Does thigh length affect quadriceps strength after surgery?

There are many factors that contribute to muscle strength:

• Genetic predisposition
• Hormonal status
• Daily physical activities
• Developmental disabilities

Some factors such as physical activity and hormonal status can change in a person's life. Upper leg length or whole leg length when people are fully grown are not susceptible to change. Research shows that quadriceps strength is partly dependent on people's height and weight, among other factors. But what is the actual influence of the length of, say, the bone of the upper leg where the quadriceps has its course?

Research shows that there is a relationship between people's height and upper leg strength in people without knee problems. The taller people are, the stronger the quadriceps. We see this even in people with a leg length difference. The shorter leg is less strong in both bending and extending the knee. Unfortunately, we do not see in the study whether the volume of the muscle also played a role in this. But when we look purely at length of the upper leg, we see that people without injury with a longer upper leg are generally stronger.

The length of the upper leg i.e. the femur affects the strength on the non-operated side. Looking at individuals after anterior cruciate ligament surgery, we see that people with longer legs regain quadriceps strength relatively faster. This possibly leads us to new insights into how to deal with anatomical variation in people after knee surgery such as anterior cruciate ligament surgery. This information tells us that morphological features affect quadriceps strength. Physiotherapists and medical specialists can use this knowledge to tailor rehabilitation after surgery even more specifically to the individual and could potentially help in evaluation moments where strength differences are discussed or certain activities such as running can be resumed.

When we map quadriceps strength, we often relate it to body weight, left-right difference but also strength in relation to another important muscle group in the upper leg, namely the hamstring. Perhaps in the future we will also include femur length in the evaluation of quadriceps strength as an additional variable to consider. As with many new insights, further research is often needed to make a proper statement on this. But at Fysio Fitaal in Tilburg, we are always looking to improve our people's rehabilitation after anterior cruciate ligament surgery.