Profile:
Dr. Lam graduated from the University of Toronto in 1998 with a Bachelors’ of Physical and Health Education, and then went onto study at the Canadian Memorial Chiropractic College, graduating in 2003. Since he has been in private practice and in 2007 he started FITS a high performance training centre and sports medicine clinic that features a movement based approach to prevent injuries, manage existing injuries and enhance performance. FITS is a dream come true for Dr. Lam, whose passion is to build a world leading company that Builds Better Athletes.

Written by: Dr. Thomas Lam on April 25, 2012.

Quick Summary:

The interaction between temporal factors (the amount of exposure) and neuromuscular control will determine the load characteristics to the knee – this is the biggest determinant to the development of jumper’s knee. Main movement dysfunctions that occur with poor neuromuscular control include: 1) poor knee control (dynamic valgus), 2) poor trunk and pelvis control, and 3) poor ankle and foot control. Addressing motor control issues is our best strategy to prevent and manage patellar tendinopathies.

What Factors contribute to the development of Jumpers Knee?

The key factor that causes patellar tendinopathies are repetitive stress / load characteristics placed on the patellar or quadriceps tendon. Note there are other factors, namely hormonal contributions and neovascular contributions that are beyond the scope of this article that also contribute. As a result we’ll focus on the mechanical model to explain patellar tendinopathy.

The factors that effect patellar loads are primarily related to an athlete’s technique / control[8] of their body during jumping, hopping, landing, running and changing direction during sport and the amount of exposure (temporal factors) to those loads. Note the amount of exposure and the exact biomechanical loads applied to the tendon that cause a tendinopathy is not clear. Below is a diagram that illustrates the interaction between key factors that contribute to the development of jumpers knee, primarily focusing on the stress / load characteristics that are applied to the patellar tendon:

• temporal factors,
• biomechanical factors and neuromuscular control,
• Anthropometric combined with biochemical, nutrition and hydration factors
• intrinsic factors

It is important to understand the following points related to the diagram:

• Loads can be either good or bad. An appropriate overload load will lead to a positive adaptation, while an overloaded tissue will begin to breakdown causing the onset of patellar tendinopathy.
• Reversibility above degenerative tendinopathy. Based on modifying stress / load characteristics to the patellar tendon studies have shown that the process is reversible, but NOT once degenerative tendinopathy has occurred.
• It is the interaction between Neuromuscular Control combined with Temporal Factors that primarily determines the stress / load characteristics to the patellar tendon.

Understanding Temporal Factors

This concept refers to the amount of time exposure to patellar loads. Key considerations include the following major categories:

• Game Exposure
• Practice Exposure
• Tournament Exposure

For each type of exposure we’re interested in the amount of time per session / per week / per month and the density of the exposure compared to rest for a given period of time.

“Exposure to Rest Ratio”

High density exposure can exceed tissue adaptation or recovery leading to the beginnings of patellar tendinopathy. A delicate balance between adaptation and breakdown exists which is determined primarily by neuromuscular control. To illustrate this important concept lets’ compare two athletes. Athlete A and B play on the same rep team and they are exposed to identical game exposure, practice exposure, and tournament exposure. Athlete B develops a tendinopathy while Athlete B does not? Why is this the case?

The most common explanation relates to neuromuscular control or movement quality. To illustrate this point let’s take a look at the following video, assuming that athlete B represents a movement pattern seen in the video.

Athlete B: Demonstrates significant dynamic valgus with poor trunk and pelvis control. This leads to increased patellar load.

In comparison here is an idea pattern

Athlete B (first video) is at a much greater risk per unit time of exposure due to their poor knee control – this is termed dynamic valgus. I’m sure you can observe the difference between athlete A and B. Therefore during all sport exposure Athlete A is more likely adapting, while Athlete B is breaking down. Athlete B will begin a viscous cycle that can only be stopped by addressing the causative factor … which is ….can you guess??

You guess it! MOVEMENT. The relationship between patellar loads and temporal and neuromuscular control is how patellar tendinopathies occur and how they are effectively treated. Understanding this relationship is absolutely critical in preventing and treating patellar tendinopathy. Whether an athlete moves forward or backwards in the tendonopathy continuum is directly related to the interaction between temporal factors and biomechanical factors which are based on motor control

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