Knee Injuries


Knee Injuries

Ron Noy, MD

Knee injuries are among the most common injuries in athletes of all ages. They have become more prevalent for many reasons, including participation in high-risk sports at an earlier age, particularly by females; increased participation in sports by those over 50 years of age; popularization of high-risk activities such as obstacle course races and extreme lifting or exercise programs; and more frequent participation during the week.

Because of social media and other online sources of information, there is more awareness of different types of injuries, giving the opportunity for earlier intervention. Continuing advances in diagnostic evaluation and tests combined with improved treatment options help today’s athletes at all levels get back to normal life and sports while preventing long-term disabilities.




Patellofemoral Syndrome


Iliotibial Band Syndrome


Meniscal Tear


Medial Collateral Ligament Tear


Anterior Cruciate Ligament Tear


Posterior Cruciate Ligament Tear


Lateral Collateral Ligament Tear


Patellar Tendinitis


Patella Fracture


Patellofemoral Instability


Osgood-Schlatter’s Syndrome


Osteochondritis Dissecans



Common Causes

Patellofemoral syndrome, also known as chondromalacia patella, is the most common cause of anterior knee pain without a traumatic event. While more common in women, it is prevalent in all genders and age groups. Sports that require impact (running and jumping), repetitive bending (baseball or softball catcher, weightlifting, golf), sitting (rowing, race car driving, gaming), and climbing (hiking, obstacle courses) can cause this problem over time and are most likely to cause flare-up of symptoms. Direct trauma to the kneecap (patella) also leads to this problem, because it can injure the cartilage surfaces on the patella and femoral groove; but the symptoms are more likely to occur after prolonged sitting, repetitive stair climbing (down or up), running, or jumping.


Athletes will complain of vague pain in the front of the knee, often circulating their whole hand around the entire anterior knee when asked to locate the pain. However, it is also common for the pain to radiate medially, posteriorly, or, less commonly, laterally, which often confuses patients when researching their symptoms on the Internet. While buckling is more common with other injuries like anterior cruciate ligament (ACL) and meniscus tears, it is not uncommon to have this occur after prolonged sitting and then suddenly climbing up or down stairs, such as on a long commute on a subway or train followed by needing to exit up a long flight of stairs. Swelling is usually mild and not perceived by the athlete, but rather described as soreness the next day. The joint effusion rarely is great enough to restrict flexion or stop the athlete from participating in sport but is enough to cause the quadriceps muscle to become weaker. It is the body’s way of trying to get the athlete to stop performing the activity. Weak quadriceps allow less control of the kneecap during motion, which in turn causes more swelling, which then causes more weakness and thus perpetuates the symptoms and prolongs recovery.

Positive findings on physical examination include results from the “grind test.” This is performed by pressing posteriorly and distally on the quadriceps at rest, and then having the athlete fire the quadriceps by pressing the thigh down into the exam table, which will cause sharp pain. Crepitus, or a crunching feel during flexion and extension, is another positive sign, but is not always present. Sometimes people may actually hear crackling when bending or even walking, which indicates more advanced surface cartilage degradation. Tenderness can be present along the anteromedial joint line, but this can also be related to another entity, a plica. A plica is a normal infolding of the capsular tissue sometimes present in the knee joint. On occasion, primarily in runners, it can get entrapped between the patella and femoral condyle. When this happens, it gets inflamed and acutely painful until the inflammation subsides. Patients with this problem added to patellofemoral syndrome may describe a “rubber band” feeling during bending. The band can thicken as well over time and start to further erode the cartilage on the patella or femoral condyle.

Athletes with higher Q angles (the angle formed by the quadriceps and patella tendon) are more susceptible to lateral compression and wear in this area. Q angles tend to be higher in females due to normal anatomical variants in the hip, femur, and tibia, but rarely need surgical correction. AP (front to back) X-ray evaluation can show alignment issues, while lateral (side) views can show a high (alta) or low (baja) patella. Both can lead to patellofemoral pain, but only patella alta is associated with patella instability (see section on patella instability).

Skyline or merchant views (axial cross section) can also show lateral compression, tilt, and subluxation, all of which can be associated with this syndrome. Modern magnetic resonance imaging (MRI) techniques can show precise areas of damaged articular surface, tilt, subluxation, and plica, but are rarely necessary to make the diagnosis or initiate a treatment plan.


Most of the time, patellofemoral syndrome will improve with nonoperative treatment over six to eight weeks. The initial treatment consists of low-impact quadriceps and hamstring strengthening exercises. Therapy programs also focus on increasing flexibility, in addition to strengthening the thigh muscles. Medication is rarely needed, but nonsteroidal anti-inflammatory drugs (NSAIDs) may be used as an adjunctive treatment to reduce inflammation that can occur with this syndrome. Chondroitin sulfate with glucosamine can also be effective. Icing after exercise is important to prevent the inflammatory response, which can further cause quadriceps weakness until full strength is regained. A brace may be helpful but is not usually necessary.

Strengthening should include closed- and open-chain techniques, but repetitive flexion past 90 degrees should be avoided during any exercise. Lunges, while low impact, should also be avoided because this simulates going down stairs and puts too much stress on the kneecap.

If there is no improvement after four to eight weeks, an MRI scan should be added to see if there are cartilage fissures or flaps, inflamed thickened plica, OCD (osteochondral) lesions, or other possible causes of inflammation and pain that may be preventing successful treatments. Surgical treatment should then be considered for mechanical lesions (arthroscopy, osteotomy, tibial tubercle transposition, cartilage resurfacing, and even partial joint replacement), while injection therapies should be considered if there are no lesions. These can include cortisone (done less frequently now), hyaluronic acid (HA) viscosupplementation, PRP (platelet-rich plasma), BMA (bone marrow aspirate), fat stem cells, and birth product allograft stem cell injections.

