Cruciate ligament rupture
What is a torn knee ligament?
The knee joint is the largest joint in the human body and has a complex ligamentous apparatus. The four most important ligament structures are the anterior and posterior cruciate ligaments as well as themedial and lateral collateral ligaments. If a knee ligament is torn, one or more of these ligaments are injured. Other structures in the knee may also be injured (such as a meniscus).
What is the function of the cruciate ligaments?
The cruciate ligaments are one of the most important central stabilisers of the knee joint and connect the thigh bone to the lower leg bone. The knee has an anterior and a posterior cruciate ligament that cross in the centre of the knee joint.
How does a cruciate ligament rupture occur?
A cruciate ligament tears as a result of an accident, e.g. when skiing or playing football. In the case of the anterior cruciate ligament, this is caused by a bending and twisting movement of the knee joint with the lower leg in a fixed position. The anterior cruciate ligament is a bundle of fibres about 2 to 3 cm long and as thick as a little finger. In most cases (approx. 90 per cent), the anterior cruciate ligament tears (ACL rupture).
What are the symptoms of a cruciate ligament rupture?
Tearing of the anterior cruciate ligament is usually associated with an audible pop, followed by brief pain and joint effusion with resulting restriction of movement and weight-bearing. The nerve fibres and blood vessels running through the cruciate ligament are responsible for this. When the cruciate ligament tears, the nerve fibres trigger the pain and the torn blood vessels cause bleeding into the joint. The affected person usually notices the instability in the knee joint immediately afterwards or after the acute pain symptoms or knee swelling have subsided. The knee joint bends uncontrollably, which is also known as "giving way".
What consequences can a cruciate ligament rupture have?
The rupture of the anterior cruciate ligament results in an abnormally increased range of motion of the knee joint. In order to slow down this increased mobility, the existing structures in the knee joint, such as the meniscus and cartilage, are subjected to significantly more stress. In the long term, this additional strain can lead to consequential damage such as a torn meniscus and cartilage wear (knee osteoarthritis).
How is a torn ligament examined and diagnosed?
During the clinical examination, the instability of the knee joint is checked by testing how far the lower leg bone can be moved in relation to the thigh bone. The knee joint is also examined to check whether additional pain can be triggered.
An MRI (magnetic resonance imaging) provides further information about the cruciate ligament rupture and accompanying injuries such as collateral ligament or meniscus tears and cartilage injuries.
How is a torn ligament treated and treated?
A torn cruciate ligament can be treated conservatively or surgically. Which method is chosen depends on the age and needs of the patient (e.g. sporting and professional requirements) as well as the type and localisation of the cruciate ligament rupture and its accompanying injuries (e.g. additional meniscus tear). Possible previous damage to the knee joint (cartilage damage, knee osteoarthritis) also plays a role.
Conservative treatment methods
If only the cruciate ligament is torn and other concomitant injuries (meniscus tear) can be ruled out and the level of sporting and professional activity is very low, the cruciate ligament tear can be treated conservatively. Physiotherapy is used to strengthen the muscles and thus stabilise the knee joint.
If, despite this therapy, there is still uncertainty (instability) and the patient can no longer cope with everyday life, surgical repair of the knee joint should be considered.
Surgical treatment methods
The more active and the younger a person is, the sooner the torn cruciate ligament should be treated surgically in order to counteract possible consequential damage(meniscus tear, knee arthrosis). Today, there are various minimally invasive methods(arthroscopy) for repairing a torn cruciate ligament. We differentiate between cruciate ligament-preserving surgery and cruciate ligament replacement.
Cruciate ligament preserving surgery
Cruciate ligament-preserving surgery can be performed if the cruciate ligament is torn directly or close to the femur. In these cases, the torn cruciate ligament can be splinted with a strong suture and reattached to its origin (internal brace, see image). This stabilises the patient's own cruciate ligament. In addition, the torn cruciate ligament is sutured (cruciate ligament suture) in order to promote the self-healing of the patient's own cruciate ligament.
