A knee sprain occurs when the ligament(s) of the knee sustains damage. Sprains result from sports and recreational activities, direct knee contact, or falls. Knee trauma is particularly common in young athletes.
The patient history for a knee sprain, especially that of an ACL tear, is positive for a popping sensation at the time the injury was sustained. Another pertinent detail is the timing and amount of joint effusion. If the effusion is large and develops within two hours, this is indicative of an ACL rupture. However, a smaller amount of effusion that occurs within 24 to 36 hours is suggestive of a sprained ligament. Patients describe pain and instability as well as the inability to engage in physical activities.
On physical examination, the knee displays mild edema, localized pain and tenderness, and good stability. Additionally, the ligament demonstrates a solid "end-point," which is a set limit during a stretch test,
This presents with moderately localized pain and tenderness as well as mild instability. The exam reveals the presence of an end-point.
This type of sprain features edema, pain and tenderness, complete instability, and the absence of an end-point which may be limited by tenderness on exam. Additionally, patients are unable to ambulate.
When a patient presents with an injury suspicious for a sprain, the clinician should ascertain key details such as whether there was direct contact. Other important aspects of the history include whether the knee twisted, hyperextended, decelerated, suddenly stopped, and if the foot was planted on the ground during the mechanism that caused the sprain.
In addition to obtaining the above history, a thorough physical examination is vital. Initially, the clinician will observe the patient's gait, the positioning of the affected knee, any possible asymmetry, presence of hemarthrosis, and the development of effusion. The latter is suggested by the absence of peripatellar groove.
This is followed by an extensive stress test to evaluate the ligaments and to differentiate between partial and complete tears. There are numerous maneuvers to test for individual ligaments. The results help guide the clinician's diagnosis. For example, the Apley, anterior drawer, and posterior drawer techniques will test the integrity of particular ligaments, If pain or swelling limits the exam, then radiographs should be performed prior to physical testing. Analgesics may be used to allow the clinician to examine the patient.
Another component that should be assessed is the vascular status. Therefore the leg pulses and the ankle-brachial blood pressure index should be obtained.
As an initial imaging tool, radiograph series of the knee can be performed to determine if there are fractures, misalignment, maturity, and any present pathology. The main x-ray views are anterior-posterior, lateral, tunnel, and sunrise.
According to the Ottawa knee rules, x-rays are required if 1) patient is older than 55 years of age, 2) there is tenderness in the patella (but not the other bones in the knee, 3) there is tenderness of the head of the fibula, 4) patient cannot flex the knee by 90°, and 5) patient is unable to bear weight on the affected knee immediately after sustaining the injury and in the emergency department through four steps.
MRI may be performed for the analysis of soft tissue damage. In addition to evaluating ligamentous tears, this modality also reveals meniscal tears and bone contusions. However, MRI is not useful for grading and it may underestimate the severity of the damage .
The therapeutic approach generally depends on the degree of the knee sprain. First and second-degree sprains are treated similarly in a conservative matter while grade 3 injuries are more complicated and may warrant surgery.
The main therapy consists of four components which are to protect, rest, ice, elevate and compress the knee in order to treat the pain, swelling, and bruising. Patients may take nonsteroidal anti-inflammatory drugs (NSAIDs) as well.
The recommendations for patients with grade 1 sprains enables them to participate in activities as tolerated. They may use crutches to protect the knee from weight bearing. Once the pain is tolerated, the patient may begin mobility and muscle strengthening exercises. Furthermore, exercises that place them at high risk for further damage such as tackle sports are generally restricted. The ligament takes 3 to 6 weeks to heal.
In addition to PRICE and the use of NSAIDs, an individual with grade 2 sprains should protect the knee with a brace during heavy activities. Patients should be subscribing to physical therapy and performing exercises to strengthen the muscles and help the knee joint achieve balance and stability.
Patients with grade 2 injuries are advised to restrict activity for 6 weeks.
Third-grade sprains are often extensive and commonly involve other structures. The knee should be splinted or placed in a knee immobilizer. Moreover, these patients are referred to an orthopedic surgeon who will assess the need for surgical intervention. The latter depends on the extent of the ligament tear, the number of affected ligaments, the degree of instability, other involved structures, and whether there is an increased risk of knee trauma in the absence of surgery. In a repair or reconstruction, the torn ligament is replaced with a tendon graft.
Following surgery, the patient will engage in an extensive rehabilitation program, especially if s/he must resume a high level of activity.
Generally, individuals with a sprain achieve full recovery with proper management. Grade 1 and 2 sprains heal after physical therapy and activity restriction. Moreover, third-grade ligament sprains accompanied by other ligament or meniscal injuries will typically require surgery followed by intense rehabilitation. These are expected to heal but take longer than milder sprains.
There are numerous causes of a knee sprain. Sports such as football, soccer, basketball, gymnastics, hockey and skiing commonly produce this injury.
Damage to the knee can occur as a consequence of direct contact. Moreover, abnormal movements that destabilize the knee are prone to causing sprains. For example, planting the foot on the ground followed by rapidly twisting of the knee is risky. Additional scenarios include running and then stopping, or running and then suddenly changing direction. Also, jumping and then landing such as in gymnastics, falling onto a bent knee, or hyperextension of the knee are all causes of sprains.
With regards to specific etiologies, approximately 30% of anterior cruciate ligaments (ACL) injuries occur due to contact  and the remaining cases are the result of leg deceleration in the setting of a contacted quadriceps muscle and an extended knee .
There are intrinsic factors that contribute to the likelihood of knee sprains such as the body habitus, shape of the foot, dominance and laxity of the legs and ligaments. The strength of the hamstring muscle  as well as the dominance of the quadriceps can contribute to the development of these knee injuries .
