Introduction

Knee ligament repair is a surgical procedure to reconstruct or repair torn or injured ligaments in the knee. These ligaments are crucial for the stability, mobility (movement), and functioning of the knee joint. A knee has four ligaments: two cruciate and two collateral or side ligaments that support the knee joint and protect it from injury or being twisted. Torn knee ligaments or knee injuries are common among athletes. 

The anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), medial collateral ligament, and lateral collateral ligament are crucial ligaments for the knee. The medial and lateral collateral ligaments help to stabilise the knee when the leg is straight. The anterior and posterior cruciate ligaments work when the knee is bent, and the other two collateral ligaments relax. 

Sports activities and sudden or improper landing can cause ligament injury, which causes extreme pain, swelling, and an inability to stabilise.¹ This article will explain the anatomy of knee ligaments, the causes, symptoms, and diagnostic methods of injury, along with treatments.

Anatomy of knee ligaments

Knee ligaments consist of bands of tissues connecting the thigh bone to the lower leg bones. Ligaments are made of collagen, connective tissue, and elastic fibres. They are categorised into two groups: cruciate ligaments and collateral ligaments. Collateral ligaments are like straps on each side of the knee and prevent knees from excessive side-to-side movement. Cruciate ligaments are inside the knee joint and connect your femur bone to the tibia. These ligaments control the front-to-back movement of the knee. Anterior cruciate ligament (ACL).

ACL prevents knee hyperextension and also prevents the tibia from sliding forward. It saves from posterior femoral displacement and anterior tibial displacement.

Posterior cruciate ligament (PCL)

It tightens during knee flexion (an act of decreasing the angle between the lower leg and thigh, helping to bend the knee) and prevents hyperflexion and posterior tibial displacement. PCL aids in maintaining body weight when the knee is flexed or prevents the tibia from sliding backward.

Medial collateral ligament (MCL)

MCL is also known as the tibial collateral ligament (TCL). This is firmly attached to the medial meniscus and prevents valgus stress (movement used to diagnose ligament injury) on knees or knocked knees.²

Lateral collateral ligament (LCL)

The LCL, also known as the fibular collateral ligament (FCL), manages varus stress on knees or bowed knees. These are bands of tissues located outside the knees.

Causes of knee ligament injuries

Knee ligaments are bands of tissues connecting one bone to another. The ACL crosses the middle portion of the knees and connects the thigh bone to the tibia. However, an injury to the ACL or other knee ligaments destabilises the knee joint. Often, knee ligament injuries take place during sports and other activities that exert stress on the knee, such as:

Trauma and sports injuries

• Common in high-impact sports like football, basketball, and soccer, which involves jumping, running, and stopping with rapid changes in direction
• Knee injuries can happen from falling

Twisting or hyperextension

• Sudden pivoting or awkward landings that strain or tear ligaments
• Suddenly changing direction (cutting) or slowing down
• Moving the knee beyond the usual range of movement

Direct impact

• Blows to the knee, often seen in contact sports or accidents
• A direct blow to the knee or a collision, for instance, a football tackle
• Avoiding precautions while exercising, such as no warm-up before doing any activity or not cooling down later

A knee ligament injury may occur if a person has knee osteoarthritis, which causes weak muscles around the knee joint and increases the risk of a knee injury.³ Any damage to the ligament usually results in a partial or complete tear of tissues. In a mild injury, the ligament may get stretched but left intact. Ligament injury often comes with sudden pain and other symptoms, which will be discussed.