Return to Action

Once athletes have regained full strength, they can return to sport. It often can take six to eight weeks for full recovery. Depending on the sport, some athletes may return earlier but may take longer for full recovery. Utilizing a brace or strap may allow participation prior to full recovery. Surgical patients will take much longer to return to sport, varying from 2 months with simple arthroscopies to 6 to 12 months with osteotomy and resurfacing surgeries.


Common Causes

The iliotibial band (ITB) can be irritated as it passes over the lateral side of the knee epicondyle at 30 degrees of knee flexion. Iliotibial band syndrome is an overuse injury, often experienced after running on hills or banked tracks. It is most commonly seen in long-distance runners and cyclists, particularly in triathletes who do both.


The pain is often described as radiating pain on the lateral side of the thigh anywhere from the lateral hip to the lateral knee and can be confused with radicular pain from the lower back at times. Pain onset occurs typically mid-run and can stop once running stops or linger on a bit afterward, but more advanced cases can cause constant pain. There is usually tightness to the ITB with a positive Ober test, as well as tenderness to the band itself. A positive thumb pressure test is pathognomonic. The examiner places a thumb on the lateral epicondyle of the knee’s distal femur while moving the knee through range of motion. If there is pain only when the knee is at 30 degrees of flexion, the test is positive. Swelling is rare and is more likely from an associated bursitis. Range of motion is not affected unless there is rare calcific tendinitis. X-rays will typically show some irritation response at the lateral epicondyle, but this is usually subtle and not diagnostic. Calcification at the lateral epicondyle is rare but associated with severe limiting pain. Magnetic resonance imaging scan is usually not necessary but may reveal an inflamed or thickened ITB.


Treatment initially consists of stretching the ITB and refraining from running and cycling. Stretches should include crossed-leg lateral lean to a wall to stretch the distal half of the ITB and figure four forward flexion to stretch the proximal half of the ITB, 30 seconds five times a day. A foam roller or rolling stick can be helpful when used properly. Formal physical therapy can be beneficial because the therapist can often stretch the athlete more effectively. Modalities such as ultrasound and electrical stimulation (e-stim) and manual therapy can help as well. Nonsteroidal anti-inflammatory drugs, pain creams, and ice are often used. Cortisone injection can help reduce inflammation in an adjacent bursitis, but should be avoided directly into the band itself because it can cause degeneration and tearing. Calcification, if present and persistently symptomatic, can be excised with minimally invasive techniques. Traditional surgery for recalcitrant cases has been described as removing an elliptical portion of the midsubstance of the part of the tendon that passes over the lateral epicondyle, but more recent techniques allow preservation of the ITB tendon by microdebridement of degenerative portions of the band only.

Cyclists should have their bikes evaluated and fitted properly. Runners should change to flatter or unbanked terrain to train. Shoe modification or orthotics or both can be helpful.

Return to Action

The athlete can return to sport once symptoms have resolved, but should continue a preventive stretching program. Commercially available ITB straps may allow earlier return during treatment. As always in repetitive sports like running and cycling, a slow and progressive return program is recommended.


Common Causes

The medial and lateral menisci are important structures in the knee. While the meniscus is often described as a shock absorber and “chock block,” the most important function is to share the load of the knee joint along a larger surface area. When you view the femoral condyles from the side, they are round whereas the tibia is predominantly flat. Without the meniscus, this would be like a tire on the road with the pressure at one point. The cartilage surface is not designed to withstand that much pressure and will eventually break down and become arthritic. The more intact the meniscus, the more area over which the load is distributed.

This is paramount when one thinks about how to treat meniscus tears, especially in adults, because the blood supply diminishes, reducing the capacity for healing a repair. The classic teaching dictates that 10 to 25 percent of the peripheral meniscus is vascular (red zone), with the majority of the remaining meniscus avascular (white zone); these divisions are more accurate in young children and adolescents. Most adults have only a small percentage of the periphery still vascular. It is the peripheral vascular zone that has greater chance for healing when compared to the inner, avascular zone.

Meniscus tears are more common in sports like basketball, football, soccer, snowboarding, skiing, and tennis, but can happen in any sport, especially if a slip or twist injury occurs. Medial meniscus tears are more common than lateral tears because more weight goes through the medial (inner) side of the knee, and the knee repetitively pivots more on the back portion of the medial joint. This causes degeneration in the posterior horn and mid one-third body of the medial meniscus, and a tear can occur with a sharp twisting injury quite easily. In younger athletes, the meniscus can tear as well even though the tissue is healthy, but it takes a bit more of a traumatic injury. Patients may describe a pop or even a crack as if they had broken a bone. Most often they can continue playing the game with some difficulty. They may experience delayed swelling overnight into the next day that is mild to moderate. The exception is a large peripheral tear through the vascular red zone, which can bleed and fill up the joint more quickly.

Types of meniscus tears include bucket handle, flap, parrot beaks, radial, cleave, and degenerative fraying.

