Beat Kneecap Pain

Kneecap pain is a common condition. It is reported that up to 30% of sports enthusiasts or young people may experience frontal knee pain occasionally. It has been shown that this type of pain is associated with abnormal patellar-femoral joint tracking, stress on the kneecap and femoral trochlea, or misalignment of the lower limbs. Here to teach you all about frontal knee pain is Beijing United Family Hospital (BJU) Chair of the Department of Orthopedics, Dr. Jike Lu. 

First of all, let us talk about the patella, more commonly known as the kneecap. It plays an important role in the knee joint. The upper end of the patella is connected to the quadriceps and the lower end is connected to the patellar ligament.

Photo source: prokneepainrelief.com/muscles-of-the-knee/

The patellofemoral joint is the joint formed by the patella and femur (thigh bone). When you bend your knee, your patella slides through a groove in your femur called the femoral trochlea. If the patella does not slide properly on top of the femoral trochlea as the knee bends and straightens, it will get worn down. Abnormal position or pressure can cause pain and wear, which can eventually lead to traumatic or degenerative arthritis. Thus, it is important to keep the patella tracking normally.

The quadriceps muscle is attached to the top of the patella, and the patellar ligament is attached to the bottom. If the quadriceps muscles become weak, the patella may not be able to slide properly. One of the quadriceps muscles in particular, the vastus medialis oblique, is the most vulnerable muscle in our body. If it becomes wasted, the patella will get pulled by other muscles to the outside of the knee joint. There are other structures in the knee that are also important for normal patellar tracking. If these structures become unbalanced, the kneecap may not be able to move normally, causing injury.
 

Now, let us talk about the biomechanics of the patellofemoral joint. These are very important, especially in people with pain in the front of the knee. When people are standing or walking, the loading force of the patellofemoral joint is equal to that of the body weight. When climbing stairs, it reaches three to four times the body weight. When squatting, it can reach up to seven to eight times the body weight.

When the knee is straight, the patella basically does not come into contact with the tip of the femur. Therefore, the patella only gets worn down when the knee is bent. When the knee is bent to about 30 degrees, the patella and the femur come in contact and pressure is generated. When the knee is bent to 60 degrees, the patella and the femur lie in close proximity to each other and this high-stress condition can cause pain. In general, if you do a squat and have your knees bent at 90 degrees or more, there can be a lot of stress on your patella.

Furthermore, there are also some congenital factors that cause knee pain, such as abnormal position of the patella, having a small patella, or having a relatively shallow groove in your femur for your patella to slide through. People with wide hips or narrow knees may also have an unstable knee joint.

There is a common misunderstanding that activities like, running, going up and down stairs, and squatting are not good for the knee. In reality, it depends on the specific situation. If patients already have osteoarthritis or osteochondromalacia of the patellofemoral joint or pain due to unbalanced static and dynamic forces around the patella, then running or going up and down stairs will further damage the knee joint cartilage. However, healthy people are allowed and encouraged to run and squat.

During periods of chronic illness, pregnancy, and prolonged immobilization, people don't walk around and use their legs as much. This results in vastus medialis oblique wasting and gluteus muscle contraction. This leads to imbalances in the knee joint, which can cause pain. Rehabilitation, strengthening, and stretching of these muscles are necessary. A physiotherapist will help patients to train these muscles and restore the dynamic balance of the patella to regain its normal tracking.

It's not just long-term or chronic injuries that affect the knee. As we all know, some young people may experience dislocation of the patella when doing sports. This happens when the patella comes out of its normal spot within the femoral trochlea. When the patella is dislocated, the medial patellofemoral ligament may be torn. If a patient has recurrent dislocation of the patella, their medial patellofemoral ligament may need to be reconstructed or repaired.

If you are a young or middle-aged person experiencing pain in the front of your knee, I would like to recommend seeing an orthopedic surgeon specialized in sports medicine as soon as possible. The doctor will give correct and scientific advice to help you to do exercises in your daily life, preventing further damage of the cartilage, which may eventually lead to osteoarthritis.

Dr. Lu is the Chair of the Department of Orthopedics, Sports Medicine, and Spine Surgery at Beijing United Family Hospital. To schedule an appointment with him, call the BJU Service Center at 4008-919191.

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