Concomitant injuries (e.g. torn meniscus, cartilage damage) can be treated during the same operation. This suture and the splinting of the torn cruciate ligament are performed using minimally invasivearthroscopy and thus support the self-healing of the patient's own torn cruciate ligament. This innovative surgical technique results in a stable construct, which enables immediate early functional, aggressive follow-up treatment with a temporary knee brace.
Cruciate ligament-preserving surgery should be performed within three weeks of the accident, as the torn cruciate ligament then shortens too much.
Cruciate ligament replacement surgery (cruciate ligament plastic surgery)
Reconstruction of the torn anterior cruciate ligament (ACL rupture)
In cruciate ligament replacement, the non-functional, torn cruciate ligament is removed and in most cases replaced by an autologous tendon. In exceptional cases, an artificial cruciate ligament can also be used.
The operation is performed either within 24 hours of the accident or two to four weeks after the injury. The knee swelling and haematoma should have healed. In addition, the mobility of the knee joint should have improved again.
Correctly performing cruciate ligament replacement surgery is technically demanding. We use the so-called bone-tendon-bone technique, which is a common procedure and means that the new, autologous cruciate ligament graft consists of a bone block, a tendon part and another bone block. This involves taking a part of the patellar tendon on the inside with the corresponding bone block from the tibial plateau and a bone flake from the kneecap. These bone blocks then heal in the drilled-out attachment points of the former cruciate ligament. The bone blocks take around six weeks to grow in. To ensure early stability before ingrowth, the bone blocks are secured with screws (some of which can be dissolved), sutures and special metal plates (clip anchors).
The majority of the operation is performed arthroscopically (joint endoscopy, minimally invasive). An additional incision must be made along the patellar tendon only to remove the new cruciate ligament graft. The knee joint can then also be opened via this incision (so-called "mini open"). Possible concomitant injuries (e.g. meniscus tear, cartilage damage) are also treated in the same session.
This technique enables immediate early functional, aggressive follow-up treatment. It is important to have good physiotherapy that accompanies you and rebuilds you for a specific goal. In addition, regular follow-up checks are carried out by the surgeon. Light sporting activities (e.g. cycling) are usually possible again after three months. Contact sports or sports with a lot of stop-and-go are recommended after six months at the earliest, depending on the respective muscle status.
Reconstruction of the torn posterior cruciate ligament (ACL rupture)
The surgical technique for the reconstruction of the less frequently torn posterior cruciate ligament is similar to that of the more frequently torn anterior cruciate ligament and as described above. The posterior cruciate ligament is longer, thicker and more stable than the anterior cruciate ligament and prevents the lower leg from falling backwards in relation to the thigh. The posterior cruciate ligament tears when a high force is applied directly to the bent knee.
The surgical effort involved is significantly greater and more complicated. As the posterior cruciate ligament is longer than the anterior cruciate ligament, the body's own tendons on the inside of the knee (semitendinosus and gracilis tendon) or the quadriceps tendon are used instead of the patient's own patellar tendon as a replacement. The new graft must be longer and thicker. This is inserted arthroscopically at the original location of the posterior cruciate ligament after appropriate overdrilling of the femur and tibia and fixed with screws (dissolvable) and clip anchors.
In contrast to anterior cruciate ligament reconstruction, follow-up treatment is very cautious. The operated knee must not be loaded or actively flexed for six weeks. In addition, the patient must wear a special knee splint (PTS splint: posterior tibial support splint) for six weeks. This PTS splint contains a pad that pushes the lower leg forwards in comparison to the thigh. From the sixth week onwards, a special posterior cruciate ligament splint is applied during the day for a further six weeks.
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PD Dr Andreas L. Oberholzer
FMH specialist in orthopaedics and trauma surgery. Areas of specialisation: Knee, hip and foot surgery.