A bucket handle tear of the meniscus can lock the knee (patient cannot flex or extend the knee) as the handle fragment of the tear flips and gets stuck in the front of the knee joint, capturing the condyle of the knee. In these cases, the athlete cannot put weight on the leg or move it, and is usually in significant discomfort. Degenerative meniscal tears can be minimally symptomatic or not symptomatic at all. If found incidentally on an MRI scan, they may not need to be addressed surgically at that time. If the tears are merely causing swelling after activity, a trial of physical therapy and injection therapy should be considered first. Other sources of symptoms should be identified and treated before resorting to arthroscopic surgery.

Mechanical symptoms such as frequent buckling or locking should be considered surgical cases, because buckling can cause more permanent damage to the articular surface as well as potentially increasing the size of the tear (the former is probably more likely). Since the goal is to preserve as much intact meniscus as possible, only the loose fragment should be removed during an arthroscopy and not the remaining stable degenerative area. Historically, these stable degenerative areas were removed as well in order to prevent future tears, but this rarely happens, and the more meniscus remaining the better.

Some experts suggest that removing meniscus tears causes arthritis, but it is actually the torn piece that is not sharing the load anymore that is the culprit, leading to the development of arthritis. Whether you remove this nonfunctional fragment or leave it in, the load is increased, which leads to arthritis. If the loose fragment is symptomatic and causes buckling, locking, pain on impact, or repetitive effusions that cannot be controlled with nonoperative management, it should be removed just as a loose body would be. The key is not to remove more meniscus than is absolutely necessary, and if there is a chance that repairing the meniscus will be successful, this should be attempted as well. Unfortunately, the retear rate in adults over 30 years of age is high. Adding biologics can to help improve these rates, but more research is needed.


Localized pain to the side of the meniscus and delayed mild swelling and discomfort after activities are the most common complaints. Athletes will most often continue playing through this for some time, and many team doctors will delay surgical intervention until the end of the season if possible. Buckling and locking suggest a larger tear with a loose fragment that may require surgery, and usually will get the athlete to seek attention sooner. Cutting and twisting are often painful. Pain at night during lying on the side is common for medial tears as the knees touch each other. There may be pain on stairs, but this can also happen with chondromalacia patella and is not pathognomonic.

The two hallmark tests used to identify meniscal tears are joint line tenderness and a positive McMurray test. The test is performed by twisting the knee while bending and extending it. Pain, clicking, or clunks are positive tests, suggesting that the meniscus tear may get caught in these positions and is unstable. The Appley test is rarely used by modern orthopedic surgeons, but historically was another test that could be utilized.

Medial meniscus tears are commonly associated with popliteal cysts, such as a Baker cyst. When the swelling in the knee gets great enough, the pressure can push the fluid though the meniscus, creating a cyst outside the joint (the wall of the cyst is capsular tissue that is distended; it’s like a bubble being blown with chewing gum). The fluid does not leak back into the joint, because the meniscus collapsed to create a one-way valve. Sometimes the cyst causes discomfort and can be the presenting symptom. These cysts most commonly occur through the degenerative oblique complex or cleavage tears. During surgery, theses cysts are decompressed as much as possible through the meniscus tears when there is still communication. The body will often wall off the communicating hole in the first week after surgery, which prevents recurrence, or the surgeon may close the hole during a repair.

Lateral meniscus tears can create cysts as well, but more often these are smaller ones called parameniscal cysts. They usually are not painful, but easily palpable as a hard structure like a marble on the lateral side of the knee. They usually are associated with radial tears through the mid one-third of the lateral meniscal body. During surgery, these cysts are decompressed from within the joint. As a radial tear may transect the meniscus into two halves, it is better to repair this tear and risk recurrence than to remove the tear, which would in turn detach the posterior and anterior horns from each other.

X-rays may show joint space narrowing in patients with degenerative meniscus tears. Some specialists can see tears on ultrasound, but the standard-of-care diagnostic imaging is an MRI scan, which is very accurate in confirming the diagnosis of a meniscal tear.


The vascular portion of the meniscus is in the peripheral portion and allows the best chance of repair to heal, especially for bucket handle types of tears. This area diminishes with age, but surgeons are pushing the limits in order to try to preserve as much meniscus tissue as possible for the reasons stated earlier. The addition of biologics may improve the ability to heal, but more studies are needed to determine this. The most common treatment is still a partial meniscectomy, removing the loose symptomatic portion of the tear. Nonoperative treatment certainly can be done if the meniscus tear is not symptomatic, which can occur when the tear is nondisplaced. If possible, surgery is delayed until after a sport season is over. The goal of surgery is to preserve as much functional meniscus as possible.

Return to Action

For nonoperative care, athletes can return when they do not experience buckling or locking episodes, because these can risk further damage to the knee. A pull-on knee sleeve can help performance.

For partial meniscectomy procedures, the athlete is weight bearing as tolerated with a cane immediately postoperatively. Once the athlete has full motion and strength, return to sport is allowed. This can be as early as two to three weeks in professional athletes, but usually takes four to six weeks.

Meniscus repairs require longer recoveries due to the time required to allow the repair to heal. These athletes are on crutches after surgery with restricted weight bearing and wear a brace that restricts motion past 90 degrees for four to six weeks to prevent stressing the repair site. Once the athlete has full motion and strength after the healing period is completed, gradual return to sport is allowed, monitored by swelling and pain. If either occurs, the program is adjusted. It often takes two months of slow progressive return to sport once playing begins again to reach preinjury performance levels.


Common Causes

The medial collateral ligament (MCL) is the extraarticular large thick ligament on the inner side of the knee, with superficial and deep components. Isolated injuries are most commonly from a valgus force to the knee, often from a blow by an opponent coming from the side with the foot planted. Noncontact injuries can also occur, while repetitive stress injuries are not common. Football offensive linemen are prone to these injuries due to the nature of their position, and some athletes use preventive braces. This injury is also common in skiing and soccer.


