The anterior cruciate ligament (ACL) is one of the four major ligaments of the knee. Ligaments are strong, dense structures made of connective tissues that help stabilize a joint. In this case, the ACL connects the femur to the tibia and helps provide stability to the knee and minimize stress across the knee joint. Twisting or pivoting movements can often cause the ACL to strain or tear.
ACL tears occur in athletes participating in cutting and pivoting sports such as basketball, football, soccer, and skiing. At the time of an ACL injury the athlete typically feels a “pop” or a tearing sensation. This is followed by swelling within the first six hours of the injury. The most common injury associated with ACL tears is a meniscus tear.
It is well recognized that ACL injuries are much more common in females. There are multiple reasons for this including bone anatomy, hormonal differences, muscular balance, and the way they perform certain sports. Of these factors, the ones we can potentially change are muscular balance and the way sporting moves are completed. Females tend to cut and jump with their knees only slightly bent, which can predispose them to ACL injury. The hamstring to quadriceps strength ratio is also different from males. Studies have shown that strengthening exercises and plyometric programs aimed at changing these factors can prevent ACL injuries.
ACL strains can sometimes be treated with physical therapy and muscle strengthening. However, most complete tears require surgery in active patients. Modern ACL surgery involves completely removing the torn ligament and reconstructing the torn ACL. The most common grafts used to reconstruct a torn ACL are the patella tendon, hamstring tendons, or cadaver tissue (allograft). Each graft offers specific advantages and disadvantages, so it is important to understand the differences.
The meniscus is a pad of specialized cartilage that is located between the femur and tibia bones in the knee joint. There are two menisci in the knee – one on the inside of the knee (medial meniscus) and one on the outside of the knee (lateral meniscus). The meniscus has several functions including: acting as a shock absorber or cushion, distributing load across the knee, decreasing friction, and adding to stability of the knee.
Meniscus tears typically occur as a result of twisting injuries to the knee. They can be caused by traumatic injury, often seen in athletes, or they can be degenerative in nature, tearing from minor trauma as the meniscus becomes more brittle with age. The symptoms of a meniscus tear include pain, swelling, locking, and inability to completely straighten the knee joint. An MRI is frequently obtained to diagnose a meniscus tear.
Treatment of meniscal tears depends on several factors including the type of tear, the location of the tear, and the activity level of the patient. Some patients can be treated nonoperatively. If surgery is necessary, minimally invasive arthroscopic techniques are used to either trim out the torn portion of the meniscus (partial meniscectomy) or to repair the meniscus.
Cartilage is a type of specialized connective tissue. There are three main types of cartilage: hyaline (articular) cartilage, fibrocartilage, and elastic cartilage. Hyaline (articular) cartilage provides a smooth, white, glistening layer covering the femur, tibia, and undersurface of the patella. The main functions of the hyaline cartilage is to provide shock-absorbing properties and allow for a frictionless smooth surface. Articular cartilage lacks blood supply and therefore has a limited capacity for healing. It can be injured by trauma or repetitive injury.
Cartilage injuries may cause pain, swelling, and/or locking if the fragment has separated into the joint. The surgical treatment options for cartilage damage are: debridement (cleanup), microfracture, cartilage (osteochondral) transplant, allograft, and chondrocyte transplantation. These cartilage restoration procedures can be done using minimally invasive arthroscopic techniques.Microfracture
The microfracture technique is used for full thickness cartilage defects with exposed bone. Articular cartilage has a limited capacity to regenerate itself due to its lack of blood supply. Therefore, the microfracture technique was designed to stimulate a biologic repair for this type of cartilage. A minimally invasive arthroscopic technique is used to place microfracture holes into the exposed bone, which allows the release of blood and bone marrow contents into the cartilage defect. This activates a healing response and stimulates the production of the fibrocartilage layer, which forms over the exposed bone. This technique is very effective for cartilage restoration.Transplant (OATS)
Osteochondral (cartilage) transplantation (OATS) procedures are designed for full thickness chondral defects. Small chondral defects are treated by removing an osteochondral cylinder (plug) from a specific area within the knee joint that does not require cartilage to function properly. This osteochondral cylinder (plug) is then transplanted to the affected area in order to repair the chondral defect.
Large chondral defects can be treated using an allograft (cadaver) osteochondral graft. The typical patient considered for this procedure is a young, active individual with a traumatic isolated chondral injury. The advantage of this procedure is that it allows placement of hyaline (articular) cartilage into the chondral defect. This technique is performed through a minimally invasive arthroscopic procedure, or through an open technique depending on the size and location of the lesion.Allograft
Some cartilage lesions are too large for microfracture or autograft OATS to work successfully. Thus, an allograft OATS surgery may be required in some of these cases. In this surgery a cylindrical area of bone is removed where the cartilage lesion is located. A similar sized bone plug with overlying articular cartilage is then removed from a matched cadaver. This cylindrical area of bone is then placed in the defected area in order to repair the cartilage lesion.Chondrocyte Transplantation
Chondrocyte transplantation is used for relatively large cartilage defects in the knee, where the underlying bone is normal. This procedure is usually done in one of two ways. Cartilage cells can be harvested from the patient, sent to a lab, grown, and then later implanted into the patient via a second surgery. The other option is to use fetal chondrocyte cells, which requires only one surgery. In either case the lesion is cleaned of any residual cartilage. A tissue patch is then sewn into the lesion and cartilage cells are injected into the area. These cells then grow into hyaline (articular) cartilage.
Knee injury extremely common
History will direct the examination and helpwith diagnosis
Physical examination directed to the history– Keep in mind the rules of thumb
Treat based on the injury and also the patient
Most knee injuries can be treated withoutsurgery
– Need to rehabilitate the athlete