• www.sportordination.at
  • www.sportordination.at
  • www.sportordination.at
  • www.sportordination.at
  • www.sportordination.at

Cruciate ligament

Cruciate ligament injuries


>> More detailed state-of-the-art article, please click here (.pdf 207 KB)

The knee is a rolling-sliding joint. The cruciate ligaments are the central and most important stabilisers in the knee joint. The anterior cruciate ligament prevents excessive sliding of the lower leg forwards. The posterior cruciate ligament tightens during the bending movement and prevents the lower leg from moving backwards.

Anterior cruciate ligament


Injuries of the anterior cruciate ligament are particularly common and occur in the context of external rotation movements of the leg with static lower leg and simultaneous flexion (especially common in football, but also in skiing, combat sports, in-line skating etc.) or as a result of hyperextension injuries (especially common in skiing).
Note – a cruciate ligament tear does not have to be extremely painful and is sometimes trivialised by those affected, see also PDF / courier article from Dec. 2010

Diagnosis is initially carried out clinically by means of an examination, X-ray and magnetic resonance imaging (MRI) can be used as supporting investigations.

Image: The anterior cruciate ligament (red arrow) is well depicted in the MRI
Image: The posterior cruciate ligament is also well depicted in the MRI examination (red arrow)

The main problem in the case of a cruciate ligament tear is instability. The patient feels as though the knee is giving way. As a result of the (mostly chronic) instability of the knee joint, there is overexertion of the other stabilisers of the knee joint, therefore further injuries and cartilage damage occur more often in the knee, particularly in sporty patients. For these reasons, an operation is generally recommended for top and recreational athletes.

Even though many recreational athletes (and professional athletes too) have good musculature and are able to stabilise the knee very well in the beginning, types of sport with rapid turning movements or sudden stopping (stop-and-go) cause enormous gravitational forces, which very quickly lead to meniscus and cartilage destruction in the knee joint without a stable cruciate ligament. The occurrence of high shearing forces, however, also affects people who enjoy hiking or mountain climbing (as a result of the high strain when coming downhill) and also runners who do not run solely on flat ground.

Image: Cruciate ligament tear in a typical arthroscopy view

In athletic patients, the cruciate ligament operation should take place within 14 days of the trauma, to keep the recovery time as short as possible. An additional advantage of early operation is that common injuries to a meniscus can be repaired immediately. Simultaneously occurring injuries of the collateral ligament often do not require operating on. After 10-14 days, an inflammatory reaction occurs in the knee joint (with the risk of postoperative restriction of movement = arthrofibrosis), therefore there is a waiting time of approx. 6-8 weeks after the "operation window" has passed for the next possible operation time.

The operation must be assessed in a detailed discussion and geared towards the athletic requirements, occupational physical exertion and the age of the patient. If there is the indication for surgical treatment, the cruciate ligament is replaced using an autologous tendon, as direct suturing of the cruciate ligament has not proven successful. Either two hamstring tendons (STG), the middle third of the patellar tendon (BTB), or the quadriceps tendon are used as a replacement tendon.

The choice of replacement cruciate ligament tendon is determined by factors such as level of activity, additional injuries or previous damage, degree of instability etc. and is discussed in detail with the patient.

In over 90% of patients, the cruciate ligament replacement operation can restore full function, movement and strength. However, the cruciate ligament is home to receptors that constantly send information to the brain regarding the position of the body in a space (= proprioception), and therefore also activate different muscle groups. Disappearance of these receptors alone causes a certain deterioration in fine motor skills and coordination and very often causes the knee to suddenly feel very different for the patient for months or as a patient once said to me, "...it is as though my knee no longer belongs to me...".
Depending on how consistently patients carry out coordination training (e.g. on a multifunction testing board), this feeling usually disappears within 6 – 24 months, as a result of the new formation of receptors.


  • STG (semitendinosus and gracilis transplant):

The term STG technique comes from the shortened names of the tendons used (semitendinosus and gracilis tendons).

Both these tendons are hamstring tendons that can be removed without a significant loss of strength and function for the knee joint.

The advantage of this technique is the small skin incision and the fact that the patient often suffers from less postoperative pain with the STG technique than with a BTB transplant. Most importantly, the typical pain at the extraction site of the bone blocks does not occur. Moreover, there are no problems such as patellar fracture or patellar tendon tears.

The disadvantage of the technique is that patients cannot be reintegrated into their original training programme or original exertion as quickly. The internal rotation of the lower leg may also be somewhat weakened (this primarily occurs in high-performance athletes). An additional disadvantage is that in 10-20% of cases (according to some information from literature, also in a higher number of cases), a nerve is damaged - this leads to a feeling of numbness (mostly temporary) on the medial side of the lower leg (in very, very rare cases also to burning nerve pain).

The operation begins with arthroscopy (any meniscus or cartilage damage that may be present is also treated at this time) and removal of the remnants of the ruptured cruciate ligament (if a good cruciate ligament stump is available, however, this can be left to retain the body's own receptors). The bone is then debrided in the areas of attachment of the cruciate ligament.

Contrary to the BTB transplant, an incision of only approx. 3 cm under the patella is required, via which the two hamstring tendons are taken and also through which the bone canal is drilled in the lower leg.

Then drilling is carried out for the attachment of the transplant in the femur, the STG transplant is inserted and fixed into position using a special technique. Bioresorbable screws are usually used in this method. These are screws that slowly dissolve after a few years or are re-absorbed by the body.