The athlete often recalls hearing or feeling a pop on the inside of the knee. The pain can be rather severe and make walking difficult. Significant relief during walking is seen with placement of a double upright hinged brace. There is tenderness along the MCL at the site of the tear, which can be felt proximally at the origin over the medial epicondyle of the femur, distal at the insertion on the tibia or at the midsubstance, or both. Proximal tears heal routinely whereas distal tears do not, possibly due to the disruption by synovial fluid.

Swelling on the medial side of the knee without joint effusion can be prominent. Range of motion can be limited in the last 10 degrees of extension because of pain in the area of the MCL. The valgus stress test is the pathognomonic test for MCL tears. This test is done with the knee in 30 degrees of flexion as well as 0 degrees. Pain along the MCL or increased opening compared to the contralateral knee with valgus stress with the knee in 30 degrees of flexion, but not 0 degrees, suggests an isolated MCL tear. If there is also laxity at 0 degrees, this suggests a concomitant ACL tear, posterior cruciate ligament (PCL) tear, or fracture. Laxity is furthermore classified as with or without an endpoint and graded as I, II, or III with 0- to 5-mm, 6- to 10-mm, or >10-mm increased opening, respectively.

Stress X-rays and ultrasound can be used, but MRI is the gold standard radiological test. While rarely necessary to identify an MCL tear, it can help show the severity and location, as well as any other soft tissue injuries that may have been masked on exam.


Initial treatment of isolated MCL tears is nonoperative. For grade I tears, physical therapy with modalities including ice, as well as range of motion and strengthening exercises, may be all that is needed. A knee sleeve provides additional comfort. Preventing stiffness allows a quicker recovery. A hinged brace may allow earlier return to play while the MCL is healing if there is no pain at the MCL during play.

For grade II and III tears, a double upright hinged brace is necessary and often allows the ability to ambulate without assistive devices. Distal tears may benefit from the addition of some sort of stem cell injection, because these injuries heal with more difficulty. The brace is worn for four to six weeks, but physical therapy can be added earlier. If there is an ACL or PCL injury as well, surgery is more often required. Injuries to both the MCL and ACL can be treated by repairing the MCL while reconstructing the ACL, but many times the MCL can be treated nonoperatively with a brace during the four weeks of preoperative-condition therapy needed for successful ACL surgery. If the MCL heals nonoperatively before the ACL is reconstructed, it does not need to be addressed during the ACL surgical procedure. This may also lead to better long-term outcomes versus early repair of MCL combined with ACL reconstruction.

Physical therapy goals focus on regaining full range of motion and strength. As progress is made and the MCL heals, the athlete should complete an exercise program for lower limb strengthening with emphasis on the hip muscles. When doing inner and outer thigh strength exercises, the athlete should take care not to stress the MCL. Ice can be applied after exercise to reduce swelling and pain.

Return to Action

Recovery may take up to three months but depends upon the severity of tear as well as the particular sport’s demands. Many athletes can return during the healing process in an MCL playing brace, as long as they do not have pain at the MCL while in the brace. They should progress slowly and gradually increase the amount of time spent in their sport. Athletes should master running and cutting drills before beginning full participation.


Common Causes

Rupture of the ACL is the most common season-ending knee injury. It is more common in females, with many reasons postulated, including anatomic differences in the femoral condyle in females that cause a tighter area for the ACL to travel through, that is, an “A” notch; thinner ligaments; estrogen levels; increased femoral rotation; and poor jump-landing techniques with a knock-knee position. Studies have shown that early teaching of improved landing techniques can decrease the rate of ACL tears in females.

Anterior cruciate ligament tears are common in all athletes, with contact and noncontact mechanisms. Both “plant and twist” and hyperextension mechanisms can result in ACL tears. The former is common in cutting sports such as soccer, basketball, tennis, football, and skiing. The latter can happen when landing in a small depression while running on a field. Both can occur with awkward landings. Avulsion of the tibial eminence (area of bone on the tibia where the ACL attaches) is more common in preadolescent athletes, resulting in an ACL deficiency, while the ligament tears (and not the bone) in adolescents and adults. The ligament stretches before it tears, so the majority of partial tears can result in an ACL-insufficient knee and still may require operative intervention. Other injuries such as meniscus or other ligament tears are not uncommon in conjunction with ACL tears and must be identified to decide on proper timing and extent of treatment necessary.


Most athletes will describe a shift of the knee as if the knee dislocated and came back together. They may hear or feel a pop, but pain may or may not occur. Often, there is no associated pain. Swelling is immediate, and most athletes cannot continue competing. In cases in which there is little swelling, it may be that the tear is chronic or, at times, more significant. If the tear is extensive, there may be minimal swelling directly within the knee because the swelling may be diffusing out of the knee capsule and into the lower leg; thus less concentrated local swelling is noted in the knee. The more typical substantial and immediate swelling is caused by a hemarthrosis, due to tearing of the blood vessel in the ACL. Pain is more likely from the bone bruise sites than typically occurs with an acute tibial translation episode. Following an ACL tear, the knee buckles and feels unstable, or may feel as though it hyperextends. Gait can be affected with what is termed an ACL avoidance gait pattern.

