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The Knee

The knee is a complex joint that not only bends and straightens but also twists and rotates. The knee is not a simple ball-and-socket joint, like the hip. It depends heavily on the soft tissues that surround itthe muscles, tendons, and ligamentsbecause it's a weight-bearing joint that is subjected to many different types of motion. This variety of motion can lead to tearing of the cushioning cartilage inside the knee and of the supporting ligaments on both sides of and inside the knee.

      A thick pad of cartilage acts as a cushion and stabilizes the structures between the two bones of the knee. The two lower knuckles of the femur (the thigh bone) are called condyles. These condyles sit on top of the flat surface of the tibia, the large shin bone. Inside the knee, between each condyle and the tibial surface are two half-moon-shaped cartilages, the medial meniscus and the lateral meniscus.

      The knee joint is basically held together by four very strong ligaments. The medial and lateral collateral ligaments provide side-to-side stability. They are found on the inside and outside of the knee between the thigh bone and the shin bone. The anterior and posterior cruciate ligaments provide front-to-back stability. They are inside the knee. The anterior cruciate runs from the front of the shin bone to the back of the thigh bone, and the posterior cruciate runs from the back of the shin bone to the front of the thigh bone. They cross in the middle, and that's why they are called "cruciate," which means cross-shaped. The cruciate ligaments allow you to come to a sudden stop and to accelerate suddenly.

      Because of its structure, the knee is extremely susceptible to blows from the side. It also can be severely damaged by rotating, twisting forces. The joint is very well designed for its intended functions, but it is the most poorly designed of all the joints in the body to withstand the forces of athletics. When God created the knee, He didn't have football in mind.

      The knee is the most commonly injured joint in the body, accounting for about one-quarter of all injuries. Nearly one million knee surgeries are performed each year. Between acute traumatic and overuse injuries, I see about six or seven patients with knee damage every day in my practice. A knee injury is also the injury most likely to end an athlete's career.


You can sprain your knee by twisting it in a fall, by stepping in a hole while running, or by being hit from the side while playing sports. The knee will swell up, and you will have trouble walking on that leg.

      A knee sprain, by definition, is an injury to a knee ligament. The sprain may vary in severity from a slight stretch to a complete tear of the ligament. A mild, or grade 1, sprain simply stretches the ligament and causes pain and swelling. A moderate, or grade 2, sprain partially tears the ligament and is much more disabling. A severe, or grade 3, sprain is a complete rupture and often needs surgical repair.

      The most commonly sprained knee ligament is the medial collateral ligament (MCL). This ligament can be sprained by a blow to the outside of the knee, particularly if your foot is planted in the ground when you are hit. The blow causes the knee to move toward the inside of the body and stretches the ligament. You will feel tenderness and pain on the inside of the knee, and the knee will feel like it may buckle or give way to the inside. Anything more than minimal pain should be treated by a doctor.

      A sprain of the ligament on the outside of the knee, the lateral collateral ligament, is caused by a blow to the inside of the knee, which forces the knee to the outside. This is much less common than an MCL sprain because it is hard to get hit on the inside of the knee. Usually, your other leg gets in the way and takes the blow.

      Here's a good rule of thumb for knee injuries: If you receive a blow to the knee and the pain is on the same side of the knee that was hit, it's probably just a bruise, and the pain will go away rapidly. If the pain is on the opposite side of the knee, consider this a serious injury that needs careful treatment.

      The immediate treatment for a sprained knee is the standard RICE formula (see Chapter 4). Rest the knee while it aches and ice it intermittently several times a day. Wrap it in an elastic bandage in between icings and keep it elevated as much as possible.

Knee Sprain Rehab

If the MCL sprain is a mild one, an early rehabilitation program using a stationary bicycle and leg extension and curl exercises is all you need.

      Begin by riding a stationary bicycle for 20 minutes. Keep the seat high so that your range of motion is minimal. Don't put any drag on the bike; you are simply interested in moving the knee. In the very beginning, you may not be able to pedal all the way around. Just pedal back and forth until you can come over the top. Once you can do this, lower the seat gradually so that you increase the bend in your knee each day until you get back your full range of motion.

      Do the Leg Extension while seated at a bench or a table (see the strength-training program in Chapter 1). Once you lift the weight, hold at full extension for three seconds and then very slowly lower your leg. Concentrate on the slow movement down, which is the most important part of the lift. Muscle contraction against weight while the muscle is lengthened builds the most strength.

