Unfortunately, anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) reconstruction sometimes fails miserably for both patients and surgeons and often requires complex revision surgery. It can fail for many reasons, such as poor initial graft placement, re-rupture of the graft, infection, or inadequate rehabilitation.

Symptoms of failed ACL and PCL reconstruction are similar to those of the original injury. Patients experience recurrent knee instability, pain, swelling, and a sensation of giving way during activities.

Revision surgery is the solution to restore knee stability. Preoperative planning is crucial, so a CT scan is always requested in addition to the MRI to assess the integrity of the graft, the position of the tunnels, and the presence of any other lesions.

The surgical approach and choice of graft depend on the reason for failure and the patient's anatomy.

If the tunnels are reusable or the previous tunnels were placed in a way that does not prevent new ones from being made, a revision is performed in one stage. In this surgery, a different graft from the previously used is taken, either the patient's own (autograft) or from a donor (allograft), and the ligament is reconstructed again with this tissue.

In case of large defects due to enlargement of the tunnels, a two-stage surgery may be necessary. In the first stage the tunnels are filled with bone graft and wait until it consolidates, on average between 4 and 6 months. In the second stage, the new reconstruction is performed.

If what failed was a primary repair, a reconstruction is performed normally.

Regardless of the type of failure and whether it is a one or two-stage revision, lateral reinforcement is always added to prevent further failures.

It is important to say that often the failure of cruciate ligament surgery is associated with a misalignment of the axis of the leg. In these cases, it is important to consider performing a corrective osteotomy.

The medial collateral ligament (MCL) and lateral collateral ligament (LCL) are knee stabilizers that arrest valgus (inward) and varus (outward) forces, respectively. The MCL is located on the inside of the knee and connects the femur to the tibia, while the LCL is located on the outside and connects the femur to the fibula. The posteromedial and posterolateral corners have a network of ligaments, tendons, and joint capsules that aid in rotational stability, of which the collateral ligaments are a part.

Injuries to these structures are usually due to direct trauma or forced twisting in a high-energy accident.

MCL injuries are caused by a blow to the outside of the knee and overstretching or tearing. Symptoms include pain, swelling, tenderness on the knee's inside, and instability when applying inward pressure. LCL injuries are caused by a blow to the inside of the knee and have similar symptoms on the outside, especially instability when outward pressure is applied.

The posteromedial and posterolateral corners are often injured by high-energy trauma and significantly alter knee stability. Injuries to these areas result in severe pain, swelling, and inability to bear weight. Patients may also present with bruising and inability to control knee motion.

The surgical options for these lesions are primary repair and reconstruction.

Primary repair is performed in acute injuries (first 4 weeks) with good tissue quality. In this surgery, the torn ligaments or tissues are reattached with sutures and fixed to the bone with anchors.

When primary repair is not possible due to time or extent of damage, reconstruction is necessary. This involves replacing the damaged ligament with a graft, either from the patient's tissue (autograft) or, more frequently in these injuries, from a donor (allograft). Tunnels are made in the femur and tibia on the internal side and in the femur, tibia, and fibula on the external side, through which the graft is placed and fixed.

Multiligamentary knee injuries are complex and severe injuries in which two or more of the major ligaments of the knee are injured at the same time.

These injuries are usually caused by high-energy trauma, such as traffic accidents or extreme sports, and result in significant instability and functional impairment of the knee joint.

The symptoms of multiligamentary injuries are severe and varied. Patients usually present with severe pain, severe swelling, and bruising around the knee. There is usually deformity and the knee is unstable and cannot bear weight. Patients may also feel that the knee gives way or buckles during movement. In severe cases, there may be vascular or nerve injuries that require immediate medical attention to avoid further complications.

Surgical treatment of multiligamentary injuries is aimed at restoring stability, function, and alignment of the knee.

Primary repair consists of directly suturing the torn ligaments back to their original position. This is applicable if the ligament injury is recent and the tissue is good. Early or immediate surgical intervention is often recommended to maximize the chances of healing and functional recovery. However, this is not always feasible, especially if there are associated vascular or nerve injuries.

Reconstruction is considered when primary repair is not possible, usually in chronic cases or when the ligament injury is extensive. It consists of replacing the damaged ligaments with tendon grafts, either from the patient (autograft) or from donors (allograft). For this, tunnels are made in the bones of the knee through which the tendons that will replace the function of the injured ligaments are passed and fixed.

In some complex cases with multiple injured structures (ligaments, tendons, menisci, joint capsule, cartilage, etc.), a two-stage surgery (two interventions on different days) may be necessary to safely address all injuries.

The menisci are two crescent-shaped cartilaginous structures located in the knee joint, specifically between the femur and the tibia. They act as shock absorbers, distribute weight, and improve knee stability. They receive blood in the peripheral zone (red zone), and the more central zone receives practically no circulation (white zone), with an intermediate zone (red-white) in which there is some flow.

