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Hamstring pain: how does a hamstring injury happen?
For footballers, it is a familiar story: sudden sharp, tight-feeling pain in the back of the thigh. Hamstring injuries have been among the most common injuries within (professional) football for years. Often, hamstring injuries are seen as one and the same problem. And that is precisely where things can go wrong.
Not every hamstring injury is the same and this directly affects the recovery process. In previous blogs, we have explained that the location of the injury is of great importance. An injury limited to the muscle fibres usually has a more favourable course. However, when the actual injury is more towards the tendon or central aponeurosis, recovery is arguably slower and the likelihood of recurrent symptoms is higher.
New research from 2025 adds an important layer. It shows that even individual anatomical variation plays a role, especially in the shape and structure of the hamstrings. This variation strongly influences which tissue comes under load and how well an injury can recover.
This insight helps explain why two players with similar hamstring injuries can nevertheless go through a completely different recovery process. Rehabilitation of hamstring injuries increasingly requires customisation based on an understanding of both tissue type, location and anatomy.
Anatomy of the hamstring
The hamstring consists of three muscles that all spring from the ischial tubercle (tuber ischiadicum): the semimembranosus, semitendinosus and the long head of the biceps femoris. At the level of this attachment, they share a common tendon structure.
What makes this region special is that this joint tendon continues into the muscle belly via connective tissue, particularly in the long head of the biceps femoris. On imaging, this is visible as a characteristic T-shaped pattern, where tendon, aponeurotic connective tissue and muscle fibres come together. This structure is known as the T-junction in the English-language literature.
Anatomically, this area is not a simple transition, but a complex network of different tissue types. This very combination makes the hamstring particularly vulnerable to injury in some cases, especially under high speed and sprinting loads, as is common in football.
A longer or shorter central aponeurosis of the hamstring
Not everyone has the same hamstring anatomy. Research shows that there are roughly two anatomical variants. In some athletes, the central aponeurosis, the vertical part of the T-junction, extends deep into the muscle belly of the long head of the biceps femoris. In these cases, the aponeurosis comprises more than 30% of the total muscle length. This is referred to as a long T-junction.
In others, this aponeurosis remains more restricted to more proximal to the muscle. We call this a short T-junction. This anatomical variation appears to have a major impact on both the course of an injury in this area and the risk of and new hamstring injury.
Importantly, this is not just about injury susceptibility. But when the central aponeurosis becomes involved, recovery proceeds biologically differently from a pure muscle tear. Muscle fibres have a relatively good recovery ability and recover with functionally similar tissue. In contrast, connective tissue structures such as an aponeurosis recover with scar tissue that is less elastic and less load-bearing than the original tendon-like tissue.
Figures speak for themselves
In a study of 32 professional football players with a first hamstring injury, confirmed via MRI, recovery was closely monitored. The results showed a clear difference between the two anatomical variants.
For players with a long T-junction the average recovery time was 42.6 days, 37.5% of this group re-injured within six months.
Players with a short T-junction recovered on average in 28.9 days. Within six months, 6.3% of these players were re-injured.
These differences are very important and explain why a standard timeline in hamstring rehabilitation often falls short.
Why this big difference in recovery time for a hamstring injury
To understand this, research was also conducted, examining the anatomy of 10 bodies in detail. Here, it became clear that this T-junction anatomy can be really different between people. Not only in how deep the connective tissue runs through, but also in thickness and density of that tissue.
This largely explains the difference in recovery. Because it is not just about the size of the crack, but precisely about what is torn. With a long T-junction, you are more likely to have injury in or near that aponeurotic tissue. And therein lies the problem: damage to this central aponeurosis actually heals differently from muscle fibre tears. Slower, with less functional scar tissue, and more likely to re-injure under stress.
Ultrasound for hamstring injuries
Ultrasound can be a valuable additional tool in hamstring injuries, when performed by an experienced therapist. The main advantage of ultrasound is that it dynamic understanding offers in the tissue of interest. It enables not only imaging of the structures involved, but also monitoring changes in tissue quality and assessing how the area responds to movement and strain. Especially in muscle-tendon transitions and aponeurotic tissue, ultrasound can help provide direction to the clinical picture, complementary to physical examination.
What does this mean for rehabilitation for hamstring injuries
For rehabilitation, this knowledge means a shift in emphasis from caution to greater understanding. Particularly in athletes with a long T-junction, the recovery mechanism may be different and the tissue involved remains more vulnerable under high stress. This is not to say that there is a slower build-up schedule, but rather to have sharper decision moments towards return-to-play. Return to sport is only justified when strength, control and load capacity are fully restored, even at high speeds and complex movements, without residual pain or movement restrictions. It is precisely at this point that the risk of renewed overloading of the central aponeurosis is reduced.
The main conclusion is that not every hamstring injury is the same, even when the diagnosis appears identical on paper. Two players with what appears to be the same hamstring rupture can biologically recover from two different problems, depending on the tissues involved and the anatomical structure of the T-junction. Anatomical variation thus provides an important explanation for differences in recovery time and the likelihood of re-injury. For athletes with recurrent hamstring injuries, this underscores the importance of an approach based on understanding anatomy, tissue behaviour and load capacity rather than standard timelines or a generalist approach.
