The knee cap (patella) moves up and down along a groove in the femur every time the knee bends or straightens. There are a number of different structures that can cause anterior knee pain, however the problem generally stems from muscle weakness or imbalance around the hip and knee.
What Is It
Muscle weakness and tissue tightness can cause the knee cap to track poorly resulting in pain behind the knee cap and poor biomechanics can place excessive load on the soft tissue around the knee cap, leading to pain.
Anterior knee pain syndrome often occurs in individuals who run or routinely engage in other repetitive activities involving their legs.
The condition is usually characterised by a dull achy pain in the front of the knee. Pain tends to be increased with walking up and down stairs and may be associated with clicking or grinding.
Management
The 
initial phase of management is activity modification and avoidance of aggravating activities.
Taping, ice and anti-inflammatory medication or other over the counter pain relievers may help manage the pain but will not help to solve the problem.
Physiotherapy-guided exercise programs are the treatment of choice for anterior knee pain. The goal is usually to improve the biomechanics of the leg by teaching you to use certain muscles, strengthening the weak muscles, and stretching the tight structures surrounding the hip and knee.
This may involve using biofeedback to retrain the sequencing of the quadriceps muscles
