Anterior knee pain (anterior=located at the front part of the knee) can be caused from multiple causes for example: “jumper's knee” a term used to describe an inflammation of the patellar tendon, Patella-femoral disorders involving the joint between the patella and the end of the femur bone (hip), impingement of soft tissues and many more. These pain sensations are quite common for athletes involved in activities such as running, jumping, weight lifting etc. none the less it is also common among people working daily in prolonged standing such as guards, cashiers and hairdressers.
These pains are often characterized as of annoying and impinging charecter located under the Patella and around it. Aggravated during extension of the knee actively, climbing up the stairs, prolonged standing, during the activity and sometimes few hours after.
Knee anatomy:
Joints: the main knee joint between the femur (the hip bone) bone and the Tibia (the shin bone) is the least stable joint in the body when bringing into account its anatomical shape. In contrary to the hip joint and shoulder joint that are more of a ball and socket joint that form a “form closure” stability (stability provided by the anatomical shape of the joint). The knee joint is simply 2 bones just placed one on top of the other. This joint is more of a “force closure” joint, or joint that remains stable more due to the muscular control around it.
Another joint in the knee is the Patella-femoral joint. The patella sits in a groove at the distal part of the femur and glides in it while extending or flexing the knee.
The last joint is the tibio-fibular joint that holds the tibia and fibula bones together at the lateral part of the knee.
Muscles:
- The quadriceps muscle group is divided into 4 muscles (depending on anatomical classification) originate from the the hip itself and some from the pelvis and inserting in the top of the patella in a fan shaped insertion point (the retinaculum). From the bottom of patella originates the patellar tendon that inserts into the tibia. The purpose of this muscle is to actively extend the knee, control eccentrically the flexion of the knee and stabilize the patella.
The patella is used as a lever, crane or support point to lift the upper part of the tibia in an anterior direction allowing the the knee to extend. If it wasn't for the patella, the quadriceps would have pulled the tibia into the femur.
Under the tendon and around it there is the Hoffa fat pad and several bursaes . Bursae is a sack of synovial fluid, intended to diminish the friction between fibrotic tissues such as ligaments, tendons and bones. - the hamstrings: located at the back of the hip bone. Also divided into several muscles. This muscle actively flexes or bend the knee backwards, eccentrically control the extension of the knee, stabilize the main knee joint and rotate the knee.
- The gluteal muscles: also divided into 3 muscles that control the movement of the hip. They originate at the pelvic bone and inserts into the femur. From there, some of them insert into the illio-tibial band. A long fibrous band that originates at the pelvis and inserts into the tibia with some attachments to the patella. The ITB provides much leverage for the gluteal muscles to control the entire movement of the lower limb. Thesemuscles extend, abduct and rotate the hip and controlling it movements.
- The adductor muscles. Originate at the pubic bone and insert into the lower part of the hip and to the tibia. They Adduct the hip- bringing it to the center of the body, eccentrically control the abduction movement and stabilize the knee medially.
- The Gastrocnemius and soleus muscles: originate from the distal part of the femur and from the fibular head and insert into the achilles tendon. They provide plantar flexion movement at the ankle (tiptoe), eccentrically control the dorsi flexion at the ankle and stabilize the ankle joint. Also participate in the flexion and controlled extension of the knee.
It is very important to understand that muscular control and co-ordination of all these muscles is crucial in order to unload unnecessary pressure from the patella and generate a stable and effective movement at the knee and the entire lower limb.
Injury mechanism:
Due to overload on the patella-femoral joint or its adjacent structures an irritation process begins. Due to this overload, unbalanced forces are applied to the patella and can cause over compression of the patella against the femur or traction forces from overworked muscles or shortened tissues. This also causes the patella to move, in its groove in the patella-femoral joint, in a non stable and non functional way.
It's important to understand that even though the anterior knee pain syndrome might involve certain structures that maybe not all are affected but directly and indirectly, they are all connected in a very logical and obvious pattern in the kinetic chain.
Influencing factors:
- weakness and lack of muscular control at the gluteal muscles, abdominal muscles and pelvic floor muscles. As explained, the movement of the entire lower limb starts at the center of the body by the contraction of these muscles. If these muscles are weak or lack muscular control between them, an overload will fall on the other muscles involved with this movement. e.g the quadriceps will pull too strongly on the patella, causing a excessive traction force on the patella tendon and cause inflammation or irritation.
