The cruciate ligament
The knee joint – like all large joints – is surrounded by a capsule of solid connective tissue. Together with movable cartilage elements such as the menisci as well as the tendons and muscles, it prevents the bones in the knee joint from shifting relative to each other in an uncontrolled manner: These components stabilise the knee joint and guide its movements.
The medial and lateral collateral ligaments serve as lateral stabilisers of the knee. Both ligaments prevent the knee from giving way into a varus or valgus position, and additionally limit the rotational movements of the knee.
The anterior and posterior cruciate ligaments run inside the joint. They secure the joint from the inside and thus fulfil three mechanical functions:
- Limitation of rotational movements
- Protection against hyperextension of the knee
Prevention of the lower leg from shifting forwards (anterior cruciate ligament) or backwards (posterior cruciate ligament)
The ligaments play an important role in movement and sports: Along with stabilisation and guidance, numerous nerve fibres running through the inside of the ligaments provide information about pressure or external influences. These sensors continually report the joint position and forces involved to the muscles of the thigh and lower leg. This important exchange of information provides significant support to the muscles in performing movements as well as position and posture.
A cruciate ligament rupture therefore affects not only the mechanical stability of the joint but also the control function of the ligament. Persons who have suffered a cruciate ligament rupture often have a feeling of instability, which can be attributed to impaired joint perception (“proprioception”). As a result, athletes may no longer be able to perform movements with the necessary precision.