      Ten lifts make a set. Do five sets of this exercise and rest for 30 seconds or more, if needed, after each set. Start with no weight and gradually add weights (5 pounds for men, 2.5 pounds for women) until you reach the amount of weight necessary for you to fail during the last set. Use ankle weights, or a weight boot, or hang an old tote bag or pocketbook filled with weights from the ankle.

      Do the Leg Curl while lying on your stomach (see the strength-training program in Chapter 1). Again, do 10 lifts per set for five sets. If you are using a weight machine, you should hold for three seconds with the leg bent. If you are using free weights, this is not necessary.

      The purpose of these exercises is to strengthen the quadriceps muscles in the front of the thigh (leg extensions) and the hamstring muscles in the back of the thigh (leg curls). These muscles, particularly the quadriceps, begin to lose strength within 12 hours of a knee injury. These muscles control the knee and must be restrengthened.

      If you have a problem doing the leg extensions, that is, if your range of motion is too limited or you find it too painful, then do isometric quadriceps exercises first.

      Anything more severe than a minimal knee sprain should be seen by a physician. You will then need to begin a rehabilitation program that consists of more sophisticated strengthening exercises, perhaps using isokinetic machines, bracing, and physical therapy.


If the force to the side of the knee is more severe, or if you are rotating your knee when you are hit, then the anterior cruciate ligament (ACL) may be stretched or torn. Probably the most severe ruptures I see are caused not by trauma but usually by a heavy athlete, such as a football lineman, running and then planting his foot and turning 90° to go upfield. This twisting can cause a complete ACL rupture. Giants punter Sean Landetta missed the last half of the 1992 season when he turned to make a tackle and ruptured his ACL without anyone touching him.

      If your ACL ruptures, the loud pop may be heard by your teammates. You will feel sudden pain and instability in the knee. The knee will swell up rapidly because the ACL bleeds quickly when injured. Any ACL injury causes symptoms profound enough for you to seek professional help. You cannot treat an ACL injury yourself.

      An MRI scan may help determine whether the ligament is stretched or totally torn. If it's torn, it will need to be repaired surgically, although an older athlete may be able to get by without surgical repair. Modern methods of repair through the arthroscope plus new ideas on rehabilitation, such as beginning exercises immediately after surgery, have dropped recovery time from 12 to 15 months to 6 to 7 months. Even so, rehabilitation is a major undertaking.

      The arthroscope allows complex surgical repairs to be made through a few small holes in the skin. Arthroscopy works best on the knee because the knee has sufficient space for the scope to slip easily among the bones, cartilage, and other tissues. The benefits of successful arthroscopy include less pain, less chance of infection, a shorter recuperation period, and lower medical bills.

      There are also rehabilitation programs for a partially torn ACL. Done under a physical therapist's guidance, they center on the use of isokinetic exercise machines, which are much more efficient than regular free weights or the weight machines in gyms. These machines resemble isotonic devices, such as the Nautilus® leg extension machine, but the isokinetic machines vary the resistance with the amount of pressure applied. The more effort you expend, the more resistance you encounter. Your effort is recorded by a computer and displayed on a screen or printed out on paper.

      Once your rehabilitation is complete, very sophisticated knee braces are available that will allow you to return to full activity, even if the ligament has been totally torn and not repaired.

      Posterior cruciate ligament (PCL) injuries are very rare and usually are due to a head-on blow to the knee. You will feel pain and some swelling, and you will not be able to accelerate without severe pain. This ligament will usually heal itself.

      Two Giants linebackers, Carl Banks and Gary Reasons, had PCL injuries and returned to action in three to four weeks. Only tight end Mark Bavaro's PCL tear did not heal and required surgery. Philadelphia Eagles quarterback Randall Cunningham required surgery because he tore both his PCL and his MCL, which resulted in instability.


A hit on the outer side of the knee causes the inner side to stretch. This can cause one of two things to happen. The MCL, which is attached to the cartilage, can tear the cartilage as it stretches. Or, when the stretching force is removed, the inner side of the knee can close again with some force, driving the condyle back into the cartilage just as the spring hinge of an old screen door slams the door back into the frame.

      The grinding action on the knee as it rotates can also damage cartilage. This grinding action is similar to that of a mortar and pestle, with the cartilage the substance being crushed. The same thing happens when the femoral condyle rotates on the tibia with all of your weight compressing it.

