femoropatellar osteoarthritis
Femoropatellar osteoarthritis (also known as patellofemoral or retropatellar osteoarthritis) is the wear of cartilage in the joint between the kneecap (patella) and the groove of the thigh bone (trochlea). Typical symptoms include pain at the front of the knee, pain when climbing stairs (especially when descending) or after sitting for extended periods with the legs bent, often accompanied by a grating or crunching sensation.