Patellofemoral pain syndrome or Runner’s Knee, is a softening of the cartilage covering the underside of the kneecap and gliding against the thigh. This generally occurs because the kneecap is not tracking as it should. It is supposed to glide easily up and down the leg as it helps the quadriceps muscles achieve good mechanical leverage. But with excess pronation, the patella or kneecap deviates to the inside.
One of the most common causes for this condition is weakness of the Gluteus Maximus and Gluteus Medius muscles (your “butt” muscles). Weakness of these muscles causes the thigh to fall inwards when under pressure, and this causes a lateral pull on the knee cap which leads to pressure and pain.
Weak Quadriceps muscles (anterior thigh muscles) are also associated with Patellofemoral Pain.
There are many other muscles that can cause a lateral deviation of the knee cap and your physiotherapist assesses the length of each of these muscles.
When this happens, the cartilage that lines the surface underneath the patella erodes or breaks down. Under stress, the cartilage softens and then slowly develops tears and cracks. This can result in a crunching, clicking rough feeling motion of the patella and of course, pain.