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With increasing popularity for a variety of physical activities, the number of injuries also increases. The knee joint is one of the most exploited joints in the body, and therefore is a place of frequent problems. Damage to the knee joints most often happens to physically active people. Depending on the size of the external force affecting the joint and the mechanism of injury, there are stretches, sprains, bruises, but also tears or complete rupture of muscles or ligaments.


The knee joint has numerous ligaments that are responsible for its stabilization. You can divide them into external and internal ligaments:

  • external ligaments – patellar tendon, tibial lateral ligament, fibular ligament, popliteal ligament
  • internal ligaments – frontal cruciate ligament (ACL), posterior cruciate ligament (PCL) and transverse ligament of the knee

One of the main stabilizers of the joint is the frontal cruciate ligament, the injury of which is most exposed to people practicing skiing, football or basketball, that is, sports with high torsional movements (pivot).


Front anterior ligament – anatomy and role

The anterior cruciate ligament, often referred to as the abbreviation ACL – anterior cruciate ligament, is a structure that begins on the inner surface of the lateral femoral condyles (posterior margin) and runs obliquely downwards and medially ending in the anterior intercondylar area of ??the tibia.

The ligament consists of two tufts, the antero-medial (superficial part, much more likely to be injured), which is responsible for the change of the rolling movement to the slide and the posterior-lateral bundle.


The average dimensions of the ligament are approximately 4cm in length and 1cm in width. The ligament is nourished by the mid-artery of the knee and the lower knee arteries (in most ACL injuries there is bleeding inside the joint, as a result of the interruption of the artery continuity), whereas the innervation provides the articular nerve. The main building component of the ligament is water (60%) and collagen (35%) and, to a small extent, also elastin (5%).

ACL has numerous receptors in its structures:

  • Pacini bodies – receptors of touch, pressure and vibration
  • Golgi body – the largest receptors of the knee joint, activated during the strong extension of the ligament and the border state of tension
  • Ruffini cells – they inform about the joint’s position and limb movements
  • free nerve endings – they act as pain receptors, which activate when damaging the pond

The frontal ligament connects the tibialis with the femur, prevents the tibia from moving forward and tibial rotation in relation to the femur. This mechanism works with every possible bending of the knee. The ligament additionally limits excessive extension and bending of the knee joint as well as exaggerated collapse and deformation of the joint in the upright position, flexion and internal rotation.

The second equally important role that the frontal cruciate ligament fulfills is the transmission of information from its receptors, thanks to which it is possible to react quickly to suddenly appearing threats to the joint.


Mechanism damaging the ACL ligament

Damage to the anterior cruciate ligament is one of the most common injuries in the knee. Damage mechanisms are many, but the most common are two:

  • rotational – with the stabilized foot and slight bending of the knee, the torso suddenly twists, which causes high tension of the ligament and often its damage (skiing)
  • straight – tibial stroke with the knee straight (playing football – sliding)


Symptoms indicating damage to the anterior cruciate ligament:

  • severe pain at the time of injury, which tends to gradually disappear
  • feelings of instability and uncertainty of the knee (“running off of the knee during loading which leads to faster exploitation of the joint)
  • periodic subluxation of the knee joint (leads to damage to the articular cartilage on joint surfaces and menisci, as well as the formation of bone growth)
  • swelling, exudation (sometimes appear late, up to 24 hours)
  • blood in the synovial fluid
  • positive results in clinical tests: Lachmann, front drawer and pivot shift


ACL reconstruction

The total rupture of the ligament makes it impossible to spontaneously regenerate fibers. Medical intervention is required, which usually involves a reconstruction of the ligament or contraindications to the procedure, conservative treatment. Each procedure is preceded by a test and qualification for the procedure, where the reconstruction indications are:

  • presence of clinical symptoms of knee instability
  • subjective feelings of joint instability (“knee escaping”)
  • young age – in young subjects, the indication of qualification for the procedure is the statement of the rupture of the ligament, without the need for other symptoms
  • level of physical activity
  • interruption of the ligament

The reconstruction surgery consists in reconstructing the ligament, which restores the joint stability in the full range of motion. For the reconstruction of the ligament, the patient usually uses a transplant from the patient – the tendon of the semi-sinewy or slender muscles, sometimes also the section of the ligament of the right patella. The collected graft is fixed in the tibial and femoral tibial channels with anchors or screws.

