What is Patellofemoral Syndrome (Runner’s Knee)?
Patellofemoral syndrome (PFS), also known as patellofemoral pain syndrome (PFPS) or “runner’s knee,” is a common reason people experience pain in the front of the knee. People usually feel this pain when they bend their knee to do activities like running, climbing stairs, or squatting. PFS is typically diagnosed once doctors have ruled out other conditions that might be causing knee pain. Most of the time, the symptoms of PFS can be managed effectively with non-surgical treatments. However, in some rare cases, the pain might continue despite treatment and can last for many years.
What Causes Patellofemoral Syndrome (Runner’s Knee)?
The exact cause of patellofemoral syndrome is not entirely known, but it’s likely due to multiple factors and related to how one trains. The condition could involve six different areas of the knee’s anatomy: the bone underneath the cartilage, the tissue lining the joint, the band of tissue around the knee, the skin, nerves, and muscle.
Four notable factors contributing to this syndrome are: misalignment of the knee/ kneecap, muscle imbalance in the legs, excessive use/strain, and injury. It seems that overuse is commonly leading to the syndrome. For example, athletes who focus on one sport are 1.5 times more at risk of the condition compared to athletes who play multiple sports.
Misalignment and Muscle Imbalance
The kneecap joint depends on a careful balance of steady (‘static’) and moving (‘dynamic’) components in the entire leg as the kneecap glides in a groove at the end of the thigh bone. Steady components include differences in leg length, abnormal foot structure, tight hamstrings and hip muscles, bone deformities, knee grove shape. Dynamic components include muscle weakness, the force from the ground as we move, and too much or too little foot movement when walking or running.
Numerous studies suggest that a weakening of the hip muscles that pull the legs apart might be a significant factor. Indeed, one study found that women runners with larger hip angles were at a higher risk for developing the syndrome.
Overactivity and Overload
Interestingly, many patients with patellofemoral syndrome don’t show any signs of misalignment. Often, they describe overloading their kneecap’s joint, leading to the condition. For example, increased activity, running longer distances, or overworking can contribute to the syndrome. Higher body mass index (a measure of body fat), previous fitness levels, and previous exercise routines can also increase the syndrome’s risk.
Trauma
Injuries to the kneecap area, whether direct or indirect, can harm the structures and lead to patellofemoral syndrome.
Though the above factors contribute to the syndrome, most professionals would agree the syndrome’s appearance is rarely due to a single factor.
Risk Factors and Frequency for Patellofemoral Syndrome (Runner’s Knee)
Patellofemoral syndrome is a common knee condition, especially among active individuals, where it may represent up to 40% of knee problems seen in sports medicine. The exact number of cases is unknown, but it’s clear that it affects more women than men, almost at a 2:1 ratio. It’s most commonly seen in teenagers and adults in their twenties and thirties. In fact, over 20% of adolescents experience this condition.
- Patellofemoral syndrome is a frequent knee issue, particularly in active people.
- It makes up 25% to 40% of all knee issues in a sports medicine clinic.
- It’s more prevalent in women, with nearly twice as many women affected compared to men.
- Most commonly, it arises in adolescents and adults in their twenties and thirties.
- More than 20% of teenagers have this condition.
Signs and Symptoms of Patellofemoral Syndrome (Runner’s Knee)
Patellofemoral syndrome (PFS) is a knee condition that requires a thorough history and physical examination for diagnosis. People with this condition could have symptoms in one or both knees, and the symptoms range from gradual to sudden. Typical problems include pain worsening when squatting, running, sitting for a long time, or using stairs. Usually, the pain is pretty vague; it feels like it’s behind or around the kneecap, and it can range from a dull to a sharp ache. Some people say their knee feels like it’s giving way or catching, which could be signs of issues with ligaments or the interior structure of the knee. Key details to ask about include whether the person has ever injured their knee, any previous surgery, or any excessive use activity.
During the physical check-up, you’ll start with a general look-over of the person and their affected knee. You might consider factors like their weight, age, any muscle abnormalities, like shrinking of the vastus medialis, or any redness on the joint that could mean infection. Feeling the joint can help identify if the quadriceps or patellar tendons are sore, while also checking for fluid build-up or warmth. Testing muscle strength can be useful, particularly for weaknesses in the hip abductors or quadriceps. Any differences between the affected and unaffected sides are worth noting because PFS can cause weakness. Also, check the range of movement of the impacted knee. Lastly, also examine the hip on the same side as it’s possible that knee pain could be referred from there.
There are various special tests that can be done, but many aren’t specific for PFS. A study found that tests for patellar tilt, active instability, high kneecap, and apprehension had a low sensitivity around 50%, specificity varied between 72% and 100%. However, the study identified some characteristics specific to PFS: an increased angle of the quadriceps, tenderness on the sides of the kneecap, crepitus (a crunching or popping sound) in the kneecap, squinting patella, and reduced mobility of the patella. Measuring the popliteal angle, which checks the flexibility of the hamstring muscles, has been linked with PFS development. Tight hamstrings put extra pressure on the patellofemoral joint which raises the chance of developing PFS.