Image: copyright Arthrex

"All inside" technique
To ensure that the operation is as gentle as possible with less pain and a lower operation risk, I prefer the “all inside” technique for a cruciate ligament tear: during this, a tendon sutured four times (gracilis or semitendinosus) is inserted into bone recesses using smaller incisions (in contrast to the continuous bone canals used in the earlier methods, which significantly traumatise the bone and the skin on the leg and are naturally linked to significantly more pain and postoperative problems). Tissue damage is lower and the cosmetic result is significantly better as a result of the smaller incisions. I am often surprised myself by how much better the injured athletes are after an “all inside” operation in comparison to the conventional methods.

Anchoring in the “all inside” technique is carried out using endobuttons - it is therefore also the method of choice when treating cruciate ligament tears in children.

Immobilisation of the knee is only required in the case of concomitant injuries.

  • BTB (Bone-Tendon-Bone):

The name BTB technique comes from Bone-Tendon-Bone and means that the transplant consists of a bone block, a section of tendon and another bone block.

The tendon used in this technique is the patellar tendon, i.e. the tendon that connects the patella to the lower leg and therefore has an important extension function.

The advantage of this technique is the high tractive force of the tendon used and the fact that the bone blocks heal very quickly and the patient therefore achieves optimal stability of the knee joint very quickly and therefore can be reintegrated into training relatively soon.

The disadvantage of the technique is that patients complain of pain at the extraction sites of the bone blocks (anterior knee pain) at a rate of approx. 10%, predominantly during activities that involve kneeling. Moreover, complications such as patellar fractures and tendon tears are described. The main problem with the method, however, is that long-term studies clearly prove that almost all patients with a BTB transplant demonstrate more or less pronounced retropatellar arthrosis (= cartilage damage behind the patella) after 20 years.

The operation begins with arthroscopy (any meniscus or cartilage damage that may be present is also treated at this time) and removal of the remnants of the torn cruciate ligament.

The bone is debrided in the areas of attachment of the cruciate ligament. Many surgeons now make a larger incision over the tendon, through which the whole operation area is viewed and the tendon can be recovered. As injuries to nerves with a feeling of numbness often occur, I prefer two small incisions over the bone blocks and recovery of the middle section of the tendon and sections of bone (bone blocks approx. 1.5 cm in length and 8 mm wide from the tip of the patella and the tibial plateau) using a minimally-invasive technique (keyhole technique).

The drill holes for the attachment of the bone blocks in the region of the former attachment and origin of the anterior cruciate ligament are then carried out, the cruciate ligament is then inserted and fixed into its location using special screws (interference screws made from titanium).

Immobilisation of the knee is only required in the case of concomitant injuries.

  • Synthetic ligament:

To avoid destroying the autologous receptors and also to avoid the disadvantages of the aforementioned methods, an synthetic ligament (LARS) can also be used in certain cases (if a good cruciate ligament stump is available). In this technique, the synthetic ligament should not replace the cruciate ligament (that would not function in the long-term), but rather stabilise the cruciate ligament until it is healed. Numerous studies have shown in recent years that the results using this synthetic ligament are very good and the complication rates are very low (if it is used correctly). If placed incorrectly, however, problems can develop rapidly - this method should therefore only be used by experienced knee surgeons (who are also trained in this technique).

An indication that presents an exception for the synthetic ligament are athletes for whom several operations have failed, and in whom the synthetic ligament is then used as a cruciate ligament prosthesis; or older people with unstable knee joints, who do not have very good tendons of their own, yet they still want to remain active in sport.

  • Quadriceps tendon:

this section of tendon placed over the patella is used in revision operations if STG and BTB have already been removed or are not available for other reasons.

Posterior cruciate ligament

Injuries to the posterior cruciate ligament mainly occur as the result of significant trauma, such as car accidents or ball sports (American football, handball, etc.).

These injuries are essentially rare for a tear of the anterior cruciate ligament and can be healed surgically but also without an operation. The operation depends on the degree of instability, the symptoms and primarily the sporting requirements of the patient.

In the case of fresh injuries, the use of the synthetic ligament (LARS) is extremely promising and gentle for the athletes affected. In chronic cases, I use a quadriceps tendon in the inlay technique or an STG transplant (see above for removal, advantages and disadvantages, etc.)

Cruciate ligament injuries in children


Cruciate ligament injuries in children are rare and are therefore often initially overlooked in the investigation. It is important that specialists carry out an investigation into persisting symptoms and an MRI in all cases. The majority of children are initially immobilised using a splint, so that the anterior cruciate ligament has the opportunity to heal (this also works in approx. 50% of cases). Another clinical examination is carried out six to eight weeks after injury and another after approx. three months. If the knee joint remains unstable, early operation is recommended to the parents and the child, as additional injuries to the menisci and cartilage occur very frequently, due to the high activity potential of children - which sets a course for rapid and premature destruction of the knee.

Cruciate ligament injuries in the elderly


Cruciate ligament injuries in the elderly are rare and are often not operated on due to the predominantly low degree of activity. The primary treatment is immobilisation and muscle strengthening (physical treatment) - old and untreated cruciate ligament injuries with complications (arthrosis) are often the problem. The increasing number of senior citizens who are very active, who want to go hiking in the mountains with a stable knee or battling on the tennis court, is an exception. This group obviously needs a stable cruciate ligament and the method should be discussed on a case-by-case basis (STG or synthetic ligament)



50% of operation successes are achieved by means of subsequent rehabilitation and physical therapy. Full range of movement, muscle strength and coordination are only regained with this appropriate postoperative treatment.


Please note that medical indications and treatments change constantly. Sometimes these changes occur more rapidly than I am able to update on my homepage. Some information regarding dosage, prescription and compositions of medications may have changed in the meantime. Reading an internet page cannot replace visiting a doctor - it may be that during an examination and subsequent discussion with your doctor, other information is also communicated as a result of new scientific knowledge.