What is runner’s knee?
Patellofemoral pain syndrome (PFPS), or more commonly known as ‘runner’s knee’, is anterior knee pain behind or around the patella (knee cap) caused by weight bearing activities that load the patellofemoral (knee) joint. Whilst it is more commonly seen in people above the age of 40, it can affect anyone, with gradual onset occurring as a result of an increased frequency or intensity of training.
What are the symptoms?
Pain occurs during weight-bearing activities on a bent knee, making activities such as a running, walking, climbing and descending stairs, squatting, driving and standing after prolonged periods of sitting painful.
So, what causes it?
Currently, it’s not fully known! The two hypothesised models are mechanical and non-mechanical – however, it’s likely that a mixture of both models can explain experienced pain. Whilst the non-mechanical hypothesis states that the causes are not physical but in fact psychological or social factors that are barriers to recovery, the mechanical model states that pain occurs when the load to a joint exceeds its capacity to withstand it. The cartilage in the patellofemoral joint can’t actually produce pain as it lacks a nerve supply, but excessive loading of the cartilage can increase metabolic activity in the underlying bone which stimulates sensitive pressure receptors in the patella underneath – evoking a pain response. Furthermore, the more bent the knee is, the more load and therefore stress is placed on the joint.
What are the risk factors?
As said before, runner’s knee is more common in adults over the age of 40, but it can occur at any age – it’s also commonly seen in teenagers during periods of rapid growth. Risks include leg length discrepancy and muscle imbalance – for example tightness in the lateral quadricep muscles and hip abductors, or weakness in the hip adductors, as these change the position of the patella and affect how it can bare load. An increase in weight and obesity are also risk factors, and women are two times more likely to get it than men.
What are treatment options?
Whilst an initial period of rest is important, appropriate loading of the patellofemoral joint through exercise is necessary to improve pain and function. Physiotherapy led exercises should begin as soon as possible in order to see results between 6-12 weeks after referral. Education is just as important as exercise for treatment of runner’s knee – learning the correct intensity of exercise to do and the types of activities to avoid is vital to avoid further damage. Pain shouldn’t exceed a 2/10 and shouldn’t increase the following morning after exercise. Rehab is going to be different for everyone and will depend on the severity of symptoms as well as your goals.
To begin with, isolated hip as well as knee exercises will be beneficial, with particular emphasis on the quadricep muscles. Later on, load should be gradually increased with closed chain exercises that target the hip and knee simultaneously being particularly effective, for example single leg squats.
Why is targeting the hip important in runner’s knee?
Patients can display weak hip abductors and external rotators as a result of runner’s knee, therefore performing isolated hip exercises (for example, clams or hip hitches) alongside isolated knee exercises can help reduce symptoms in the early stages of rehab.
Adjuncts to treatment:
For runners it might be worth evaluating your gait – smaller, more frequent steps and a more forefoot striking pattern can reduce the stress on the patellofemoral joint. It also might be beneficial to consider orthotics. Patella bracing alongside is another option, most beneficial in the early stages (up 4 to 12 weeks) however it shouldn’t only be used alone as a treatment.
Summary:
To summarise, runner’s knee is a gradual onset of pain on or around the patella as a result of weight bearing activities that overload the patellofemoral joint. After an initial period of rest, physiotherapy led exercise is vital in order to prevent further damage or pain. To aid recovery, adjuncts such as foot orthotics and patella taping are recommended.
