Anatomy

Structure of the knee:
Bones and cartilage
The knee joint is made up of 3 bones – the femur (the thigh bone), the tibia (the larger shin bone) and the patella or kneecap. The patella is 5-7 cm wide and 7-10 cm long. It sits in front of the other bones in the joint and slides over the femur when the knee moves. It has a protective role over the knee and acts as a support for the muscles.
The ends of the bones in the joint are covered with articular cartilage – this is a strong, elastic tissue that absorbs shock and allows smooth movement in the knee. The menisci are made of connective tissue, divided into two sickle-shaped disks and positioned between the tibia and femur on the inner and outer portions of each knee. The two menisci at each knee absorb shock, cushioning the calf from the weight of the body and increasing stability.

Musculature

There are two types of knee muscles. The quadriceps muscle comprises four muscles in the anterior portion of the thigh and helps with the extension movement of the leg (straightening the leg from a bent position). The muscles in the posterior box of the thigh perform the flexion movement of the leg.

Link

Ligaments are strong, elastic bands that connect bones together. They bring stability and strength to the joint. There are 4 ligaments that connect the femur to the tibia:
– medial collateral ligament: provides stability in the medial (medial) portion of the knee
– lateral collateral ligament: provides stability in the lateral (lateral) portion of the knee
– anterior cruciate ligament: located in the center of the knee, it limits the rotation and anterior movement of the tibia
– posterior cruciate ligament: located in the center of the knee, it limits the posterior movement of the tibia.
The knee capsule is a protective fibrous structure surrounding the knee joint. Inside the capsule, the joint is lined with thin, soft tissue called synovium.

Tendoane

Tendons are strong cords that connect muscle to bone. At the knee, the quadriceps tendon connects the quadriceps muscle to the patella and provides the strength for the extension movement. The patellar tendon connects the patella to the tibia. It is technically a ligament, but is commonly called a tendon.

Description

The anterior cruciate ligament, or ACL, is located in the center of the knee, along with the posterior cruciate ligament, or PCL. These ligaments are tightly anchored to the femur and tibia to form a criss-crossed structure in the knee that prevents the bones from moving forward or backward.

The anterior cruciate ligament (ACL) is the most commonly damaged knee ligament. Annually there are an estimated 200,000 cases of ACL injuries, with 100,000 cases of ACL reconstruction performed annually. In general, injuries that result in knee ligament damage are higher in people who play high-risk sports such as basketball, soccer and skiing.

Approximately 50% of LIA lesions occur in association with damage to the meniscus, articular cartilage, or other ligaments. In addition, patients may also have lesions on the cartilage surface. These can be seen on magnetic resonance imaging (MRI).

ACL injuries are usually sports-related. However, spraining, straining or tearing of the ACL can also be caused by repetitive physical stress, such as excessive pivoting or twisting of the knee.

Injury to the cruciate ligaments may not cause pain. Rather, the patient may only hear a noise in the joint and the leg bends when attempting to orthostatically (standing) due to lack of stability.

Causes

It is estimated that 70 percent of LIA injuries occur through mechanisms without direct contact, while 30 percent occur as a result of direct contact with another player or object.
Several studies have shown that female athletes have a higher incidence of AIS than male athletes.This is due to differences in physical fitness, muscle strength and neuromuscular control.
Immediately after the injury, patients usually experience pain and swelling, and the knee feels unstable. Within a few hours after an ACL rupture, patients experience swelling of the knee, loss of mobility, pain or tenderness along the joint line and discomfort while walking.

Ligament injuries occur when the knee joint is flexed and rotated (the chances of injury are higher when these movements are associated), or in case of a hard contact: the foot is fixed to the ground and a sudden force hits the knee from the outside, when it is bent or slightly flexed (hit by a person or an object).
Injury to this ligament is common in sports that involve rapid changes of direction, repeated stops and runs or jump landings, such as soccer, rugby, basketball, skiing, gymnastics, martial arts.
Missing a step when going down stairs or stepping into a pothole can also result in ACL injury.
The strength of the anterior cruciate ligament gets weaker with age, which is true for any other body part. So tears occur more easily in people over 40.

Examination by the doctor

When a patient with an ACL injury presents to the doctor, he or she will carry out a clinical assessment and an X-ray may be recommended to check for a possible fracture. The doctor may also order a magnetic resonance imaging (MRI) scan to evaluate the LIA and to check other knee ligaments, menisci, or articular cartilage.

In addition to performing special tests to identify injuries to the meniscus and other ligaments in the knee, the doctor will often perform the Lachman test to see if the ACL is intact.

If the ACL is broken the tibia has a greater anterior displacement relative to the femur than the healthy knee.

Another test to check for LIA injury is the pivot shift test. In this test, if the LIA is torn, the tibia will go forward of the knee when the knee is in a completely straight position and then shift back to the correct position relative to the femur when the knee is bent at 30 degrees.

Natural history

The natural course of an LIA lesion without surgery varies from patient to patient and depends on the patient’s activity level, degree of injury and symptomatic instability.

