Patellofemoral Pain Syndrome (PFPS) also known as runners knee is a generic term used to describe pain at the front of the knee which comes on gradually with symptoms increasing over a period of time.
It is sometimes also called anterior knee pain and occurs when the patella does not move or 'track' in a correct fashion when the knee is being bent and straightened.
This can lead to damage to the cartilage on the underside of the patella itself resulting in knee pain and inflammation. This injury is quite common in people who do a lot of sport, in particular adolescent girls.
Symptoms of Patellofemoral Syndrome
- Aching pain in the knee joint, particularly at the front, around and under the patella.
- Tenderness along the inside border of the kneecap.
- Swelling sometimes occurs after activity.
- Pain is often worst when walking up or down hills or stairs.
- A clicking or cracking sound may be present on bending the knee.
- Sitting for long periods may be uncomfortable. This is known as the theatre sign or movie-goers knee.
- Wasting (atrophy) of the quadriceps muscles in prolonged cases.
- A Q-angle greater than 18 to 20 degrees.
- Tight muscles including calf muscles, hamstrings, quadriceps (especially vastus lateralis on the outside) and iliotibial band.
Causes of Patellofemoral Pain Syndrome?
When bending and straightening the knee, several muscles surrounding the joint act together to cause the patella to run in a straight line within the intercondylar groove, formed by the Femur and Tibia. If any of the structures are particularly tight or weak, this causes an imbalance which can result in the patella mal-tracking.
The most common example of this is when the lateral (outer) structures of the knee including the vastus lateralis, iliotibial band and lateral retinaculum are tight and the vastus medialis oblique (VMO) muscle on the inside of the knee is weak. This results in the patella moving too far laterally (to the outside) as the tight lateral structures pull it across and the medial (inner) muscles are not strong enough to control this force.
Patellofemoral knee pain can also occur following a knee injury, if the muscles of the quadriceps (especially VMO) become inhibited or considerably weakened. There are other factors which can contribute to the development of this injury:
- Overloading - Bending the knee increases the pressure between the patella and the femur. Thus sports such as running, where repeated weight-bearing occurs, may result in PFPS.
- Pronating Feet - Pronating or 'flat' feet lead to an increased biomechanical stress on the knee joint. This may affect the alignment of the patella particularly during movement.
- Q-angle - Some people have a larger than normal femoral angle (known as the Q-angle) resulting in a 'knock-kneed' appearance (genu valgum). When the person straightens their leg when weight bearing, the patella will be forced to the outside of the knee. With repeated bending and loading, this motion may lead to damage of the underlying structures and cause pain. A larger Q angle is common in women due to their wider pelvis. This is why more women suffer with this condition than men. Strengthening the abductors (Gluteus Medius, Minimus and Tensor Fasciae Latae) and lateral rotators (Gluteus Medius and Maximus) of the hip can be beneficial when a wide Q angle is thought to be a contributing factor.
PFPS is often confused with another condition known as Chondromalacia Patellae (CMP). This is damage to the cartilage which lines the underside of the knee cap. CMP can be a result of PFPS, although it can also occur independently, usually due to damage from an impact.
Who is Most at Risk From Patellofemoral Syndrome?
- You are more prone to this if you have a small kneecap or one that sticks out If your feet roll in or pronate.
- If you suffer with tight muscles.
- If you have weak quadriceps muscles.
- Athletes who do a lot of long distance running or hill running.
- Those who have had a previous knee dislocation
Runners Knee Treatment
What can the athlete do?
- Apply RICE (Rest, ice compression and elevation) after activity. This will help reduce pain and swelling.
- Rest until there is no pain (this is very important).
- Wear a runners knee brace or support which will help control patella tracking. These will usually have a hole in the middle for the kneecap and often straps which are pulled across the knee applying support to the patella.
- See a sports injury professional who can advise on treatment and rehabilitation.
What can a Sports Injury Professional do?
- Prescribe anti-inflammatory medication e.g. ibuprofen.
- Prescribe a comprehensive rehabilitation programme in conjunction with taping techniques.
- Investigate the possibility of a synovial plica.
- Use massage to loosen tight structures.
- Advise on patellofemoral pain syndrome exercises especially for the vastus medialis muscle on the inside of the knee and stretching exercises for the outside of the knee.
- Perform gait analysis to determine if you overpronate
- Provide orthotic foot supports if necessary.
- Operate in chronic cases to release the tight lateral structures.
PFPS can be caused by a number of biomechanical problems, starting with the feet. Ensure that you have the right running shoes for your style.