Tests on physical exam include the Lachman, anterior drawer, and pivot shift tests. The Lachman is the gold standard, and is performed with the knee in 30 degrees of flexion. Increased laxity to anterior stress of the tibia in this position is a positive test. Lack of an endpoint is associated with higher-grade tears. As with all knee ligaments, the same grading system exists: 1 to 3 with increments of 5-mm difference compared to the contralateral knee. Range of motion is usually decreased after a tear. X-rays may show a Segund sign, which is a small avulsion of the lateral capsule and is pathognomonic for an ACL tear. Some believe this is related to the avulsion of an accessory lateral ligament, which may or may not need to be repaired as well.

Magnetic resonance imaging is again the preferred radiological test. Besides confirming the tear, it can identify bone bruises suggesting an acute anterior tibial translation episode (anterior lateral femoral condyle and posterolateral tibial plateau bone bruising) and other concomitant injuries such as meniscus tears. The bruises occur in the pivoting mechanism as the lateral knee subluxates and then pops back into place, “kissing” these two areas of bruised bones during the relocation. The medial knee joint does not subluxate in these cases. In hyperextension mechanisms, there can be different patterns of bone bruising.


Age, occupation, desired activity, sports involvement, and associated injuries to the knee are all taken into consideration when deciding on treatment for an ACL tear, but the standard of care for almost all ACL tears is to reconstruct it. In the latter part of the last century, patients were not offered reconstruction if they were past their 20s and not a high-level athlete. This is no longer the standard of care, and most patients are reconstructed. The ACL fibers stretch prior to tearing, and therefore repairing (rather than reconstructing) an ACL may result in a persistently lax ACL. Some surgeons are revisiting repairing ACLs and are showing improved results from past techniques. Nonoperative treatment is an option if the thigh muscles can be returned to full strength and instability episodes are minimized.

A dynamic ACL brace is a relatively newer option. This brace can help prevent subluxation of the tibia. However, a functioning ACL is paramount to normal mechanics of the knee, contributing not only to stability but also to the normal motion of the knee. The natural history of an ACL-deficient knee is for it to become arthritic, but recent studies have shown that even with a perfect ACL reconstruction, arthritis does develop an average of 12 years after the injury in the majority of patients.

After the injury, the knee is weak and has lost range of motion. Regaining strength and regular motion with a supervised physical therapy program prior to undergoing reconstruction has been shown to improve long-term function and return to previous levels of competition. This usually takes approximately four weeks from the time of injury, and most ACL reconstructions are therefore delayed until the knee is strengthened.

Delaying surgery until there is full range of motion and strength and no swelling is one reason that modern athletes have the opportunity to fully return to sports after an injury that was thought career ending just a few decades ago. Advances in surgical techniques, including anatomic arthroscopic ACL reconstruction placing the reconstructed graft in optimal location, improved graft options, thicker grafts or double bundle grafts or both, fixation techniques and hemarthrosis prevention, early postoperative motion, and improved physical therapy techniques also contribute to regaining normal performance.

Young athletes with open growth plates may be braced and surgery delayed until their physes close, thereby allowing drilling across the growth plate site without risking growth abnormalities. Avoiding placing bone plugs across a growth plate and physeal sparing techniques allow earlier reconstruction in this population. Meniscus repair techniques may be more successful in this age group as well.

Even patients in their 60s and older are now reconstructed to allow normal knee mechanics and sports such as skiing and basketball. Life expectancy continues to increase, and so does sports life expectancy. An individual athlete’s goals should always be accounted for in the decision on treatment, regardless of age.

There are a few broad stages of recovery after ACL reconstruction: reduction of swelling and pain, ability to ambulate (and return to office work or school if not a professional athlete), graft healing in the bone tunnels (femoral and tibial), regaining full motion and strength, graft maturation, and return to sport to the preinjury performance level. The timeline may be affected by concomitant meniscus or other ligament repairs, but isolated ACL reconstructions routinely do very well. Use of autograft (bone-patella-bone [BPB], hamstring, quadriceps) or allograft (BPB, hamstring, Achilles tendon, posterior tibialis) can affect the timeline also.

Surgery is done as an outpatient procedure. Many surgeons now use regional blocks (femoral or adductor) or general anesthesia or both. The first week is best spent at home elevating the knee and using a continuous passive motion machine as well as an ice machine. Elevating the leg and using ice help reduce swelling, which is a cause of postoperative pain. As part of a multimodal approach that also includes over-the-counter medication such as acetaminophen and NSAIDs (unless contraindicated), most patients can avoid opioid pain medications whose usage is a current problem in the United States. Formal physical therapy is then added to help continue to reduce swelling while assisting in regaining motion and strength. Initial concentration focuses on regaining full extension equal to that on the contralateral side because this helps the ACL graft fit into the notch properly. Not doing this can lead to osteophyte formation within the anterolateral notch and subsequently graft impingement, which may lead to anterior knee pain, swelling, and quadriceps atrophy. This results in decreased performance, persistent knee swelling, and potential stretching of the graft. Later concentration is placed on regaining full flexion while continuing to regain full hamstring and quadriceps strength. The knee will not feel normal until it has full range of motion and strength.

The graft is usually healed into the bones by six weeks based on computed tomography (CT) studies, but the graft takes much longer to mature as new blood vessels grow into it and it remodels. Because the graft is weaker during this time, the risk of tearing a graft is initially higher; it gradually decreases until about nine months out, when it plateaus. This is part of the reason many surgeons will advise against return to play prior to 9 to 12 months, but the increased rate of tear may be only a few percentage points at three to six months. The informed choice should be made jointly between the patient and surgeon. Once the muscles show 90 percent strength, a progressive return to play should be considered in a playing brace if the player is willing to accept the increased risk. After one year, the brace is rarely needed, but many athletes continue to use it, perhaps as a psychological crutch.

