Let's first explain what a tendon is. A tendon is a strong band like structure made of fibrous tissue called collagen that connects muscle to bone. It has the responsibility of transmitting force from muscle to bone. The patellar tendon connects the bottom of the knee cap (patella) to the shin bone (tibia).[ 1] The patellar tendon can develop small partial tears or complete tears from intense physical activity.[ 1] If the patellar tendon has weakened over time due to activity and improper strengthening then it can be more likely to tear. Now, what exactly is tendinopathy of this tendon? This is what most people call jumpers knee.
Patellar tendinopathy is a common overuse injury that results in a slow increase in pain at the patellar tendon over time. At first, patellar tendinopathy was thought to be inflammation (redness, swelling and pain caused by an injury) of the patellar tendon but further research has indicated that patellar tendinopathy is actually degeneration or wearing away within the tendon.[ 2] That is, the collagen fibers that make up a tendon change in structure and weaken. This happens with overuse which leads to continual micro (very small) tears of the patellar tendon. Having a gruelling training schedule and not allowing enough time of rest can disturb healing of the tendon. Therefore, degeneration of the collagen fibers occurs.[ 2] Patellar tendinopathy is diagnosed as dysfunction and pain associated with the patellar tendon and is often called "jumper's knee."[ 3] This is because activities like jumping produce a large load on the patellar tendon, which if not done properly can overload the tendon. We have a great blog on proper jumping and landing mechanics here. The pain is often just under the knee cap on the upper part of the tendon.
Furthermore, studies have shown people between the ages of 13 to 19 are more likely to get jumper's knee, especially if they are elite athletes.[ 3] Some sports in particular show higher rates of jumper's knee. For example, from a study conducted in the Netherlands, the highest rates of jumper's knee were in recreational and elite volleyball players (14.4%) and lowest rates were for soccer players (2.5%).[ 3]
How this condition occurs exactly is still being researched; but there are risk factors related to training habits and personal characteristics that can lead to jumpers knee. The more often an athlete trains per week, the longer the athlete trains for per session and the less rest per session and between sessions increases the chances of developing jumpers knee. Personal factors include: height, weight, alignment of the legs, and strength of the quadriceps (front of the thigh) and hamstrings (back of the thigh) muscles.[ 3]
This blog focused on what jumpers knee is and how to avoid it. Our next blog post will tell you what you can do if you already have jumpers knee.