Knee pain around the kneecap

Information on kneecap pain (patellofemoral pain syndrome)







What are kneecap complaints (Patellofemoral pain syndrome)?

The knee consists of two pieces of bone, the tibia (tibia) and femur (femur). The bone at the front of the knee is the kneecap (patella). This is the largest sesamoid bone in the body. The kneecap connects the thigh muscles to the tibia. The function and main task of the kneecap is to optimally transfer the force of the thigh muscles to properly extend the knee.

During bending and stretching, the kneecap moves through a groove in the upper leg (the trochlea femoris). We call this the patellofemoral joint. The kneecap moves stably through the groove by controlling upper leg muscles and a number of ligaments (medial patellofemoral ligament (MPFL) and lateral patellofemoral ligament (LPFL)).

During running, the force in the patellofemoral joint can reach four to six times the body weight. The high peak load on the patellofemoral joint makes it somewhat susceptible to overuse. There are several names to describe pain around the kneecap. Ventral knee pain, patellofemoral pain syndrome, patellofemoral chondropathy and patellofemoral dysfunction. Previously, these pains in teenagers were referred to as growing pains or cartilage damage. Often the cartilage, especially in teenagers, was found to be just fine.


In whom does it occur?

Patellofemoral knee pain is more common in girls than in boys. You also see the symptoms mostly in athletes with unilateral loading (cycling, skating and running) and in people who do not adequately maintain their muscle system.

Anyone can suffer from kneecap complaints regardless of gender, age, health or sport. Nevertheless, two groups can be distinguished in whom the complaints are most common:

Girls and boys in growth (12-16 years). The whole body must adapt to the growth that girls and boys are experiencing. This also requires adaptation in the way of movement, motor control, muscle strength, etc. As a result, the patellofemoral joint can be less controlled and overuse can occur.

Elderly (>45 years old) where cartilage damage or osteoarthritis has developed on the back of the patella. This makes the gliding surface less smooth, bumpy and more easily irritated. This promotes patellofemoral pain. In this case, we also talk about a retropatellar chondropathy.

patellofemoral knee complaints in figures:

About 23% of the Dutch population has complaints around the kneecap. Of these, 29% are adolescents and of these, about 70% are girls or women.

Where does the pain come from?

The patellofemoral joint consists of a kneecap covered with cartilage, a patella, and quadriceps tendon, a retinaculum, fat body of hoffa, synovium and the bone. All of these structures except cartilage contain pain sensors.

This is a tendon between the thigh muscle and the knee capsule. When irritated, there can be an increased ingrowth of free nerve endings here, causing faster pain symptoms. This structure becomes pinched when the knee is fully extended.

Fat Body of Hoffa:
This is a body of fat under the patellar tendon at the front of the knee. This is one of the most sensitive structures of the knee joint. When overstimulated or inflamed, it can cause pain. For example, after a fall directly on the knee or keyhole surgery where the incision for surgery passes through Hoffa's fat body.

This is synovial fluid and is light as a surface layer over the bones in joints. This fluid is the lubricant of a joint and allows the joint to move properly. It also acts as a shock absorber and provides nutrients to the underlying bone. This synovium is also abundant with free nerve endings so an irritation of this can quickly lead to pain symptoms.

Subchondral bone:
This is the bone directly beneath the articular cartilage. Subchondral bone is equipped with free nerve endings and therefore can cause pain when overloaded. When the protective cartilage is damaged, the subchondral bone experiences peak stress, this can cause over-stimulation.

What is the cause for kneecap pain?

While running, climbing stairs and squatting, there are large forces that need to be processed by the body. Our body is good at this, but due to repetitive high loads and muscle weakness, for example, the forces may not be processed sufficiently efficiently.

Disrupted alignment:
During movement, the kneecap slides from top to bottom through the groove in the upper leg (trochlea femoris). This is more or less a vertical line. Ideally, the force runs parallel to this vertical line ( Q angle) straight through the hip, knee and second ray of the foot/toes. If this does not happen because, for example, there is a weakness of the muscles around the hip or collapsed foot (flat foot), the kneecap must angle to follow the groove (trochlea). This can cause irritation of the patellofemoral joint. High loads, such as sports, can accelerate this process. Insufficient rest between sports or provocative activities can also result in pain symptoms.

The causes of misalignment are diverse.

  • Posture: x-legged or overstretched
  • Mobility: a stiff hip or big toe.
  • Foot: sagging foot arch or a stiff big toe
  • Strength: decreased strength of the thigh and trunk muscles
  • Control: control of muscle systems.

From the causes, you can see that not only the structures around the knee affect the position of the knee but the total chain of motion must be analyzed.

The most common cause of kneecap pain is overuse. Repetitive loading during sports, cycling and running can irritate the kneecap. A disturbed alignment usually underlies this. If you continue to irritate the joint by not taking enough rest, the pain can persist and become sensitive even with less intense loading.