Overall, graft tear rates are actually lower than contralateral knee ACL tear rates. Anterior knee pain is now known to be attributable to lack of extension and is preventable. Strengthening the hip muscles during therapy is also extremely important in helping to restore stability in the lower limbs and decrease strain on the reconstructed ligament.

Return to Action

While some athletes can return to sports as early as three to four months, the majority who have undergone good surgical techniques combined with proper physical therapy can return in four to six months. Because multicenter studies have shown a slightly higher retear rate until nine months, many professional teams will not risk their athletes earlier than this, even though they may physically be able to play, because of long-term play considerations. Graft choices with regard to tear rates also equal out around that time with respect to reinjury. Some studies have suggested a higher retear rate in younger high-level athletes with allografts, but the risk is only slightly higher when one combines all allografts (graft tissue from a source other than oneself), and certain allografts (just as with certain autografts, one’s own tissue) have better rates than others. Regardless of graft type, the highest rate of failure is in the 10 to 19 age group, but sex is not a risk factor. The native ACL is 33 mm long and 13 to 14 mm thick, with the anterior bundle and posterior bundle fibers acting differently depending on the positions of flexion of the knee.

Thicker grafts may replicate this better and therefore have better outcomes. Thicker grafts or aperture fixations (or both) also decrease the amount bleeding into the joint postoperatively and help the recovery as well. Proper rehabilitative therapy has been proven to reduce the risk of recurrent ACL tears by 40 to 60 percent, and therefore it is imperative that athletes undergo training programs before returning to sport. The bottom line is that when surgery and rehabilitation are done properly, most athletes will return to full form.


Common Causes

Injuries to the PCL occur when a posterior force is directed onto the upper tibia. This typically occurs during a fall onto a flexed knee or a dashboard injury in a car. The PCL can also be injured with trauma to the anterior portion of an extended knee, or during a hyperextension injury. Posterior cruciate ligament injuries are often perceived by the athlete as a simple sprain, and they do not often seek treatment. However, mild symptoms can linger on for years. When the injury is more unstable, the reason is often that there are associated posterolateral corner or ACL injuries as well.


Posterior cruciate ligament injuries are much less common than ACL injuries. The athlete will express that the knee doesn’t feel right but cannot clearly identify the problem. There can be pain, mild swelling, and no perceived instability. However, the injury can be debilitating and affects the ability to run at full capacity because of a sense of not being able to trust the knee. Positive physical exam findings include a positive quadriceps active test, posterior drawer, and posterior sag. Posterior lateral corner injuries will have increased external rotation at 90 and 30 degrees of knee flexion. Magnetic resonance imaging easily confirms the diagnosis and rules out other associated injuries.


Most PCL injuries are treated without surgery, and new dynamic PCL braces can help keep the tibia forward during activities. The PCL is more likely to heal than an ACL tear. Extensive rehabilitation is often necessary, with a focus on strengthening the quadriceps muscles because these muscles add stability to the PCL-deficient knee. Surgery is reserved for combined injuries and severely unstable isolated injuries. Modern techniques such as the inlay reconstruction technique have improved outcomes, but many patients have mild residual 1+ instability postoperatively.

Return to Action

It can take three to six months of physical therapy to get maximum improvement with nonoperative treatment. Six to 12 months are required to rehabilitate the surgically reconstructed knee, especially when other repairs are made during the surgery. Once the knee has full motion and strength, is pain free, and the athlete passes a series of functional knee tests, return to activity is permissible, usually with a post-op brace. A progressive program specific to the sport needs to be followed to maximize outcomes safely.


Common Causes

Injury to the lateral collateral ligament (LCL) occurs with a varus mechanism, with the force directed from the medial side of the knee toward the lateral side. A direct blow from an opponent is one way this occurs, but a misstep or figure-four injury during martial arts could also cause the damage.


In this type of tear, the athlete feels pain on the outer side of the knee along the LCL. Sitting cross-legged or in a figure-four position causes pain. There is tenderness to the LCL vertically as opposed to horizontal joint line tenderness. A positive varus stress test at 30 degrees of flexion and not 0 degrees is the gold standard test. Dial rotation test should be checked to rule out more extensive posterolateral corner structure tears. ACL, PCL, and meniscus tear tests should also rule out injuries that may require surgery; most LCL injuries do not. Magnetic resonance imaging again is the radiological test of choice.


Most isolated LCL injuries can be managed nonoperatively with a brace if necessary and physical therapy. More unstable injuries, especially those associated with other ligament or posterolateral corner injuries, may require repair or reconstruction of the LCL or both. Meniscus surgery rarely requires concomitant LCL repair or reconstruction, and the latter component can be treated with a brace. Care should be taken not to stress the ligament while doing arthroscopic surgery for a meniscus. This may require delay of the meniscus surgery until the LCL is healed.

For grade I and II LCL injuries, the athlete should begin active and passive range-of-motion exercises immediately, ice, and quadriceps and hamstring strengthening exercises. Supervised physical therapy should accelerate recovery. No bracing is required unless there is a grade II or III injury or the knee is painful without it. Usually a knee sleeve is all that is needed with regard to bracing, perhaps with flexible stays. Bracing for LCLs often requires only four weeks, but occasionally six weeks are needed. Caution with hip exercises should be observed to avoid stressing the outer leg and LCL.