Symptoms of knee ligament injuries

The symptoms of knee ligament injury vary depending on the impact on a particular part of the knee. For instance, a torn knee ligament includes symptoms like:

• Knee pain with swelling and instability or inability to walk
• One may feel or hear a popping sound at the time of injury to the ligament
• Unable to put full body weight on the legs
• Injury in a knee meniscus may cause:
  • Severe pain and swelling in the knee after a few hours
  • Locked knee with lack of usual movement
  • Ability to walk a little on legs 
  • Weight-bearing becomes difficult or impossible
• Tear in tendons may present knee pain and swelling along with:
  • Displaced kneecap
  • Inability to lift the knee
  • Knee pain becomes worse while bending the knee

In addition to the above symptoms, an infection may produce redness on the knees and feelings of hotness with pain.⁴ The severity of the injury can be detected with the help of various diagnostic methods mentioned ahead. 

Diagnosis of knee ligament injuries

During the physical examination of the injury, a doctor checks swelling and tenderness on the knee and compares the injured knee to the uninjured one. You may be asked to move the knee into various positions to assess a range of motions and the overall functioning of the joint. Usually, a diagnosis can be made based only on the physical exam. Still, tests are required to eliminate other causes and determine the severity of an injury. These tests may include:

X-rays

X-rays are needed to detect a bone fracture. However, soft tissues like ligaments and tendons are not visible clearly in X-rays.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) generates images of both hard and soft tissues in a body. The MRI scan can provide the level of an ACL injury and possible damage to other knee tissues, such as cartilage.

Ultrasound

Ultrasound uses sound waves to visualise internal structures. It can be used to examine injuries in the muscles, ligaments, and tendons of the knee.

Lachman Test

Often, the Lachman test is used to assess ACL rupture.⁵ The healthcare professional positions you in such a way that stabilises the thigh bone using one hand and the other hand to pull the tibia forward. A positive test provides increased anterior tibial translation relative to the femur.³

Pivot shift test

The pivot shift test is used to assess ACL rupture and associated injuries. The pivot shift test is a helpful physical examination to diagnose rotatory instability associated with ACL tears.⁶

The knee ligament repair process, be it surgical or home treatment, is decided based on the severity of the injury, which is diagnosed using various tests. Healing from ligament tears may take time and can be hard, but the lack of an appropriate treatment process mentioned below may cause trouble.

Treatment methods

Treatment of a knee ligament injury starts with a physical examination followed by different tests. There are multiple factors to be considered, such as the individual’s age, activity level, extent of injury, sports participation, and stabilising structures around the injured portion before deciding on treatment or management. Surgical or nonsurgical treatments are used based on the severity of knee injuries, which are categorised into different grades:

Grade 1

Grade 1 knee injuries are mild, and the ligament is not completely torn. You can heal with at-home treatment, involving the use of crutches. It takes three to four weeks to heal.

Grade 2

Grade 2 knee injuries are considerably moderate, with a partial ligament tear. In grade 2 injury, crutches and a hinged knee brace are used. Recovery requires approximately eight to 12 weeks.

Grade 3

Grade 3 knee injuries are considered severe, and the ligament is separated or torn completely. It may take eight to 12 weeks for healing, and a hinged brace is used for several months. 

Individuals with grade 2 or grade 3 type injuries are treated with surgical techniques, while grade 1 injuries can be treated without surgeries.

Surgical techniques

Surgical techniques are arthroscopically assisted with the preparation of the graft bed. The surgeons may remove the injured tissues or ACL remnants completely or partially (stump). The surgeons leave the stump to promote tibia tunnel positioning or ACL placement with greater healing.

Arthroscopic surgery

• Minimally invasive technique using a camera (arthroscope) and small incisions
• A small tube-shaped tool is inserted into a joint
• A surgeon may reattach or reconstruct the torn ligament using a part (graft) of the patellar tendon (connects the kneecap to the tibia), hamstring tendon (back of the thigh) or other parts

Graft options

An autograft is a tissue, patellar tendon, or hamstring harvested from the individual undergoing surgery. Autografts carry a lower risk of graft re-rupture in young athletes, four times less than allografts.⁷ 

An allograft is the tissue taken from another person or donor. Allografts are expensive and take more time to incorporate with a risk of disease transmission. The use of allograftsfor primary reconstruction has two times more risk of re-rupture compared to use in revision cases.⁷

