SymptomsComplaints
Injuries (trauma), repetitive microtraumas, instability in the knee joint, muscular imbalance in the knee and inflammation of the synovial membrane (synovitis) cause swelling and thickening of the plica. (fold of the mucous membrane). Repeated entrapments with inflammation and fibrotic remodelling result in a self-sustaining process associated with recurrent pain, joint effusion, movement restrictions, joint snapping and joint blockage.
In the case of shelf syndrome, the pain is localized on the inside and is load-dependent. Sometimes there are blockages between the inner edge of the kneecap and the lower part of the femur (femoral condyle) during the stretching movement. Frequently a rubbing or snapping motion is felt at the inner patellar margin.
The increasingly connective tissue remodeled (fibrosed) plica mediopatellaris is often palpated as a painful strand. Sometimes there is a cracking of the joint in a certain position during joint flexion. Depending on how severely the shelf syndrome has already progressed, a distinction is also made between the complaints that are triggered by it.
At the beginning of the disease, there is usually load-dependent pain in the area of the knee. Movements often trigger complaints, which are above all very stressful for the knee and muscles. Movements such as climbing stairs, cycling or jogging should be mentioned here.Swimming, on the other hand, is considered a gentle way of moving.
In addition to sports activities, prolonged standing and uneven loading of the knee joint are described as aggravating symptoms. At the onset of the disease, these movements must be performed for a long time before the patient complains of symptoms. These are mostly pains that originate inside the knee.
The pain is often described as pulling or biting. It can also wander and can then be localized from inside the knee further upwards. The pain is often triggered during the actual movement, lasts as long as the movement is performed and then decreases as soon as the knee returns to a resting position.
The pain can thus be provoked by movement, but only when the strain is intense is it usually triggered at the beginning of the disease. As the disease progresses and the degree of inflammation increases, an influx of inflammatory fluid into the knee joint may occur. This can then lead to swelling in the knee, which in turn leads to a reduction in space in the joint.
The tightness in turn leads to tension pains, which the patient can experience in addition to the symptoms of shelf syndrome. The swelling in the knee joint can also mean that the knee can no longer be bent or stretched in the usual way, the kneecap can move away from the knee in the event of severe swelling, lifted off by the effusion, and thus become clearly palpable. Sometimes there may also be signs of a so-called “dancing patella”.
This is a kneecap lifted off by fluid, which seems to float above the knee joint and can be pushed to the side with slight springiness by applying slight pressure. If a shelf syndrome persists for a long time and has not been treated, the inflammatory reactions of the body intensify. While initially only heavy loads led to the complaints in the knee, now even relatively light movements can cause the complaints.
The reason for this is that the inflammation in the knee joint can no longer be cured and reduced by resting, a certain residual inflammation always remains in the knee, even if no heavy load is being placed on the knee at the time. The symptoms also increase in intensity. For example, the pain occurring in the knee joint is described as being much more biting and pulling than in an incipient shelf syndrome.
Effusions can also occur earlier and build up more quickly. A redness can be seen rather rarely in a pronounced shelf syndrome. In addition to the pain and the impairment of movement, those affected also repeatedly describe an audible cracking sound that occurs when the stretched leg is brought into a bent position or vice versa.
The cause is probably a sudden, jerky drop of the condyles in the knee joint. This is also a sign of incipient instability in the knee joint. Corresponding pain caused by an incipient but also advanced shelf syndrome also causes patients to adopt a relieving posture during normal movements in the knee joint in order to reduce the corresponding pain.
This relieving posture also inevitably leads to incorrect loading of the knee joint. The knee is no longer loaded in the usual way. Acutely, incorrect loading leads to further pain, which the patient additionally perceives.
In the long run, however, such incorrect loads lead to arthroses of the upper and lower leg, but also of the pelvis. As a rule, however, therapy is initiated when the shelf syndrome progresses. If a shelf syndrome is very pronounced or has been developing for a long time, pain at rest can also occur without any corresponding movement being exercised.
At this point at the latest, all patients should consult their physician, because failure to treat them would lead to an increasing loss of movement. The trapped plica can usually be mobilized again with appropriate movement, which then reduces the pain peak accordingly. Sometimes, however, it can also happen that this entrapment cannot be released by movement and remains.
At rest or during movement, this leads to severe to very severe pain. Patients usually try to find the most bearable position for themselves by making the slightest movement in the knee joint, and are usually plagued by severe pain. Even with this relatively rare course of a shelf syndrome, rapid action is required to prevent irreparable damage to the knee joint.