Lack of qualifications for surgery requires the introduction of conservative treatment, which is primarily aimed at improving muscle stabilization by strengthening muscle strength and deep sensation, and work on neuromuscular coordination.


Preparation for the reconstruction surgery – preoperative rehabilitation

An important stage of the procedure is preoperative rehabilitation, which is aimed at preparing the knee joint and the patient himself to function in new conditions. Reconstruction of ACL is a planned treatment, with a different waiting period (from several weeks to several months), which gives the patient time to prepare the limb for surgery.

Depending on the extent of the injury, it is important to compensate for periarticular lesions, edema or inflammation. It also happens that knee arthroscopy is required to remove the intra-articular hematoma or damaged part of the meniscus.

Physiotherapy before surgery is aimed at:

  • achieving the maximum range of flexion (120?) and extension (0?) in the knee joint
  • reduction of edema and inflammation
  • strengthening the muscles in the lower limb (mainly the quadriceps – medial head) – preventing muscle atrophies, which appear as a consequence of immobility.
  • learning to walk on crutches and controlled loading of the lower limb

It is also a time for patient education in the field of rehabilitation that will be carried out after surgery.

Bending contraction in the knee joint (no full extension of the knee) may be a contraindication for ACL reconstruction.


Post-operative treatment

Rehabilitation after reconstruction of the anterior cruciate ligament can be divided into several stages, which have different goals and assumptions, and also differ in the methods of work. Immediately after the procedure the early postoperative phase begins, which lasts about 2 weeks – until the sutures are removed.

1-4 days

The procedure is aimed at reducing exudate, inflammation and pain. It is used to cool the joint every 1.5-2 hours, elevation position of the limb (foot above the knee, knee above the hip), as well as pharmacotherapy. In order to reduce swelling, lymphatic drainage is performed.

Another element of the procedure are exercises preventing postoperative adhesions and limiting the range of motion. Is moving in :

  • isometric exercises (muscle tension without movement)
  • passive exercises conducted using the CPM bus in the range of 0?-45? (each session lasts about 60 minutes – even 3 times a day)
  • passive exercises conducted with a therapist
  • self-assisted bending exercises in the knee joint
  • myofascial work on scars – much attention should be paid to the place from which the transplant was obtained

There are large discrepancies as to the recommendations for loading the lower limb after the procedure. It is related to several factors that determine a faster or later load:

  • extent of injury (damage to other joint structures)
  • time from injury to surgery
  • age and level of patient’s efficiency
  • surgery technique

Due to the fact that today the techniques of reconstructing the ligaments are very stable and durable, many centers recommend early loading of the lower limb. That is why in the first period the patient is in a vertical position and the learning of walking is carried out on crutches with full limb load, within pain tolerance.

In the early postoperative period, additional:

  • stretching of the ischio-shin group
  • gentle patellar mobilization


The patient after the procedure usually stays in the institution for 1-3 days. Initially, the patient moves on crutches, to improve the walking pattern, reduce pain and reduce swelling. Rejection of the ball is possible within 4-10 days after the procedure, if the patient does not feel pain, the pattern of gait is not disturbed and the patient has adequate neuromuscular control.

4-14 days

In the second stage proceeding from the first period is continued, i.e. anti-oedematous, antithrombotic action, as well as work on the scope of mobility and correct movement patterns:

  • cooling the pond, compression and elevation
  • striving for a full extension of the knee joint through passive exercises with a therapist, self-assisted exercises, extension of the ischioles and hip and tibia band, and more intensive kneecap mobilization
  • active exercises of gluteal muscles, adductors as well as the ischio-shin group, both lying and standing
  • Proprioception exercises in a standing position, on a stable surface, and with the use of a ball (eg, pressing the ball with your foot into the wall) 

2-6 weeks.
This is the period of return to normal everyday functioning, in which there are still proceedings aimed at regaining full mobility, correct patterns of movement and gait, as well as the ability to perform basic activities of everyday life.

  • cooling the joint – recommended especially after physical activity
  • increasing the range of bending movements up to 90?


