A: The majority of patients with primary knee osteoarthritis show early onset of wear or damage between the patella and femoral joint, called patellofemoral arthritis, commonly known as “chondromalacia patellae”. This is because the patellofemoral joint surface is under the most stress when walking up and down stairs or squatting, so there will be pain or walking “weak legs”. When these symptoms occur, you should exercise your quadriceps and avoid excessive up and down stairs, stances and squats to reduce the pressure on the patellofemoral joint surface. If the pain is severe, you should take painkillers or go to the hospital.