- weakness and lack of muscular control of the quadriceps themselves due to shortening or weakness will again cause an unbalanced traction forces on the patella.
- weakness and lack of muscular control of the hamstrings. If the hamstrings cannot control the extension movement eccentrically, there will be an excessive traction force on the patella by the quadriceps from the anterior part of the knee which will lead to excessive anterior movement of the tibia and cause impingements of soft tissues at the anterior side of the knee and lead to the same conclusion.
- Shortening of the ITB: if the lever that supports the activity of the glueteal muscles is shortened, there will be an excessive lateral traction force on the patella and tibia. This lateral traction force will have to be controlled by an overactivity of the muscles providing medial traction and again will cause over tension on the patellar structures.
- Poor proprioception: Instability or lack of control in the rest of the lower limb muscles and the pelvis. strength in these muscles is not enough. The ability of the nervous system to control the activity and timing of contraction of these muscles is just as important. There’s a vast system of sensors situated in muscles, tendons, joint capsules and even the skin that sends signals associated with stretch, tension, muscle contraction respectively to the brain. The brain processes all of these signals and develops a picture of how the movement is carried out. If this system is untrained or neglected, the movement image in the brain isn't presented properly. Therefore, over use of muscles, unbalanced contractions can occur and lead to overload on more distal structures like the knee and ankle. This system is also known as the proprioceptive system and its sensors- the propriosensors.
- Limitation in range of motion in the knee, hip, pelvis and low back: The ability of the body to generate a well co-ordinated movement depends upon the kinetic movement chain that starts at the center of the body and ends at the foot. A limitation in one of the elements of this kinetic chain will eventually over load other structures that will have to compensate for that loss by excessive range of motion on its part. A lack of range of motion can be caused by negligence, improper training and prevention or a past history of ankle and knee traumas- fractures, sprains, dislocations or age related degeneration.
- faulty ankle, knee and hip mechanics. Even though there is much debate on this matter (especially foot position- high and low arches), its only logical to assume that a joint positioned in a non symmetrical way will generate an unbalanced motion pattern and again subsequently will over load other parts of the kinetic chain.
- Trigger points- these are inner contraction points or nodules within the muscle fibers caused by overload on the muscle. These nodules stay contracted passively and limit the ability of the muscle to either generate a functional contraction or stretch (thus even limiting the range of motion even further). These trigger points might refer pain to other areas that might present symptoms. The dry needling technique (that can be read in “types of treatment” page) release those trigger points instantly, thus restoring functional contraction, muscle length and ROM.
In conclusion of this part, the main message should be that all parts of the kinetic chain should work properly and in a controlled and coordinated manner. Failing to do so, the load will have to be shared by less components and lead to their inability to function properly. The end result will be the unbalanced force applied to the patella.
Treatment:
- stop or modify your activity at its current intensity, allowing the body to regenerate and heal damaged tissues.
- Localized anti-inflammatory treatment as ultrasound, ice, connective tissue to control the inflammation in order to be able to function, but not stopping it altogether. An inflammation is an important part of the healing process.
- Muscular training of all the above mentioned muscle groups in order to achieve the equal load sharing amongst them in the kinetic chain.
- Proprioceptive, equilibrium and stability exercises.
- Stretches and manual therapy to provide a functional range of motion at the pelvis, hip, knee and ankle level.
- dry needling to release trigger points.
- Taping- kinesiotaping and athletic taping are commonly used in unloading certain structures during movement and pain control.
- The use of orthotics and insoles are sometimes used to correct a faulty joint position or train the body to work in a functional pattern.
In conclusion
anterior knee pain is a complexed issue requiring much professional attention and a broad point of view in order to evaluate the non functional parts of the kinetic chain and training them. There is a common misconception that all there needs to be done is strengthen the quadriceps muscles and all will be fine. The quadriceps are just one link in the chain. An inquiry should be taken into the training program and its intensity, range of motion, muscular control, proprioception and many other elements. Its important to remember that the longer the symptoms are present, the longer we have adapted a wrong way of training and therefore the duration of the healing process will be accordingly.
***This article mentions several methods of evaluation and treatment. These are merely guidelines. They are not an independent treatment program nor intended to replace a thorough evaluation and treatment program executed by a certified physiotherapist. Its advised to undergo such evaluation and treatment by a certified physiotherapist if such injury occurs and act upon their professional judgement call***