Return to Action

Return to sport is 4 to 12 weeks. Athletes typically use a knee sleeve with supports on the medial and lateral sides as they return to activity. They should progress slowly and perform exercises that mimic their sport before attempting full participation.


Common Causes

Patellar tendinitis is commonly known as runner’s or jumper’s knee, because it is most associated with repetitive running and jumping sports and is an overuse injury. Basketball players and long-distance runners are most commonly affected, along with volleyball players. Often there is a chronic degenerative component (tendinosis), with an acute inflammatory component (tendinitis). Young athletes rarely have the degenerative component but may have apophysitis or osteochondrosis, which can be ruled out with an X-ray.


The hallmark of patellar tendinitis is localized pain in the proximal portion of the patellar tendon near the lower part of the patella. The pain is aggravated by jumping and running and not typically related to any single traumatic event. It usually starts during participation in the sport. The pain will stop after the activity is stopped in grade I injuries. Grade II injuries will linger on a bit following activity cessation. Grade III is constantly painful, while grade IV represents a tear of the tendon. It is important to try to avoid progression to a grade IV tear. Pain can limit running and jumping but may also affect stair climbing and sitting (different from chondromalacia patella). Swelling may indicate bursitis anterior to the tendinitis and is not usually present. Calcific tendinitis is rare in this area but can be severely painful with a sudden onset unrelated to activity. Ultrasound and MRI scan can identify areas of degeneration and partial tearing.


The initial treatment is activity modification and rest. A patella tendon strap may allow continuation of sport while undergoing treatment if there is not pain with use. Ice and NSAIDs may help reduce the acute inflammatory component but will not affect the tendinosis if present. An exercise program emphasizing quadriceps stretching and strengthening helps prevent recurrent symptoms. If symptoms persist, surgical treatment can be considered. Traditionally, this involved a small incision with simple debridement. Minimally invasive procedures such as microdebridement treatments followed, but have more recently been replaced with percutaneous techniques under ultrasound guidance with equipment that break up and remove the degenerative areas. This technique is indicated after six weeks of failed treatments. While traditional open surgical treatment could take three months of recovery and more, the newer percutaneous treatment often requires six weeks. Cortisone injections are contraindicated in this area because they can increase the risk of patella tendon tear. Platelet-rich plasma and stem cell injections, especially with vascular channeling techniques, show significant promise and should be considered prior to resorting to surgery, or can be done as adjunct to the percutaneous microdebridement.

Return to Action

Return to sport is highly variable with nonoperative treatment, and is indicated approximately six weeks following the percutaneous debridement procedure. Stem cell injections can also take six to eight weeks to produce improvement. Repetitive treatments may be required.


Common Causes

Fracture of the patella is almost always caused by a direct blow to the knee with some object, collision with another athlete, or a direct blow to a flexed knee. This injury can occur in any sport and causes significant disability, but luckily is not that common. It may also occur after ACL reconstruction with use of the BPB autograft techniques, especially if the bone plug graft site in the patella is not backfilled with bone graft during closure. This area can act as a stress riser (i.e., an area with an increased risk of fracturing) if the athlete lands on it.


Fracture of the patella causes immediate pain, swelling, reduced active motion, deformity, and difficulty walking. A knee immobilizer should be used and X-rays performed.


If the fracture is not displaced and no articular surface step-off is seen, it may be managed nonoperatively with a knee immobilizer for four to six weeks. Weight bearing as tolerated can be performed with the brace on. Younger athletes should be placed in a cast, because they are more likely to remove the immobilizer. A bone stimulator can be used to try to speed up the healing, but is contraindicated in young athletes with open growth plates and is reserved for older adult patients.

Vertical fractures can sometimes afford earlier motion exercises under the guidance of a trained physical therapist, depending on the fracture pattern. Horizontal fractures, which are more common, are at greater risk for displacing with motion because of the “tug-of-war” pull on the fracture fragments by the quadriceps and patella tendons. If there is significant displacement or articular surface step-off, surgery is required to reduce the fracture and articular surface (to prevent arthritis), using tension band and other techniques. The knee is immobilized postoperatively for a shorter time than without surgery, which allows earlier range-of-motion exercises. Weight bearing status while in a brace or cast will depend on the fracture pattern, quality of the bone, strength and type of fixation, and surgeon’s preference. Quadriceps atrophy can be an issue and needs to be addressed early in therapy.

Return to Action

Return to sport can take four to eight weeks after the fracture is healed, but could take months if the quadriceps atrophies. The athlete must regain motion and strength prior to sport-specific exercises in preparation for return. Contact sports should be delayed usually until four to six months of healing.


Common Causes

Instability of the patellofemoral joint can cause disability and poor performance due to maltracking and lateral compression syndrome (increased pressure of the lateral aspect of the patella onto the femur). There is an increased risk of patella dislocation because of the increased vector pull. A quick, violent hyperflex of the knee in conjunction with a twist or rotation of the lower leg can result in a patella dislocation. Recurrent dislocations may require surgery, while simple maltracking rarely requires it. Traumatic dislocations in athletes over 30 years of age rarely recur and should be treated nonoperatively unless there is recurrence or persistent symptoms are present.