The period between 6 and 12 weeks is the time when the grafted ligament “rebuilds” itself with its own tissue. There is redevelopment and revascularization (reconstruction of the blood vessel network), which, however, makes the ligament very susceptible to stretching. Therefore, this is the time when you should avoid sudden twisting movements, as well as long stay in the position of maximum extension of the joint (large bend).


  • Proprioception exercises – various devices are used that provide an unstable base (balls, equivalent discs). Exercises are performed in various positions, including standing on one leg.
  • Quadriceps strengthening exercises – isometric exercises are performed in various joint settings and squats (up to 60? maximum)
  • Active exercises of flexors, adductors and abductors
  • Riding a stationary bike, with a high saddle position

6-9 weeks

Each subsequent week of rehabilitation is associated with an increase in the intensity of exercise and the level of difficulty. It is also a time in which much attention is paid to improving the bending range in the knee joint (up to 120?).

Throughout the whole period, joint swelling control, manual mobilization of the patella in all directions, as well as control of normal movement patterns are recommended.

The technique of doing exercises (avoiding knee deformity and excessive rotation) and avoiding exercises in the maximum range of flexion (deep squat, stretching of the quadriceps in a large extent) require a lot of attention.

An important stage of the procedure is the proprioception training, which at this stage includes both static and dynamic exercises. More and more demanding ground is being introduced – mattress, equivalent disc, Bos ball, trampoline.

In addition, between the 6th and 9th week, it is recommended to:

  • riding a stationary bike, with gradual lowering of the saddle, which forces a larger knee bend
  • stepper (small range of movement)
  • resistance exercises for flexors of the knee joint – with gradually increasing resistance, in the range of 20?-90?
  • concentric and eccentric exercises for the quadriceps muscle – sitting and getting up from the sit (slowly), as well as entering and leaving the stage

9-12 weeks

This is the time to return to physical activity and the phase of intensive strengthening of the lower limb muscles. The goals in this period include achieving the full range of mobility and muscular strength and endurance, as well as introducing individual elements of the sports discipline.

Exercises from previous stages are performed, but in a larger range of mobility and with increased external load (weights, resistance belts) – squats, trips, jumps. In the proprioception exercises there is more and more dynamics and more and more unstable ground (exercises on berets, batucie, dynamic jumps, forward trips, rope training, running in a place on unstable ground).

12-16 weeks

The following weeks are characterized by the inclusion of increasingly difficult elements for exercise – riding a bike in the field, jogging in the field, as well as strength exercises with increasing resistance. Gradually there are also elements of the sports discipline – learning to move, dynamic returns, braking or quick start.

The range of motion and dynamic proprioception exercises are continued.

16 – …

From the 16th week there is a gradual return to sports activity, however, the rehabilitation program is continuing all the time, including: strength and endurance training, dynamic proprioception exercises and coordination as well as exercises improving the range of mobility. A very important aspect of the training is correct exercise technique, it should be observed against knee deformation or excessive external / internal rotation.

Return to full sporting activity follows the functional tests that evaluate the efficiency of the lower limb. The correct test result should be about 85% relative to the other limb. The choice of tests depends on the patient’s fitness and condition, they may include: stepping into a step, squat one-legged, getting up from one chair, jumping one-legged forward, back and sideways.

Return to full sporting activity usually takes about 6-9 months after surgery. The conditions for full limb loading during intense activity are:

  • full range of mobility in the knee joint (painless)
  • joint stability
  • functional tests – at least 85%
  • the ability to perform complex movements characteristic of the discipline without pain



The main goal of rehabilitation after reconstruction of the anterior cruciate ligament is to restore the function of the knee joint, understood as regaining full mobility, proprioception, coordination and muscular strength, as well as a return to full fitness as soon as possible.

The rehabilitation program is adapted individually, which is related to the patient’s activity level, sometimes from trauma to surgery and surgical technique. The selection of exercises and intensity depends on many factors, including very important – no pain during exercise.

Transplanted ligament goes through a series of changes that ultimately lead to remodeling into a new ligament. The process lasts about 3 years, but the most intense changes take place between 6 and 12 weeks. This is the time when the ligament is least resistant to mechanical stress, therefore, the position of the graft should be avoided. However, small, repeated stresses are indicated, which stimulate the formation of collagen, thereby strengthening the ligament.

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