Open surgery

• Used in more complex cases or when multiple ligaments need repair
• Implemented in severe injuries to stitch torn ligaments or reattach them to the bone and reconstruct the ligament with the use of tendons or other ligaments
• Multiple ligament injuries may require open surgery for reconstructing multiple ligaments in a single surgery

Non-surgical technique

People who don't do a lot of physical activity or athletes who play sports that don't require ACL laxity (an abnormal rotation of the tibia with respect to the femur), cutting (like quick direction changes in tennis), or pivoting (like quick turns on one foot in basketball) can get help without surgery. 

In non-surgical techniques, individualsare usually treated with physiotherapy and lifestyle modifications. 

In partial ACL tears, these can be implemented. An acute symptomatic treatment is involved in this, proceeding with supervised physiotherapy for 12 weeks. This results in recovering a full range of motion as well as core muscle strengthening. 

Historically, non-surgical management was the first line of treatment for isolated ligament injuries regardless of the severity of the injury. The acute treatment used includes RICE (rest, ice, compression, and elevation) and intake of nonsteroidal anti-inflammatory drugs (NSAIDs).⁴

In cases of severe tears, direct repair of the torn ligament or using sutures to reattach is involved. However, post-treatment assessments to evaluate recovery progress should be performed.

Post-treatment recovery and risk

Physiotherapy (physical therapy) is essential for post-treatment recovery to strengthen your muscles and increase the range of motion. The measures essential for recovery and rehabilitation after knee ligament repair include:

Post-surgical care

• A brace or cast is used to immobilise and stabilise the knee
• Medications are used to manage post-surgery pain and swelling

Physiotherapy/physical therapy

• The initial phase of physiotherapyfocuses on regaining motion, reducing swelling, and preventing muscle atrophy
• Strengthening and range of motion exercises gradually revive strength in the knee and surrounding muscles
• Balance and stability training are helpful to restore knee function and prevent future injuries

Return to activity

Full recovery and return to sports or participation in high-intensity activities typically take six to 12 months, depending on the injury and rehabilitation progress.

In addition to this, there are various risks and complications that may occur during knee ligament repair, such as:^8,9

• Superficial infection and septic arthritis may occur from graft contamination or any other infection during operation/surgical handling, like falling on the floor that can be cleaned with various antibiotic solutions without risk of infection
• Risk of deep vein thrombosis (DVT) from blood clots after surgery
• Stiffness and loss of motion are the most common complications after ACL reconstruction caused by a preoperative limited range of motion, and regaining full range of motion after surgery may be difficult
• Graft failure can be due to various issues: hardware failure, inadequate fixation caused by screw divergence, or small graft diameter; the graft may not heal properly or could re-tear; improper rehabilitation or too aggressive exercises may also lead to graft failure¹⁰
• Tunnel malpositioning is the placement of a vertical tunnel in the vertical plane on the femoral side, instead of the horizontal plane, that will cause persistent rotational instability in patients

A mild knee ligament injury heals easily. However, in moderate to severe cases, treatment and recovery are equally important. Moreover, a moderate injury can become serious due to lack of care. Consequently, after treatment, recovery involves progressive steps such as starting with simple activities to gentle exercises (stretches). Then, move on to moderate ones and finally return to normal activities while consulting the healthcare professional.

Summary

Knee ligaments are one of the most crucial parts of our body that manage the overall weight. Any injury to knee ligaments should be diagnosed and treated appropriately, whether in ACL, PCL, MCL, or LCL. The causes of such injuries can be sports and accidental twisting or hyperextension, but these can be prevented by strengthening muscles around the knee and proper conditioning to reduce future injury risk. Repair of ligaments after injury is crucial for restoring knee stability and function following severe injuries. Depending on the severity, ligament injuries can be managed non-surgically or surgically. The outcomes for patients affected by knee ligament injuries are good, and further recovery can be enhanced using physical therapy.