The patella, or kneecap, sits within with the trochlear groove at the end of the femur; our knee is a hinge joint so it's really only designed to move and bend in a single direction. Several forces act on the kneecap to provide stability and keep your knee tracking properly. But when pain is felt around and underneath the kneecap, and exacerbated with activity often times it's a case of patellofemoral pain syndrome (PFPS) or "runner's knee".
What exactly causes PFPS?
When the knee bends and straightens, the patella glides within the trochlear groove; PFPS occurs as a result of the patella tracking abnormally within this groove. This causes abnormal stress on the tissues within and surrounding the joint, eventually leading to pain.
Often irritated with activities such as when climbing and descending stairs, running, and squatting. The most common symptom of patellofemoral pain syndrome is pain underneath and around the kneecap. It may be a sharp pain or a dull ache. Prolonged sitting can also be a trigger due to increased pressure between the kneecap and femur when the knee is flexed in a seated position. A clicking or grinding feeling may also be present.
Potential Causes & Their Treatments
Often times the cause of PFPS is multifactorial; repetitive impact is often a contributing factor coupled with underlying structural factors; here are a few common causes:
Muscular Tightness or Weakness:
Weakness of the quadriceps muscles, specifically the inner most quadriceps muscle since often times it's far weaker than the outer quadriceps. The knee cap is embedded into the quadriceps tendon and the quadriceps muscles plays a significant role in stabilizing, aligning, and controlling movement of the knee cap. For this reason quadriceps strengthening is commonly recommended.
Tight hamstrings can also be a contributing factor. Your hamstrings are one of the major muscles used to bend the knee; a tight hamstring can increase the pressure placed between the kneecap and femur.
Hip, hamstring, calf, quadriceps, and iliotibial band stretching may also be important. Glute weakness can also be a contributing factor to PFPS.
A high arch often provides less shock absorption for the leg when it strikes the ground. This places more stress on the knee especially doing high impact activities like running. Proper footwear such as cushioned running shoe and an arch support to provide a broader base of support can lessen the impact absorbed at the knee. Worn out shoes or improper footwear can also be a culprit.
Excessive foot pronation or arches that collapse cause a compensatory internal rotation of the shin bone, this can upset the tracking of the knee cap by compromising the position of the knee. The premise behind using arch supports is to raise the arch and limit the rotation of the shin bone better aligning the kneecap in the trochlear groove of the femur.
Presenting with a large Q-angle (wide hips), knock-knees, and/or squinting knee caps can all be contributing factors to patellofemoral pain syndrome, for this reason females are more prone to this type of knee injury.
Repetitive physical activity such as running, jumping, and squatting, puts repetitive stress on your knees. A sudden increase in training intensity or frequency, too much uphill/downhill running, a change of playing surface or footwear, and improper technique can all be contributing factors to PFPS. A reduction in training volume and intensity, a change to softer, flatter terrain, as well as a focus on technical improvement can help all lessen the stress placed on your knees and give the injured tissue time to heal.
Patellofemoral pain syndrome often is multifactorial and often stems from factors both above and below the knee. Orthotics may be utilized to correct faulty mechanics and help manage symptoms.