Other forms of overuse include sitting on the knees a lot, squatting, deep squats, climbing stairs and cycling at high resistance.

Cartilage wear:
The medical term for cartilage-related kneecap pain is retropatellar chondropathy.
People over the age of 45 have a high risk of developing wear and tear behind the kneecap. Young people can develop a cartilage defect due to, for example, kneecap luxation.
As the cartilage surface wears down, the sliding surface becomes less smooth and bumpy. An abrasive sound may be heard during bending and stretching. The sound is considered distracting and annoying, but it is not harmful. A thinner layer of cartilage cannot handle peak loads as well, which can cause pain symptoms.

Fall on knee:
A fall directly on the knee can damage, irritate or inflame the structures within the patellofemoral system. As a result, the free nerve endings of various structures can become overstimulated and cause pain.

Patellofemoral instability:
The kneecap must be able to guide stably through the groove of the femur. After a patellar (sub) luxation, the ligaments of the kneecap become stretched and it is less well held in place. In addition to passive structures, the kneecap is also actively controlled by muscles. With poor motor control, the kneecap no longer guides stably through the groove of the upper leg. With patellofemoral instability, the structures in the patellofemoral system become easily overstimulated resulting in pain.

Low back involvement:
The active structures, such as muscles, around the knee are controlled by nerves. These nerves run down from the brain through the spinal cord in the spine. The structures around the knee are connected to nerves from the low back. This spot in in the low back is a switching point, a kind of meter box where several nerves come together to run collectively down the spine. This is a crucial switching point.

People with patellofemoral complaints sometimes also have back problems. Disruptions or stiffness in the "knee" segment of the low back affects knee complaints and visa versa. When treating knee complaints, it is important to analyze the low back as well. Treating the low back also indirectly treats the knee. The overworked muscles around the knee relax and the registration of pain in the knee can normalize.

With patellofemoral complaints, pain is present. Pain acts as an alarm system for your body. If you have pain in the knee, you put less strain on it. To some extent, this is a useful system as long as the pain stimulus is a response to an impending situation for injury. With kneecap pain, it is common for pain to remain present with no chance of damage. Prolonged pain stimuli can disrupt the alarm system. The alarm system is over-tuned and has become hypersensitive as a result. An (innocent) stimulus triggers a pain response.

So there is a sensation of pain, only the stimulus leading to the pain is not necessarily a sign of impending damage. The stimulus is misjudged and not properly controlled by the spinal cord. This misalignment is reinforced and maintained by a vicious cycle. Because of the pain, you start to spare the knee. Free nerve endings in the knee become hypersensitive to protect the knee. People start worrying more and more at this stage and the focus becomes on the pain. The only proper response is to spare the knee, but this is counterproductive. The alarm system must be recalibrated. Here attention to pain perception, explanation of the complaint and the segment of the back that is in connection with the knee is important.

 Pain is multifactorial:
As you have read, pain is a complex system to understand properly. Pain is primarily a response to a noxious stimulus or consequence of damaged tissue. Pain also depends on how sharply the alarm system is tuned and how you deal with the pain symptoms. It does not stop here, however. Pain appears to be influenced by even more factors. Consider, for example, stress, healthy lifestyle, sleep rhythm and sense of control over one's own body. If we want to treat pain properly, we need to look beyond the knee.


What are the symptoms in kneecap pain?

Patellofemoral complaints consist of pain around the kneecap. The pain is sometimes difficult to pinpoint and may vary in location. The pain may radiate a bit and in occasionally even be felt in the hollow of the knee. Patellofemoral complaints are frequently bilateral.

No swelling is usually present. Bending and extending the knee is fine as long as there is no force on the leg. Around 30 degrees of flexion, the knee may lock up. After a little shaking, bending and stretching, that feeling, sometimes with a loud click, is gone again. By itself, this does not cause any harm. Often this is because the kneecap does not track properly through the trochlea for a while.

Because the tracking of the kneecap over the upper leg is not going well, it can crack (crepitations) and hurt when walking, climbing stairs and sitting and standing up. People also complain when sitting for long periods of time (theater/cinema phenomenon), driving a car, going down hills/mountains. Movements with a lot of flexion in the knee such as squats, squats, but also cycling with high resistance (hills, headwind and/or heavy acceleration) can provoke complaints.

How can you examine kneecap complaints?

The complaints have a fairly clear pattern of symptoms and can therefore be reasonably to well assessed by a general practitioner or physical therapist. Diagnosis is done through an interview and physical examination. Additional examination such as an X-ray or MRI is not necessary. Patellofemoral complaints usually respond with difficulty to treatment because the causes are often diverse. This quickly leads to anxiety and uncertainty about the diagnosis, which is why in practice an MRI is often made anyway. An MRI of the patella usually shows no abnormalities, except possibly a high position of the patella, cartilage damage or degenerative abnormalities.

