Spring is a great time for outdoor running with the melting snow and rising temperatures however runners should be cautious when switching from indoor to outdoor surfaces. Increased mileage and change in footing as runners move outdoors increases the risk of developing an injury. One of the most common complaints is knee pain, which can be a symptom of multiple injuries. The first part of our running injury series will focus on one of those injuries; patellofemoral pain syndrome, commonly known as runner’s knee.
Runner’s knee is an umbrella term used to describe anterior knee pain, pain behind or pain around the kneecap mainly as a result of misalignment of the patella and muscle imbalances. Symptoms begin with a gradual onset of dull aching pain and swelling that usually starts during a run. Over time any running, descending stairs, kneeling and squatting become painful from the resulting stress on the patellofemoral joint. Sitting for prolonged periods with the knee flexed will also be painful, and grinding noises called crepitus may be present.
There are a number of contributing factors to the development of runner’s knee, which can make it challenging to treat. Any activity that increases the stress on the patellofemoral joint can contribute to the development of runner’s knee as the surrounding tissues become irritated and painful. This can occur with new runners or those who increase the intensity, speed and duration of their runs. Additionally, downhill running and running on firm surfaces, such as asphalt and concrete, increase the stress on the patellofemoral joint.
Muscle tightness, weakness or anatomical/biomechanical abnormalities in the leg can alter the distribution of force through the knee and affect the alignment and tracking of the patella, placing increased stress on the patellofemoral joint. The main areas to consider are the quadriceps muscle, gluteus medius muscle, gluteus maximus muscle, and iliotibial band.
One key muscle is the quadriceps. The four heads of the quadriceps femoris converge into a single tendon that inserts on the patella and continues through the patellar ligament to insert on the tibia, functioning to extend the leg at the knee and stabilize the hip. Another key muscle is the gluteus medius that originates on the hip and inserts on the femur, which also helps to stabilize the pelvis when the opposite leg is raised. If the quadriceps and gluteus medius muscles are weak and unable to stabilize the hip during running, normal force distribution throughout the knee and leg will be altered.
If the gluteus maximus muscle is tight, it will externally rotate the thigh, altering its angle relative to the lower leg, which will disrupt normal tracking of the patella. The iliotibial band runs down the outside of the thigh and inserts on the tibia, but it also connects to the patella via patellar tendons. Tightness of the iliotibial band can pull the patella slightly laterally, increasing stress on the patellofemoral joint.
Additionally, any tight muscles around the knee can affect movement of the patella, potentially causing excessive stress on the joint. Over pronation of the feet causes the leg to drop and internally rotate with each step, which can alter normal movement of the patella.
The first step in rehabilitation is to determine all of the underlying and contributing factors. A detailed physiotherapy assessment will reveal areas of tightness and weakness, as well as any anatomical and biomechanical factors. Tight muscles will be addressed with education on correct stretching techniques and a personalized stretching program. Specific strengthening of weak muscles and correction of biomechanical changes will be addressed with a progression of strengthening exercises from isometric to dynamic, and eventually functional and activity specific. Any hip, pelvis or lower back restrictions will be treated through joint mobilizations. It is important to consider more than just the structures immediately surrounding the knee because stiffness in these other joints will cause biomechanical changes that become more evident with running, and may cause the condition to reoccur if these areas are not addressed. Corrective taping to keep the patella in proper alignment can relieve pain and help to prevent aggravation of the condition during a gradual return to running. Evaluation and correction of footwear, gait and running stride will help to improve running form and improve biomechanics during running.
The goal following physiotherapy treatment is for a pain and injury free return to the previous level of running. Maintenance or improvement of hip, lower extremity and trunk flexibility as well as strength will not only prevent a reoccurrence of runner’s knee, but also protect against other running injuries. Stay tuned for part 2 of our running injuries series to learn about a different cause of knee pain; iliotibial band friction syndrome.