A 10-year study that followed 6.6 million knee injuries in emergency departments throughout the United States reported an annual incidence of 2.3 knee injuries per population of 1,000. Strains and sprains accounted for 42% of the knee traumas . Furthermore, there are an estimated 2.5 million sports-related knee injuries yearly among adolescents.
With regards to patient demographics, the age group with the highest rate, 3.83, is observed in those ranging from 15 to 24 years. The lowest rate, 0.5, is exhibited by children under 5 years . This study also demonstrated differences in age. For example, sports activities accounted for most injuries in the youth while elderly patients sustained sprains due to stairs, ramps, and floors .
Overall, researchers discovered that sports and recreational tasks were responsible for 49% of injuries while 45% were caused by home structures and furnishings .
Another study investigating injuries in high school students revealed that knee traumas emerged most commonly from football, girls' soccer, and girls' gymnastics, respectively, among adolescent athletes . Furthermore, it corroborated that the medial collateral ligament (MCL) is the most commonly injured structure in adolescent athletes (36%), while ACL was the second most frequent (25%) .
The knee is a complex structure. There are numerous extracapsular structures that contribute to the stabilization of the knee. The hamstring and quadriceps muscles, the muscle insertions, and extracapsular ligaments such as the lateral collateral ligament (LCL) together strengthen the joint externally. Intracapsular stabilizers include the capsule itself, ACL and posterior cruciate ligament (PCL), and the menisci. These strengthen the joint internally.
Hence, the knee joint is vulnerable to injuries since it depends on its ligaments and muscles for stability. Direct contact can be harmful. Additionally, sudden muscle contraction in situations where one is running and then switching direction can cause trauma to the ligaments.
Knee sprains are classified in accordance with their severity.
Patients with a grade 1 sprain have mild damage to the ligament, which was slightly stretched to a small degree. It still provides stability to the knee joint.
This type of sprain is often characterized by a partial tear of the ligament, which leads to a weakening of the joint and mild instability. Other knee structures are commonly involved.
A third-degree sprain is typified by a complete tear or disruption of the ligament. There is excessive knee instability as other knee structures are very likely to be affected as well.
With regards to associated injuries, at least 60% of cases with ACL tears are accompanied by meniscal damage while 46% have collateral ligament involvement .
There are recommendations for the prevention of knee injuries. For example, individuals should avoid playing on wet ground and in risky weather conditions such as rain or snow if possible. It is also important for athletes and all others to wear the correct and appropriate footwear.
Also, individuals should carefully choose the appropriate physical exercises that suit their overall current health status. They should seek their clinician's advice regarding what is best.
On another note, specific physical regimens can reduce the risk of obtaining knee sprains. One study implemented a neuromuscular training program involving stretching, strengthening, plyometrics, and agility activities to successfully reduce ACL injuries . Hence, it is important to incorporate such safe exercises.
A knee sprain results from an injury to a ligament and is characterized by tears in the ligamentous fibers. The damage may be sustained during various abnormal movements stemming from sporting or recreational activities, home projects, other physical tasks. Knee traumas are among the most frequently occurring sports-related injuries , especially in young athletes. A sprain may involve more than just a ligament as other structures may be involved, especially in higher degree sprains.
The clinical picture of a sprain consists of pain, instability, swelling and/or hemarthrosis. The sprain is graded on the degree of severity as assessed by physical exam. The instability in grade 1 sprains is mild whereas it is severe in grade 3.
The diagnosis is determined primarily through a complete history and a knee exam. The physician should obtain a detailed account of how the injury was sustained while taking note of the gait and symmetry of the knees. Specific physical maneuvers will identify damaged ligament(s) and other associated structure(s) if present. Radiographs are not always required but there are guidelines regarding which patients should undergo imaging. Also, some patients may need further testing with magnetic resonance imaging (MRI).
The treatment for grade 1 and 2 sprains is similar. The knee requires protection with a brace, rest, ice, compression, and elevation (PRICE). Grade 3 often requires surgical intervention for repair and/or reconstruction, especially since other structures may be damaged as well. Physical therapy and rehabilitation are important for all sprains. Patients with proper treatment of sprains are expected to attain full recovery.
Prevention of sprains involves strategies such as wearing proper footwear, avoiding wet weather and risky conditions during sports and recreational activities, and participating in exercise regimens that focus on strengthening the muscles.
What is a knee sprain?
The knee joint is a complex structure. It relies on structures both inside and outside the knee for stability. Specifically, the ligaments, which are strong fibers, keep the knee in one place. The collateral ligaments, known as medial collateral ligament (MCL) and lateral collateral ligament (LCL) are located on both sides of the knee to prevent it from moving to either side. The cruciate ligaments are known as anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) prevent the knee from moving forward or backward. The most common sprains involve the MCL and ACL.
A knee sprain develops when there is a tear in the ligament(s).
What are the causes?
Abnormal movements such as the following can cause a knee sprain:
Sports such as the following commonly produce sprains:
What are the signs and symptoms?
The following are symptoms of knee sprains:
How is it diagnosed?
During the assessment, the clinician will ask the key questions about how the patient sustained the injury and all the symptoms. The clinician will also observe how the patient is walking, how the knees are positioned, and how the patient is positioned during the exam. The next component of the assessment is the physical exam itself with stress testing movements that help guide the doctor to identify the involved ligament(s). If there is great pain, then, pain medications may be given prior to the exam. Also, x-rays may be obtained to rule out fractures. Sometimes, an MRI test is also obtained.
How is it treated?
In mild and moderate sprains:
In severe sprains:
How can it be prevented?
What is the prognosis?
Generally, knee sprains recover and heal well with physical therapy and activity restrictions. Mild to moderate sprains can take up to 6 weeks to heal. Severe sprains often require surgery to be followed by extensive rehabilitation.