Definition: A knee sprain means that you have injured one of the ligaments around the knee joint. Saying you have a “knee sprain” is not a terribly useful diagnosis for two reasons: irst: it does not tell you which ligament is injured. This is important because different ligaments are treated very differently. For example, ACL (anterior cruciate ligament) injuries often need surgical reconstruction. On the other hand MCL (medial collateral ligament) injuries seldom require surgery. Second: it does not tell you how badly the ligament is injured. The reason this is important is that minor injuries usually require minor treatment. More severe injuries may require more substantial treatment, rehabilitation, and possibly surgery. Despite this, patients are often told they have a knee sprain. If you are diagnosed with a knee sprain, try to get more information. Find out which ligaments are injured, and then you will be able to understand more about what possible treatments and rehabilitation are necessary.
The anterior cruciate ligament or ACL, is one of four major knee ligaments. The ACL is critical to knee stability, and people who injure their ACL often complain of symptoms of their knee giving-out from under them. Therefore, many patients who sustain an ACL tear opt to have surgical treatment of this injury. An ACL tear is most often a sports-related injury. ACL tears can also occur during rough play, mover vehicle collisions, falls, and work-related injuries. About 80% of sports-related ACL tears are “non-contact” injuries. This means that the injury occurs without the contact of another athlete, such as a tackle in football. Most often ACL tears occur when pivoting or landing from a jump. The knee gives-out from under the athlete when the ACL is torn.
Female athletes are known to have a higher risk of injuring their anterior cruciate ligament, or ACL, while participating in competitive sports.
The posterior cruciate ligament or PCL is one of four ligaments important to the stability of the knee joint. The anterior cruciate ligament, or ACL, sits just in front of the PCL. The ACL is much better known, in part because injuries to the ACL are much more commonly diagnosed than injuries to the PCL. Interestingly, it is thought that PCL injuries account for about 20 of knee ligament injuries, however, the PCL is seldom talked about because these injuries are often left undiagnosed. The PCL is the ligament that prevents the tibia (shin bone) from sliding too far backwards. Along with the ACL which keeps the tibia from sliding too far forward, the PCL helps to maintain the tibia in position below the femur (thigh bone).
How is the PCL injured?
The most common mechanism of injury of the PCL is the so-called “dashboard injury.” This occurs when the knee is bent, and an object forcefully strikes the shin backwards. It is called a ‘dashboard injury’ because this can be seen in car collisions when the shin forcefully strikes the dashboard. The other common mechanism of injury is a sports injury when an athlete falls on the front of their knee. In this injury, the knee is hyperflexed (bent all the way back), with the foot held pointing downwards. These types of injuries stress the PCL, and if the force is high enough, a PCL tear will result.
What are the symptoms of a PCL injury?
The most common symptoms of a PCL tear are quite similar to the symptoms of an ACL tear. Knee pain, swelling, and decreased motion are common with both injuries. Patients may have a sensation that their knee “popped” or gave out. Problems with Knee instability in the weeks and months following PCL injury are not as common as instability following an ACL tear. When patients have instability after a PCL injury they usually state that they can’t “trust” their knee, or that it feels as though the knee may give out. If this complaint of instability is a problem after a PCL injury, it may be an indicator that surgery is recommended.
There are two menisci in your knee; each rests between the thigh bone (femur) and shin bone (tibia). The menisci are made of tough cartilage and conform to the surfaces of the bones upon which they rest. One meniscus is on the inside of your knee; this is the medial meniscus. The other meniscus rests on the outside of your knee, the lateral meniscus. These meniscus functions to distribute your body weight across the knee joint. Without the meniscus present, the weight of your body would be unevenly applied to the bones in your legs (the femur and tibia). This uneven weight distribution would cause excessive forces in specific areas of bone leading to early arthritis of knee joint. Therefore, the function of the meniscus is critical to the health of your knee. The meniscus is C-shaped and has a wedged profile. The wedged profile helps maintain the stability of the joint by keeping the rounded femur surface from sliding off the flat tibial surface. The meniscus is nourished by small blood vessels, but the meniscus also has a large area in the center of that has no direct blood supply (avascular). This presents a problem when there is an injury to the meniscus as the avascular areas tend not to heal. Without the essential nutrients supplied by blood vessels, healing cannot take place.
How does the meniscus work?
The knee joint is very important in allowing people to go about performing almost any activity. The joint is made up of three bones: the femur (thigh bone), the tibia (shin bone), and the patella (knee cap). The surfaces of these bones within the joint are covered with a layer of cartilage. This important surface allows the bones to smoothly glide against each other without causing damage to the bone. The meniscus sits between the cartilage surfaces of the bone to distribute weight and to improve the stability of the joint.
