint and is vulnerable to fracture if you fall directly onto your knee. The patella can fracture in many ways. A fracture may be a simple, clean, two-piece break or the bone can break into many pieces.A patellar fracture is a serious injury that can make it difficult or even impossible to straighten your knee or walk.
According to the Academy of Orthopedic surgeons Some simple patellar fractures can be treated by wearing a cast or splint until the bone heals. In some patellar fractures, however, the pieces of bone move out of place when the injury occurs. For these more complicated fractures, surgery is needed to restore and stabilize the kneecap and allow for the return of function.
Until you are able to get medical attention please take extra care in order to avoid any further injury. We hope you are back on your feet soon. Best, Pat