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Anterior Knee Pain: causes and treatment

Knee pain can be caused by various factors, therefore, it is important to identify them and avoid certain activities that prolong the pain and injure it even more.

Fig. 1 Extensor mechanism

In the daily practice of medicine, it is very common to consult a patient who has a pain in the knee in the anterior region, which in the vast majority of people appears without prior trauma, but which, in some cases, can appear after a mild trauma or a surgery.

This pathology is the most frequent cause of consultation for knee pain without previous trauma, and it may also be the most frequent cause of poorly indicated knee surgeries. For these reasons, it is important to explain the causes in detail and for patients to consult with an expert orthopedist.

To explain this, it is necessary to answer the following questions:

What is the anatomy of the knee and what is the extensor mechanism like in the anterior part of the knee?

The knee is a joint between the distal femur (condyles) and the tibial plateaus.

It is a very unstable joint from a bone point of view. The stability of the knee is given by the menisci, ligaments and muscles that act synergistically to keep the knee in a good position without dislocating. The Loss of this balance generates serious mechanical problems to the joint.

The muscular balance is established by the sartoriom quadriceps crural in the anterior part with its four components: the vastus intermedius, vastus lateralis, vastus medialis and rectus femoris; the hamstring muscles (semimambranosus, semitensinosus, biceps femoris in the posterior part; the adductors and gracilis muscles in the medial part; the tensor fascia lata and the iliotibial band in the lateral part. In addition, the medial and lateral gastrocnemius are stabilizers , and the popliteus.

The knee extensor mechanism (Fig. 1) is made up of the quadriceps, patella, and patellar tendon. The patella is a sesamoid bone with two main facets, medial and lateral, the latter having the greatest surface area. It is covered by a very thick articular cartilage to withstand the high compression loads generated by the extensor mechanism. This cartilage is up to 5mm thick, being the thickest of the articular cartilages in the body.

The functions of the kneecap are:

  • Improve the efficiency of the quadriceps by increasing the lever arm of the extensor mechanism
  • Centralize the divergent forces of the quadriceps
  • Resist compressive forces with minimal friction
  • Protect intra-articular structures
  • Knee cosmetics

The quadriceps tendon inserts into the superior pole of the patella and is reinforced by the medial and lateral retinaculum, expands over the patella and then all fibers converge to form the strong patellar tendon to insert into the anterior tibial tubercle.

How does the extensor mechanism in the front of the knee normally work?

The biomechanics of the patellofemoral joint is based on the synergistic function of the patella and all those static and dynamic stabilizers centering it to allow a harmonious and smooth glide on the femoral trochlea. The knee has constant loads at rest given by the muscles and tendons. The quadriceps, being a muscle, generates a force (vector) of downward attraction.

The result of these forces is a backward vector that causes the patella to be in intimate contact against the femur in a harmonious sliding with the minimum coefficient of friction (Fig. 2).

Why does my knee hurt due to lack of flexibility?

When there are retractions of the quadriceps muscle, a higher traction force is generated, causing an increase in the quadriceps vector, which in turn increases the resultant backwards and therefore the pressure exerted by the kneecap on the femur. Yes, there are also interactions of the hamstring muscles (knee flexors) that are at the back of the thigh and insert into the tibia backwards, causing the tension in the patellar tendon to increase and the resulting vector to increase as well.

Furthermore, this traction of the tendons generates the Tendonitis of the goose’s foot. If there are retractions in both muscle groups, as is most common, this resulting vector will increase exponentially (Fig. 2 red lines). Thus, pain appears due to increased pressure and if this pressure persiststhe exposed cartilage begins to soften and then crack, appearing trachydos, friction, chondromalacia and late Patellofemoral osteoarthritis.

What activities increase this Anterior Knee Pain?

It is important to know that as the knee changes position from extension to flexion, the contact areas of the patella with the condyles vary and likewise the contact pressures become increasingly greater as the knee flexes more.

Initially in extension the patella is partially “subluxated” laterally and at the beginning of flexion it becomes centralized until at 20-30° of flexion it comes to direct and central contact with the femoral trochlea and continues this way for the rest of the flexion. knee. In flexions greater than 90°, this patellofemoral pressure increases.

All activities that involve forced flexion of the knee such as kneeling, squatting or sitting for a long time will increase this pressure and therefore the pain becomes greater in these activities in people with Disbalance due to lack of flexibility. Other activities such as going up and down stairs increase patellofemoral pressure because it involves forced contraction of the quadriceps, increasing the resulting force backwards (red vector) and people with Anterior Knee Pain will be affected by these activities.

Fig. 2 Tensile forces at the knee

What is the treatment for Anterior Knee Pain due to Muscle Imbalance?

When the diagnosis of Muscular Imbalance is made, Tendonitis For goose bumps or secondary patellar chondromalacia, it is essential to do physiotherapy aimed at improving muscle flexibility through stretching. By improving flexibility, the increased red loads will be changed to normal loads, as seen in black (Fig. 2).

Activities that exacerbate pain such as those mentioned above, such as excessive climbing and descending stairs, squatting, squatting or kneeling, should be avoided.

In most cases, they are patients who begin doing sports activities in gyms and after a few weeks of exercise they manifest pain. A specialized medical evaluation is very important to rule out other types of injuries.

What exercises can I do?

The patient you must stretch and have complete flexibility to eradicate the symptoms. In the gym, you should tell your instructor or trainer that they should emphasize your flexibility. You should avoid climbing exercises, spinning, strengthening exercises that involve doing the entire range of motion of the knee.

It is essential that the exercises for the lower limbs must be isometric. Performing activities such as riding a bicycle with the seat high so that the patient can reach the pedals, elliptical, non-impact treadmill and many stretches such as yoga and Pilates classes, are very beneficial for this type of pathology since they focus on apply effort just stretch the muscles.