Meniscus Tear or Cartilage Tear?
Both the covering of the bone within the joint and the meniscus are made of cartilage–this makes the issue a little confusing. People often say ‘cartilage’ to mean the meniscus (the wedges of cartilage between the bone) or to mean the joint surface (so-called articular cartilage which caps the ends of the bone). When people talk about a cartilage tear, they a talking about a meniscus tear. When people talk about arthritis and wear of cartilage, they are talking most often about the articular cartilage on the ends of the bone.
What happens with a meniscus tear (torn cartilage)?
The two most common causes of a meniscus tear are due to traumatic injury (often seen in athletes) and degenerative processes (seen in older patients who have more brittle cartilage). The most common mechanism of a traumatic meniscus tear occurs when the knee joint is bent and the knee is then twisted. It is not uncommon for the meniscus tear to occur along with injuries to the anterior cruciate ligament (ACL) and the medial collateral ligament (MCL)-these three problems occurring together are known as the “unhappy triad” which is seen in sports such as football when the player is hit on the outside of the knee.
Symptoms of a Meniscus Tear?
Individuals who experience a meniscus tear usually experience pain and swelling as their primary symptoms. Another common complaint is joint locking, or the inability to completely straighten the joint. This is due to a piece of the torn cartilage physically impinging the joint mechanism of the knee.
The most common symptoms of a meniscus tear are:
Knee pain, swelling of the knee, tenderness while palpating the meniscus, poping or clicking within knee, and limited range of motion.
Patello-femoral pain (PFP) is the most common knee disorder. It is particularly common among adolescent girls and active individuals. The patient commonly presents with anterior knee pain that worsens with stairs, prolonged sitting/flexion, and kneeling or squatting activities. Common complaints are pain when attempting to rise after sitting and watching a movie or after a long drive. The patient may also experience swelling after activities and may complain of a “popping” sensation with ambulation.
The patella functions to aid in knee extension by acting as a pulley system to increase the angle of the moment arm of the quad tendon. Normally, as the knee flexes from 25-130° and the patella moves along the trochlear groove, it tilts medially approximately 11° and laterally rotates 6-7°. If normal patellar motion is restricted or excessive, the patella can translate out of its groove and degeneration of the patellar facets can occur. This can lead to significant pain and dysfunction. Predisposing factors that can lead to alteration in normal patello-femoral movement can include the following: trauma, osteochondritis dissecans, malalignment, tightness of the hamstring, IT band or lateral retinacula, external tibial torsion, weakness or delayed firing of the VMO, and increased Q angle.
Various conservative measures can and should be taken when addressing PFP including exercise for stretching and strengthening, bracing, taping, and orthotics. All should be considered when evaluating the patient and issuing treatment. If exercise is prescribed, the primary focus should be on quad retraining and strengthening. Biofeedback and muscle stim are helpful tools to regain neuro-muscular quad control. VMO activity is critical due to its angle of insertion and resultant pull on the patella. Studies utilizing normalized EMG values have shown that no specific exercises can be utilized to preferentially recruit the VMO over other parts of the quad. Because of this, a generalized quad strengthening program is in order.
The therapist needs to be aware of the knee angles that increase joint reaction forces on the PF joint. For closed kinetic chain activities such as the leg press, maximum joint reaction forces occur when contact between the patello-femoral surfaces is the greatest (60-90°). On the other hand, maximum joint reaction forces during open kinetic chain activities such as knee extension occur when contact between patello-femoral surfaces is the least (30-0°). With increased knee flexion, there is a concomitant increase in contact area between the patella and femur. This is important because the increased contact area serves to disperse the forces on the PF joint. On the other hand, even though contact forces are less at smaller flexion angles, the contact area is also less. Because of this, patients with degeneration at the articular surface will probably experience pain with open kinetic chain knee extensions from 30-0°. It is important to differentiate between PF instability and PF arthritis in order to give the proper exercise prescription. Patients with PF degeneration will have pain with deep knee flexion closed chain activities whereas patients with instability will typically have pain at end range extension. Both groups should perform exercises in a pain-free range but this range will differ based on the diagnoses. Patients with PF arthritis may only be able to tolerate closed chain activities from 0-45°. On the other hand, those with instability need to exercise in deeper ranges of flexion (>30°) where the femoral condyles help to stabilize the patella.