During the interview, symptoms, possible causes and the course of the complaints are identified. During the physical examination we will check if there are no other causes for the knee complaints and which factors influence the maintenance of the patellofemoral complaints. Based on this, an adequate treatment plan can be drawn up.

Patellofemoral complaints are usually difficult to treat and frequently clients are referred to the orthopedic surgeon. The orthopedist repeats the history and physical examination. Additionally, an X-ray is usually done and an MRI only in extreme cases. In general, these complaints cannot be treated surgically. The orthopedic surgeon has an extensive referral network and can refer clients specifically.

How can you treat kneecap pain?

Since the cause of patellofemoral pain is multifactorial, there are several treatment options. It is important to note that the kneecap is a link in a total functional movement chain. Therefore, treatment can focus on the back, hip, ankle, foot and, of course, the knee itself. The exercises are aimed at optimizing the alignment of the knee which reduces the pressure on the kneecap. In addition, treatment may include pain education and explanation of the (complex) mechanism of action of pain.

The symptoms are usually present for a long time before treatment is started. Recovery therefore takes more time. The course also often varies with periods of more and less pain. An often heard reason is insufficient matching of the load to the capacity of the knee.

There is no consensus from science on the most efficient treatment. Each rehabilitation will require individual determination of the best approach.

Treatment options based on different categories of exercises:

  • Load management
  • Core stability/trunk stability
  • Stability of the pelvis
  • Training large and small buttock muscles
  • Stability Training
  • Stretching exercises of hamstrings a tendon plate outer thigh
  • Strength training upper leg muscles
  • Coordination Vastus Medialis Oblique (VMO).
  • Mobilizing patella
  • Knee tape
  • Ankle stability, mobility and possibly orthotics

Kneecap complaints based on overuse.

If there is overuse of the patellofemoral joint, it is necessary to reduce the load on the knee. Overuse from sports is common. Periods of longer, more intense or increased exercise are causes of symptoms. The body needs time to get used to certain loads. A simple rule is that the scope (how many training hours and intensity) can go up 10 percent per week followed by an adaptation week where training hours and intensity remain the same. In cases of symptoms, it is important to avoid peak loading on the patellofemoral joint. Adjust the duration of the load or take a few days of rest/recovery training. If this has insufficient effect, a relative rest period of 2-4 weeks is wise.

In addition to peak loading, it is also necessary to be careful with duration loading. Long bike rides or hikes through the hills, sitting with the leg bent for long periods of time can provoke the symptoms.

Kneecap complaints based on disrupted alignment.

In the study, we described that several factors in the movement chain affect the patellofemoral joint. Consider posture, joint mobility, muscle strength and coordination of movement. The physical therapist formulates a treatment based on his examination. Think of muscle strength training, coordination training, mobilizing exercises, stretching exercises etc.

Assistive devices such as tape or braces can be used. This can quickly give (temporary) reduction of complaints so that recovery exercises can be performed without provocation of the complaints. In the longer term and maintaining results, treatment based on exercise therapy and load management seems to be the most successful.

Kneecap complaints with low back involvement.

Low back involvement in patellofemoral complaints should be treated in a targeted manner. The physical therapist assesses the mobility and stability of the back. In addition, the low back is assessed in relation to daily use and sports.

Treatment will include postural advice, mobilizations, exercises and training of the back muscles. A manual therapist may be consulted if necessary.

Patella complaints with involvement of sensitization.

Due to prolonged pain symptoms (> 3 months), the pain system can become overstimulated. The treatment is aimed at bringing this system back to rest. The content of the treatment includes pain management and explaining the complaints. Here the assumption among clients is that the pain is a signal that something is broken or about to be broken. The cracking sound is usually related to the wearing down of cartilage. The snapping or popping sounds the kneecap makes must also be wrong is the thought. A knee specialist can give you detailed information about this. In short, the pain is not a sign that something is breaking down. The cartilage does not wear down harder when you hear the cracking sound and the snap does not hurt. Still, clients worry. Will they still be all right? They start moving differently and the worry, read stress, increases the pain. An experienced knee specialist is important to consult in this one. Much of the treatment focuses on pain management, but the load-bearing capacity of the knee and mobility chain must also be built up.

Kneecap complaints based on cartilage damage.

Cartilage damage occurs to varying degrees. When there is minor damage behind the kneecap, we speak of retropatellar chondropathy. When the cartilage surface behind the patella is damaged to a large extent, we speak of osteoarthritis. For more information on this, see the section osteoarthritis.

Treatment consists of several components. Preventing peak loads (such as jumping and long squats).Regular light-intensity exercise to keep the patellofemoral joint well "lubricated"; supple. Regular cycling helps with this.Keeping the patella mobile. A physical therapist can help keep the patellofemoral system moving properly. For example, by mobilizing the kneecap so that it can make all desired movements.Training the thigh muscles. This improves the stability and control of the patellofemoral system. Optimizing the chain of motion. In addition to the knee, disruptions elsewhere in the movement chain are considered.