Meniscal injuries, including tears, ramp injuries, and root avulsions, are very common and complex injuries of the knee. They occur during activities involving twisting or sudden changes in direction, such as sports, or due to degenerative changes in older adults.

Meniscal tears are the most common type of meniscal injury and can occur in different patterns: horizontal, longitudinal, radial, bucket-handle, or complex. Symptoms include pain, swelling, locking or catching sensation, and inability to fully extend or flex the knee. Ramp injuries are specific tears of the posterior horn of the medial meniscus that are often associated with anterior cruciate ligament injuries. Patients present with similar symptoms but with increased pain and instability. Root lesions refer to the tearing of the meniscus from its attachment site on the tibia, resulting in severe joint instability and dysfunction. This condition presents with acute pain, significant swelling, and mechanical symptoms that compromise the load-bearing capacity of the knee.

Surgical options for meniscus injuries aim at restoring knee function and relieving symptoms.

Repair is the ideal option for most meniscal injuries, especially those in the red and red-white zones, where the potential for scarring is greater and the volume of meniscus lost if removed is very high. The technique is based on passing "self-knotting" sutures inside the joint ("all-inside"), from the inside to knot outside ("inside-out") or from the outside ("outside-in") through the tissue to fix it and allow healing. These techniques are also used for ramp injuries. In meniscal root lesions, it is essential to perform a reinsertion. This surgery consists of passing threads through the torn root and a tunnel in the tibia and fixing them with an anchor in the bone so that the root is again attached to the bone. Meniscectomy is the resection of the torn meniscal tissue, and should only be performed in non-repairable tears.

It is common for a meniscal injury to require several suture passes, often combining several or even all of the described techniques.

In cases where an extensive meniscal resection has been performed, the knee loses much of its cushioning and begins to degenerate. In these cases, a meniscal transplant may be indicated.

Meniscal transplantation is an advanced surgery to replace a damaged or absent meniscus in the knee with a donor meniscus (allograft), although the technique of using a tendon from the patient's knee (autograft) has been described. This procedure aims to restore knee function, relieve pain, and prevent further degeneration of the joint, especially in young and active patients.

Candidates typically present with chronic knee pain, swelling, and mechanical symptoms such as locking or stiffness that affect daily activities and athletic performance.

This procedure is recommended in young patients without advanced knee arthritis, as the presence of severe joint degeneration limits the success of transplantation.

Meniscal transplant surgery consists of several steps. First, extensive imaging studies (MRI, CT, and X-rays) are performed to evaluate the knee and ensure proper sizing and matching of the donor meniscus. The donor meniscus is carefully examined and prepared to match the anatomy of the recipient's knee.

During the procedure, which is performed arthroscopically, the remaining fragments of the original meniscus are removed and the articular surface is prepared for transplantation. The donor meniscus is placed and secured with sutures and anchors to ensure stable proper integration with the surrounding tissue. Alignment and fit are checked to reproduce the natural biomechanics of the knee.

When the knee presents an inadequate bony alignment, a corrective osteotomy is considered in the same intervention to improve the load axis and avoid joint wear. If there is a cartilage lesion and it meets the criteria for a repair procedure, it is also considered to be performed in the same surgery.

Patellofemoral instability occurs when the patella luxates (slips) or subluxates (partially luxates) from its normal position in the femoral groove. This may be due to anatomical abnormalities, ligamentous laxity, or trauma. It is more common in adolescent females and people who play sports that involve rapid changes in direction or have structural deviations of the knee.

Symptoms of patellofemoral instability include displacement of the kneecap out of place, sharp pain in the front of the knee, swelling, and difficulty performing activities that involve bending or straightening the knee. Patients may also feel the knee give way, especially during physical activities, and a feeling of tightness or instability that can limit mobility and athletic performance.

The surgical options for patellofemoral instability are primary repair and reconstruction to restore stability and prevent the problem from persisting.

Primary repair is performed in acute injuries with minimal soft tissue damage. It consists of making a small wound on the inside of the patella to suture the torn medial femoropatellar ligament (MPFL) in its anatomical position using sutures and anchors, thus stabilizing the patella and ensuring its proper movement in the femoral groove.

Reconstruction is preferred when chronic instability, major anatomical abnormalities, or extensive ligamentous injury occurs. The procedure consists of reconstructing the MPFL using one's tendon (autograft) or from a donor (allograft). During the procedure, the graft is carefully placed and fixed to the patella and femur to mimic the normal insertion of the ligament and provide stability.

If there is a significant bony component contributing to instability, such as trochlear dysplasia or high patella, additional procedures such as trochleoplasty or tibial tubercle transfer may be performed to treat these underlying problems. Generally, these on-bone techniques are left for cases of severe bony deformity or in cases of failure of repair or reconstruction techniques.

Knee cartilage injuries affect the smooth tissue that lines the ends of the bones within the joint. This tissue is avascular, meaning it has no direct blood supply, making natural healing difficult. Damaged cartilage can cause pain, decreased function, and general knee instability.

