This condition may also be phrased as either Patellofemoral Joint Syndrome (PFPS), Anterior knee Pain, Patella Pain Syndrome, Runner's Knee, maltracking patellae or Chondromalacia Patellae (however Chondromalacia is pathologically different to PFPS).
Patellofemoral pain syndrome can be defined as a Retro-patellar (behind the knee cap) or Peripatellar (around the knee cap) pain, resulting from physical & biomechanical changes on the Patellofemoral joint (see Fig. 1 below). People that have PPS have anterior knee pain that typically occurs with activity & often worsens when going up/down steps or hills. The pain can occur with sitting for prolonged periods of time & affect one or both knees at the same time (however, usually one).
This condition could potentially be multifactorial (many causes)... meaning it could be muscle (i.e. imbalance/weakness/flexibility); structural (bone/joint) with associated biomechanical (i.e. adverse joint angles & forces directing excess stress) factors... but possibly related to one prime cause i.e. lower limb function (i.e. foot function) or hip function (i.e. weak hip muscles)... which is good, as if you address the primary cause the other issues will gradually resolve.
The potential muscular cause of Patellofemoral pain can be divided into "weakness" & "inflexibility". Weakness of the quadriceps muscles is the most often area of concern... with the Vastus Medialis/Vastus Medialis Oblique being the usual culprit. Weakness of the VMO (Vastus Medialis Oblique) allows the patella to track too far laterally... thus trauma on the underneath surface (see Fig. 1 below). The VMO is difficult to isolate, and may need specific strengthening exercises to strengthen the muscle.
Adductor muscles of the hip play a role in the stability of the pelvis, which can cause an external rotation which may result in compensatory foot pronation. A simple stretch can improve muscular efficiency as well as developing strength in the Glutes (buttock muscle region) to help stabilise hip whilst running can be very effective. Improvements in hip flexion strength combined with increased Iliotibial Band & Iliopsoas flexibility are associated with excellent results in patients with Patellofemoral pain syndrome.
Tight Calve muscles can also lead to compensatory foot pronation, and like the hamstrings they can increase the posterior force on the knee.
- Knee pain is usually felt at the medial area and below.
- Pain is felt after sitting with knee bent.
- Pain may be felt after running down hill or walking down steps.
The patella (kneecap) rests in the femoral groove of the thighbone (femur). Maltracking of the patella irritates the femoral groove and then pain is felt. This maltracking can be caused by the following:
- The patella sitting too high in the femoral groove which may be due to tight quadriceps muscles.
- High arch feet which provide not enough shock absorption.
- Worn cartilage in the knee joint reduces shock absorption.
- Functionally or structurally 'flat feet' can affect the tracking of the patella over the femoral groove due to the act of excess pronation.
- Knock knees can also affect the tracking of the patella over the femoral groove.
- Tight muscles, e.g. hip adductors, quadriceps, hamstrings and calf muscles can affect the tracking of the patella.
- Weak muscles, e.g. quadriceps - in particular the Vastus Medialis branch of the quad. muscle can cause the patella to track out of alignment.
- Running too much on a cambered surface also affects the tracking of the knee joint as well as old, worn out running shoes.
- Inappropriate running shoes for that particular sportsperson / athlete.
- Women can be predisposed to this injury due to their wider pelvic girth.
- Sudden increase in running mileage and / or hill training.
It can sometimes be vague as to which is the root/primary cause... a bit like the chicken/egg scenario if you like (what contributed to what first), but if you do not control a present potential pathologic foot function (providing one exists), the outcomes will rarely hold just by focusing on the hip (i.e. Glutes) & Quad (i.e. Vastus Medialis) musculature alone.
- Running should be decreased to reduce stress and encourage healing.
- Avoid downhill running.
- Avoid exercises where the knee is bent.
- Do straight leg lefts (strengthen the quad. muscle group).
- Stretch tight posterior muscles, calf muscles and hamstrings.
- Do not wear old, worn-out shoes.
- Orthotics may be required if there is a biomechanical condition, e.g. excess pronation (rotation of lower limb).
- Strapping: to help keep the Patella in a better position. The following instructions is of one technique which can be an effective way to do this - Patella Strap (link).