About the knee

The knee is a hinge joint that primarily has bending and stretching functions, but which also may perform small rotational movements. During a 10 km run, there might be up to 6-7000 steps, each with a load of 2-3 times our own body weight for each landing. This means a high and uniform load on the knee for each step, which is the main trigger for knee injuries caused by running.

Research has demonstrated that a 5 kg reduction of the body weight means close to 100 kg reduced load on the knee, for each step. The knee is the body joint that is subject to the highest volume of running related injuries. One of the reasons for this is weak stabilising muscles around the knee. When this is the case, the knee is subject to strong and unfavorable twists, and the muscles may quickly become overloaded, leading to soreness and overload also in the joints where tendons are fastened to the bone structure. In most such cases there are no problems inside the knee (ligament, meniscus or cartilage). Insufficient control of knee movements may also be caused by insufficient strength and stability in the muscles around the two closest joints, which are the ancle and the hip.

Pain at the front of the knee

There are many possible reasons for knee injuries that cause pain at the front of the knees. Such pain is often connected to the joint surfaces between the kneecap (patella) and the leg bone. The pain may also occur as a consequence of unfavorable pulling of the front thigh muscles (quadriceps), where the kneecap functions as a weight arm over the joint. The quadriceps muscles ends in the patellar tendon, which is fastened on the lower leg bone (Tuberositas tibia) under the kneecap. It is important that the drag on this muscle is even. If not, the kneecap may be wrongly directed, which may result in a damage on the cartilage on the backside of the kneecap.

Overload of the patellar tendon is often called Jumper’s knee (See this article: Jumper’s knee). Due to repeated jumping and running, the tendon may become sore and inflamed. In parallel, small disruptions of the fibres in the tendon may also give swelling and pain. Under the tendon, at the points where it is fastened to the kneecap and at the leg bone, there are small bursas, for the protection of the tendon against friction. If there is too much friction, the bursas (bursa prepatellaris og bursa subpatellaris) may be filled with liquid and become sore. Degenerative changes in the knee (arthrosis) may occur both on the backside of the kneecap (patella) and on the thigh- and leg knuckle. Degenerative changes may also occur when the cartilage over some time becomes worn and thin. This condition may be painful. Worn-out joint cartilage cannot be regenerated, which means that this condition is chronic. Training for stability around the knee may release the pressure on the cartilage and the meniscus, and by that relieve the pain. Pain just above the kneecap (patella) is very often originated from a large bursa (bursa prepatellaris), which may become swollen and sore due to overload.

To prevent these injuries it is recommeded to strengthen the stability of the knee. There are many exercises that can be performed for this, e.g. balance on a pillow, squats with one leg and differents stretching exercises. For a start, I recommend backwards lunges with pads, see video below:

Other good exercises to strengthen the stability of the knee are lunges in a sling, lunges with weights and the stability exercise for knee. See videos below:

Pain at the backside of the knee

As for pain at the front, there are many possible reasons for pain at the back side of the knee.

The hamstring muscles stretches down from the nates to the knee. The hamstrings are controlling the lower leg bone during the landing phase, and by insufficient strength and endurance, or by running at high speed, overload of the knee may occur. Hill running is causing even more load on the hamstrings, and consequently increases the risk of overload.

If running with the centre of gravity too much forward, due to leaning forward with the torso, the hamstring muscles will need to work hard in order to stop the fall forwards. This leads to more stress for the muscles and consequently higher load on the knee.

The hamstring muscles participates in controlling the rotation of the lower leg. If the rotation is too wide, often due to overpronation of the foot, the hamstrings may be stressed, which leads to an overload.

The lower leg muscles originates from the lower part of the thigh bone, and ensures, together with the hamstrings, that the knee is not overstretched. If running is performed with the centre of gravity too much forward, the lower leg muscles will also be overloaded.

See this pages for more about hamstrings injuries: Do you have problems with hamstrings? and Hamstrings for professionals.

Pain at the inside of the knee

knee injuriesPain at the inside of the knee is more common for women than for men.

The inside of the knee is kept stable by a side ligament (mediale collaterale ligament) and three muscles which are fastened under the knee on the inside of the lower leg bone – Pes Anserinus. The positions of the foot, knee and hip may influence the biomechanics in such a way that both tendons and different bursas are overloaded. A bursa irritation on the inside of the knee – Pes anserinus bursitt, is more common for women than for men.

Another important muscle for the stability in the knee is m. vastus medialis. This muscle may be trained effectively by the exercise backwards lunges with pads – see video above. The position of the knee is very important in this exercise. Do not allow the knee to lean inwards. This is particularly important in the movement when returning to the standing position. Concentrate on “pushing” the knee somewhat outwards. By doing so, the muscles on the inside are activated.

Pain at the outside of the knee

Pain at the outside of the knee is often a symtom of Runner’ s knee – ITBS. (See also this article: Runner’s knee). This is one of the most common running related knee injuries.

There is a wide and long tendon band – tractus iliotibialis – stretching on the outside of the thigh down to to the outside of the leg bone to a point just under the knee – the Gerdy’s. At the point where the tendon is sliding over the thigh bone knuckle, and at the fastening point for the tendon, it may become sore due to repeated movements with friction. This is what we call Runner’s knee. It is also called Iliotibial Band Friction Syndrome – ITBS.

The irritation and soreness may occur both in the tendon tissue and in the bursa – tractus iliotibialis bursa. This may be caused by:
– Insufficient flexibility of the tendon
– weak hip muscles, leading to irregular load in the knee, which further gives increased friction where the tendon is passing over the thighbone knuckle
– overpronation of the foot
– a foot with insufficient cushioning ability

The sideways plank with movement is a good exercise to prevent injuries on the outside of knee, see video below:

Knee anatomy

See detailed descriptions of the anatomy of the knee and related tendons at these pages from TeachMeAnatomy.info:

3D pictures (at teachmeanatomy.info):

See more about running injuries, preventive exercises and videos here:

Author: Hege Erichsen

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