Injuries can be caused by acute trauma, repetitive strain, and degenerative conditions, even in adolescence.

Symptoms of cartilage injuries are persistent knee pain, especially with weight bearing, swelling, stiffness, and loss of range of motion. Patients may also experience mechanical symptoms such as clicking, locking, or catching in the joint. If left untreated, these injuries can progress to osteoarthritis and greatly affect the patient's quality of life.

Advanced surgical techniques are available to treat cartilage lesions that, although large, do not affect enough of the joint to be considered established osteoarthritis. Two of these are minced cartilage and osteochondral autograft transplantation (OATS), also known as mosaicplasty.

Minced cartilage is a novel technique that involves taking small pieces of healthy cartilage from the patient and transplanting them to the area of injury. The procedure begins with an arthroscopic examination to assess the extent of cartilage damage. Healthy cartilage is removed from the edges of the defect and, if insufficient, from a non-weight-bearing, non-marring area of the joint. Upon removal, it is finely cut and mixed with a biological scaffold of platelet-rich plasma (PRP) that promotes cell adhesion and growth. This mixture is applied to the area of injury to create an environment conducive to cartilage regeneration and healing. Minced cartilage has many advantages, including minimally invasive surgery, shorter recovery time, and natural tissue regeneration. The biological scaffold promotes the integration and growth of new cartilage cells.

Mosaicplasty is based on transferring osteochondral grafts (bone and cartilage) from non-weight-bearing areas of the knee to the damaged area. These grafts have both cartilage and underlying bone, so it is a robust and immediate restoration of the articular surface, very effective when the injury affects not only the cartilage but also the bone. The procedure consists of extracting one or more cylinders from no-load or low-load donor areas of the knee and implanting them in the defect area. In this way, the transplanted cartilage matches the surrounding tissue in composition and function, making the repair more natural and effective.

Both techniques seek to improve joint function and relieve pain, avoiding or at least delaying the onset of osteoarthritis and the need to consider joint replacement surgery (prosthesis).

Misalignment of the knee (varus, valgus, and tibial slope) affects joint mechanics, causing uneven weight distribution and stress on specific parts of the knee. This can be due to congenital causes, previous injuries, or degenerative changes, and can lead to osteoarthritis.

Patients with knee misalignment present with pain, especially on the more weight-bearing side, swelling, stiffness, and decreased range of motion. Over time, this malalignment can accelerate cartilage wear, degenerate the joint, and impair overall knee function, severely affecting the patient's quality of life.

Knee osteotomy is a surgical procedure to correct malalignment and symptoms by realigning the knee joint. This involves cutting and reshaping the tibia (high tibial osteotomy, or HTO) or femur (distal femoral osteotomy, or DFO) to redistribute mechanical forces across the knee, reducing stress on the damaged compartment and preserving healthier cartilage. In cases of very severe deformity, both femoral and tibial osteotomies are performed.

During osteotomy surgery, one or more cuts are made creating a wedge-shaped opening. The angle and size of the wedge are determined before surgery based on imaging and planning to achieve the desired correction. The bone is then realigned and the gap is either closed (closing wedge osteotomy) or opened (opening wedge osteotomy) depending on the specific correction required. The realigned bone is stabilized with plates and screws or metal staples to ensure adequate healing and structural integrity.

Patella (kneecap) and proximal tibial plateau fractures are serious knee injuries that occur from high-impact trauma such as falls, car accidents, or sports-related injuries. These fractures compromise knee stability and function and require prompt and accurate medical attention.

The patella is a pulley that allows for proper knee extension. Symptoms of patella fracture are sharp pain in the front of the knee, swelling, bruising, and inability to actively extend the leg or bear weight. There may be a palpable gap if the fracture is displaced. Surgical options for these injuries depend on the severity and displacement of the fracture. For nondisplaced or minimally displaced fractures, conservative treatment with immobilization in a cast or brace may be sufficient. However, displaced fractures usually require surgery. Open reduction and internal fixation (RAFI) is a common procedure in which bone fragments are repositioned and stabilized with screws, wires, or plates to ensure proper alignment and healing. If the patellofemoral ligaments are injured during the fracture, they are repaired using suture anchors.

Fractures of the proximal tibial plateau occur in the upper part of the tibia and affect the bearing surface of the knee joint. These fractures are associated with severe pain, swelling, and limited range of motion. There may be visible deformity and instability, especially if the fracture is severe or has multiple fragments. Fractures of the proximal tibial plateau usually require surgery as they affect knee function and alignment. Depending on the area and degree of joint and bone involvement, percutaneous (minimally invasive) fixation with two or three screws assisted by arthroscopy or open reduction and internal fixation with one or more plates through one or more wounds may be performed. In high-energy fractures, a temporary external fixator is usually placed until the tissue has deflated and definitive surgery can be performed. In cases of severe injuries, a definitive external fixator may even be considered, which will remain in place until the injury has healed.