The prognosis for a partially ruptured LIA is often favorable, requiring approximately three months to recover. However, some patients with a partially ruptured LIA may still have symptoms of instability.

Complete tears of the LIA may have a less favorable outcome. After a complete tear of the LIA most patients are unable to participate in sports that require pivoting movements on the affected leg, but there are also patients who present knee instability when walking. There are some people, a small number, who can play sports without any symptoms of instability. This variability is related to the initial severity of the knee injury as well as the physical demands of the patient.

About half of all ACL injuries occur in association with damage to the meniscus, articular cartilage or other ligaments. Secondary damage may occur in patients who have repeated episodes of instability due to the LIA. With chronic instability, up to 90 percent of patients will have meniscal damage after a reassessment 10 years after the initial injury. Similarly, the prevalence of articular cartilage damage increases by up to 70 percent in these patients.

Non-surgical treatment

In non-surgical treatment, progressive physiotherapy can bring the knee to a near normal state.It is also important to educate the patient on how to prevent instability. This can be supplemented with the use of a mobile knee orthosis. However, many people who choose not to have surgery may have secondary knee injuries due to repeated episodes of instability.

Surgical treatment is usually recommended in combined lesions (LIA lesions in combination with other knee lesions). Nonsurgical treatment of isolated LIA lesions may be successful or may be indicated in patients with:

– with partial injuries and no symptoms of instability
– with complete injuries and no symptoms of knee instability during low-intensity sports activities, and who are willing to give up high-intensity sports
– people who do light manual work or live a sedentary lifestyle
– those with open growth plates (children)

Surgical treatment

LIA injuries are not usually repaired using suture, because repaired LIAs have generally been failed surgeries over time. Therefore, the ruptured LIA is replaced with a tendon substitute graft. Grafts commonly used to replace LIAs include:

– patellar tendon autograft (autografts come from the patient)
– semitendinosus and gracilis tendon autograft (the most common method used)
– quadriceps tendon autograft
– allograft (taken from a cadaver) of the patellar tendon, Achilles tendon, semitendinosus, gracilis, or posterior tibial tendon.
Patients with surgical reconstruction of the ACL have a long-term success rate of 82-95 percent. Recurrent instability and graft failure are seen in about 8 percent of patients.

The goal of ACL reconstruction surgery is to prevent instability and restore function to the torn ligament, creating a stable knee. This allows the patient to return to pre-injury sports activities. There are certain factors that the patient should consider when deciding for or against ACL surgery.

Patients

Adult patients who play sports or have jobs that require a lot of force or heavy manual labor are candidates for surgery. Activities of daily living, not age, should be considered in determining whether surgery is appropriate.

In young children or adolescents who have LIA injuries, LIA reconstruction surgery can be a risk in their physical development. The doctor may postpone the surgery until the child is closer to skeletal maturity, or, the surgeon may modify the technique of LIA surgery to reduce the risk of damage to the growth plate.

A patient with a ruptured LIA and significant knee instability is at higher risk of secondary injuries and therefore LIA reconstruction should be considered.

Percentage: 50 percent of patients with ACL injuries have associated meniscus injuries, 30 percent have articular cartilage injuries, 30 percent have collateral ligament injuries, and 30 percent have articular capsule injuries. The “unhappy triad” is frequently seen in soccer players and skiers, and represents lesions of the ACL, medial collateral ligament and medial meniscus.

Surgical options

Patellar tendon autograft.The middle third of the patient’s patellar tendon, along with a fragment of bone from the tibia and patella is used in the patellar tendon autograft. It is sometimes referred to by some surgeons as the “gold standard” for LIA reconstruction, and is often recommended for performance athletes and patients whose jobs do not require overuse of the knee.

In studies comparing the outcomes of patellar tendon and “goos paw” tendon autograft with semitendinosus and gracilis tendon, the failure rate for graft was lower in the patellar tendon group (1.9 percent compared with 4.9 percent).

In addition, most studies show equal or better results in postoperative tests for knee laxity (Lachman, anterior drawer and instrumentation tests) when patellar tendon grafting is used compared to others. However, patellar tendon autografts have a higher incidence of postoperative pain (pain behind the patella), discomfort and other problems.

The pitfalls of patellar tendon autograft are:
– postoperative pain behind the patella
– generalized knee pain
– slightly increased risk of postoperative knee stiffness
– low risk of patella fracture
Semitendinosus and gracilis tendon autograft. The semitendinosus tendon that lies on the inside of the knee is used in the creation of hamstring tendon autograft for ACL reconstruction. Some surgeons use an additional tendon, the gracilis, which is attached below the knee in the same area. Supporters of the hamstring autograft say there are fewer graft harvesting problems compared to the patellar tendon autograft, namely:

– fewer problems with anterior knee pain or generalized knee pain postoperatively
– fewer problems with knee stiffness postoperatively
– smaller incisions
– faster recovery

Graft function may be limited by the strength and type of fixation in the bony tunnels, as the graft grafts the semitendinosus and gracilis tendons without bone sockets. But it still remains the most commonly used method for LIA reconstruction.