Testing for Patellofemoral Syndrome (Runner’s Knee)
Patellofemoral pain syndrome, also known as ‘Runner’s Knee’, is often diagnosed just through assessing your symptoms and medical history – this is called a clinical diagnosis. Doctors don’t usually perform further tests, such as a plain radiograph (also known as an X-ray), unless your symptoms don’t improve after a month or two of basic treatment.
X-rays aren’t always that helpful in these cases because it can be hard to spot the difference between the knee that hurts and the one that doesn’t. If basic treatment doesn’t help, doctors may use imaging tests not to confirm patellofemoral pain syndrome, but to rule out other conditions that could be causing similar pain. These could include a bipartite patella (where the kneecap is split into two parts), osteoarthritis, loose bodies (small loose fragments of bone or cartilage), or a hidden fracture.
Advanced imaging methods such as Magnetic Resonance Imaging (MRI), musculoskeletal ultrasound (US), and Computed Tomography (CT) scans are not normally used. These would be used, like standard imaging, to look for signs of different conditions that could explain your symptoms.
Treatment Options for Patellofemoral Syndrome (Runner’s Knee)
Treatment for patellofemoral syndrome, a condition causing knee pain, usually focuses on managing the pain, improving the movement of the kneecap, and getting the person back to their usual level of activity. This treatment can be split into two main stages – the initial acute stage, and the later recovery phase.
During the initial stage, the person might be advised to change their physical activities somehow, to use non-steroidal anti-inflammatory drugs (NSAIDs) like naproxen to help reduce pain, and to use simple therapies such as ice packs. NSAIDs have been found to be more effective at reducing pain than aspirin or placebo, but are generally not recommended for long-term use. Note that other treatment methods, such as ultrasound therapy or electrical stimulation, haven’t been shown to improve the symptoms of patellofemoral syndrome.
After the initial treatment, the focus shifts to the recovery phase, where the aim is to resolve the underlying issues that likely led to the condition in the first place. This phase often involves a mix of exercises designed to strengthen the lower body and improve mobility and function. If these exercises cause pain, other treatments can be used alongside them, like patellar taping, a technique where tape is applied to the knee to provide support. Studies have shown that when used with physical therapy, patellar taping can further reduce pain. However, this treatment may be less effective for people with a higher body mass index (BMI).
It’s important to remember that treatment should be personalised and aimed at correcting each person’s specific dysfunction. Additionally, referring the patient for orthopedic surgery is not typically recommended and is seen as a last resort. Non-surgical treatments should generally be tried for at least 24 months before considering surgical options.
What else can Patellofemoral Syndrome (Runner’s Knee) be?
When a patient has Patellofemoral Syndrome (PFS), the causes can come from various areas of the body. Doctors need to consider many possible conditions, including issues related to six specific anatomical areas. These are:
- Patellofemoral Osteoarthritis (OA)
- Osgood Schlatter’s disease
- Plica
- Bursitis (either prepatellar or Hoffa’s)
- Saphenous neuritis
- Quadriceps tendinopathy
- Patellar tendinopathy
- Pain referred from the hip or back
Because of these various possibilities, doctors need to take a thorough medical history and perform a comprehensive physical examination of the patient. This helps them identify potential risk factors and, in turn, provide the most effective treatment for the patient’s condition.
What to expect with Patellofemoral Syndrome (Runner’s Knee)
Patellofemoral syndrome typically has a good prognosis. However, about 40% of patients diagnosed with this condition might still experience symptoms a year after initial treatment. A study showed that seven years after treatment, nearly 85% of patients who followed a home exercise routine reported successful results.
However, factors like a hypermobile patella (a condition where the kneecap easily moves out of place), older age, and symptoms appearing in both knees can negatively impact long-term recovery.
Possible Complications When Diagnosed with Patellofemoral Syndrome (Runner’s Knee)
One potential problem that may arise from Patellofemoral Syndrome (PFS) is the onset of a common joint condition called osteoarthritis. This specifically affects the knee, due to improper movement of the kneecap, and might result in long-term pain. Another downside is that some people might have to quit doing things they love because those activities bring them pain.
Common Complications:
- Development of osteoarthritis in the knee
- Long-term pain,
- Having to stop doing certain activities due to pain
Preventing Patellofemoral Syndrome (Runner’s Knee)
Patients should be informed about their diagnosis, what caused it, and the available treatment options. They should also receive a list of exercises that they can practice at home, or they may be recommended to a physical therapy program where they will be trained on how to perform these exercises properly. It’s also advised that patients take time to rest, consume NSAIDs (Non-Steroidal Anti-Inflammatory Drugs), and apply ice as often as possible for the first 2 to 3 weeks. These steps help in managing pain and aiding recovery.