Dislocation of the patella is a significant event although the athlete may not realize that a dislocation occurred if it spontaneously reduces. It can feel very similar to an ACL tear and is often confused with the tear. However, when spontaneous relocation does not occur, the athlete is in tremendous pain and the leg is grossly deformed because the kneecap is off to the side, exposing the femur under the skin. Straightening the leg may allow reduction. Following a patellar dislocation and relocation, there is often tenderness over the medial aspect of the knee due to a tear of the medial patellofemoral ligament (MPFL) and retinaculum (which occurs as the patella dislocates laterally). A positive apprehension sign is present. An apprehension sign is positive when the examiner pushes the patella toward the direction of dislocation and the patient shows an apprehensive response such as being startled.


Treatment of an acute patellar dislocation depends on the age of the patient, underlying anatomical considerations, and history recurrences. Reduction must be done as soon as possible, and if it is not possible in the field, the athlete should be taken to an emergency room to have the reduction. If X-rays after reduction show no fracture, a patella tracking orthosis (PTO) can be tried for six weeks to allow for healing and then stability assessment. Some doctors advocate using a simple knee immobilizer for two weeks followed by an aggressive rehabilitation program emphasizing quadriceps and hip muscle strengthening. Loose bodies should be ruled out with X-rays and may need to be removed with an arthroscopy. Large OCD fragments may need to be fixed with open surgical techniques to preserve articular surface. Some surgeons advocate immediate MPFL reconstruction, but there is no urgency in doing this unless the kneecap is recurrently dislocating. Magnetic resonance imaging can be helpful. Older athletes rarely dislocate a second time, and surgery should be avoided unless they experience a recurrence.

Return to Action

Once the apprehension sign is negative and the athlete has full motion and strength, it is safe to return to play. This is usually around 10 to 12 weeks. Athletes may continue to use the PTO for the first year postinjury. If surgery is required, the return to sport is typically longer, especially if tibial tubercle osteotomy and transposition is required. This can take 6 to 12 months, because there is significant scarring, loss of motion, and atrophy after surgery that needs to be corrected with therapy. Surgery has a high rate of success in preventing further patellar dislocations, but some pain may persist due to the articular surface damage.


Common Causes

Osgood-Schlatter’s syndrome is a painful condition affecting growing children, caused by repetitive microtrauma and pulling by the distal patella tendon on the tibial tubercle apophysis. This essentially causes repetitive microfractures that heal, break, heal, break, and so on, causing a large visual bump on the knee just below the kneecap. Symptoms tend to be caused by running and jumping activities. Pain is the presenting symptom. Once the growth plate closes, symptoms usually subside.


Osgood-Schlatter’s is characterized by well-localized tenderness of the tibial tubercle. Swelling can be related to an adjacent bursitis. Prominence of the tubercle is present. Adults with a history of Osgood-Schlatter’s might continue to have episodic pain at the tibial tubercle especially if there is an unfused ossicle (a small loose piece of bone). This can be seen on the lateral X-ray view, MRI, or CT scan.


Treatment of Osgood-Schlatter’s syndrome requires rest from jumping and running activities. Immobilization is rarely necessary but can help in certain cases. Treatment is palliative with ice massage, stretching, and strengthening exercises. Nonsteroidal anti-inflammatory drugs can be added for up to seven days if needed. Surgery is rarely required in adults who do not respond to treatment. Usually, this requires only excision of the ossicle.

Return to Action

Return to sport is allowed once symptoms have resolved, usually in a few weeks. Recurrence is possible until the growth plate closes.


Common Causes

Osteochondritis dissecans (OCD) is usually caused by repetitive trauma, while an osteochondral defect lesion (OCDL) can be from a single traumatic event. A fragment of subchondral bone in the knee joint becomes loose and leads to vague pain and disability. This condition is most common in athletes undergoing repetitive stresses across the knee. Athletes participating in gymnastics and baseball have a higher incidence.


Osteochondritis dissecans usually occurs before the age of 18 and is twice as common in males as in females. It is most common in the lateral aspect of the medial femoral condyle, followed by the posterior aspect of the lateral femoral condyle. There is joint line tenderness but a negative McMurray test. The Wilson test can be positive. Loading of the joint causes pain. Athletes may rotate the lower leg when walking to relieve pressure on impact. Pain is most notable during weight bearing, especially in extension. X-rays usually reveal a lesion on the femoral condyle, but sometimes an MRI is necessary to see the defect in earlier lesions. Magnetic resonance imaging is helpful in estimating stability of the lesion. If there is fluid around the bone lesion, it is felt to be unstable. An OCDL is usually traumatic and is more commonly found in older athletes. It may start out as just a chondral injury, but exposed bone may break down. If edema is present in the subchondral bone, surgical correction may be required.


Reducing the stress on the lesion may allow it to heal. Crutches and non-weight bearing are often helpful in the younger population. Improvement may take several months. Surgical treatment in the younger population may include stabilization of the lesion. Adults often will require excision of the fragment and some sort of resurfacing technique, which depends on the extent of injury to the subchondral bone. This may include OCD allograft or autograft mosaicplasty, but if the bone defect is shallow, chondral resurfacing techniques alone may be tried but are still experimental.

Return to Action

Whether treatment is conservative or operative, recovery time can be six to eight months. Smaller lesions in adults with OCD allograft plugs 10 mm or less may sometimes allow an earlier return. Follow-up X-rays should check for healing before return to play is allowed. Range of motion and strength should be at full capacity before return to play. Unloader braces can be used in the postoperative period or during nonoperative treatment (or both) to reduce the load on this area.

*The author would like to acknowledge the contribution of Michael Kelly and Yvonne Johnson to this chapter.

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Apr 16, 2020 | Posted by in SPORT MEDICINE | Comments Off on Knee Injuries
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