      If you tear some cartilage, you will feel pain and see swelling in the knee, but usually not as much as with an ACL tear. The pain may be on the inside or the outside of the knee, depending on which cartilage has torn. You may hear a clicking sound inside the knee when you move it; this is the bone riding over the torn part of the cartilage. When you move laterally or twist your knee, the knee may slip and buckle and even cause you to fall. Many of my patients with torn knee cartilage complain that they can't make a sharp turn even when walking.

      The knee may be locked so that it is impossible to extend it fully or bend it. Remember, the knee is a hinged joint, and if a piece of cartilage tears and flops over, it impedes the hinge from working. Just as sticking a pencil in a door will prevent the door from closing all the way, the knee joint won't open or close fully if a piece of cartilage is stuck between the two bones.

      Most cartilage tears do not heal by themselves. Cartilage has a poor blood supply except at the outer rim, so about 90 percent of cartilage tears have no ability to heal. Tearing a cartilage is similar to tearing a fingernail. A torn fingernail won't heal by itself; you have to wait for the nail to grow out, and then you cut off the torn part.

      Unfortunately, cartilage does not grow back, but the torn piece still has to be cut out. The most common way is to shave down the ragged edges of the tear with tiny instruments manipulated through an arthroscope. Arthroscopic surgery is minor surgery in an expert's hands. There is no real excuse for opening up a knee for a cartilage repair except in the most unusual cases.

      If the tear is at the outer edge of the cartilage, or if it is small, it may heal. Healing requires a rehabilitation program similar to that described for the MCL to restrengthen the muscles around the knee. By following the rehabilitation program, you can usually return to full activity within three or four weeks.


A very severe injury to the knee, and one common among athletes, is called the Terrible Triad of O'Donohue, named after a long-time team physician at the University of Oklahoma and one of the deans of sports medicine. He was the first to describe this injury, which consists of an MCL sprain or tear, an ACL tear, and a medial cartilage tear, all due to a single blow to the knee.

      This devastating injury requires complete surgical repair. It's impossible to rehabilitate all of these structures and have a functioning knee again without surgery.


An extremely severe traumatic injury to the knee, and one of the few true orthopedic emergencies, is total dislocation of the knee. This is caused by a blow that tears the whole knee out of the socket. The lower leg moves away from the upper bone, and the only thing really holding the lower leg together is the skin. This can cut off the blood supply to the lower leg and necessitate amputation if not rapidly relieved.


The kneecap (patella) is the bone covering the tendon that runs from the quadriceps muscle in the front of the thigh to the bone beneath the knee. This tendon is responsible for holding the leg straight so that you can stand erect, and also for straightening a bent leg for climbing stairs or riding a bicycle.

      The back of the kneecap is shaped like a wedge and rides in a V-shaped groove in the front of the lower end of the thigh bone between the two condyles. If the kneecap is hit at an angle, it can be knocked out of this groove. The kneecap almost always dislocates to the outside since the outer lip of the groove is much shallower than the inner lip.

      A dislocated kneecap causes pain, and the knee will appear deformed since the kneecap will sit way out to the side. Usually, it can be popped back into place by a doctor without too much difficulty. It may even pop back in by itself on the way to the doctor's office or emergency room. Even if it pops back in, however, you must have it x-rayed to make sure a piece of bone has not been knocked off the undersurface. Occasionally, the kneecap is locked out of place so severely that surgery is needed to put it back in place.

      A dislocated kneecap requires immobilization in a splint for about three weeks to allow the tissues on either side of the kneecap to heal. These tissues are responsible for holding it in place, and if they remain torn, the kneecap will be prone to dislocate again. Interestingly, the kneecap groove is much shallower in girls than in boys, so dislocation is a more common, recurrent problem among girls.

      After a period of rest, the athlete must strengthen the quadriceps with a program similar to the one outlined for the knee ligaments. Start with isometrics and then progress to Leg Extensions (see Chapter 1). These exercises will tighten the kneecap back down by increasing the tone of the muscles pulling on the tendon underneath it. This will hold the kneecap in the groove so that it won't be likely to pop out again.


The kneecap may fracture from a head-on blow. Usually, this causes pain and swelling, and the kneecap will need to be x-rayed. The x-ray must be interpreted by someone very familiar with kneecaps. In many people, the kneecap naturally forms in two pieces and never unites, and this can be misinterpreted as a break.

      A broken kneecap needs to be immobilized and may even need surgical repair, depending on the direction of the fracture line. If the fracture line is vertical, immobilization should be enough. If the fracture line is horizontal, then the two pieces will be pulled apart by the quadriceps and will need to be wired together until they unite.


If an athlete has sudden episodes of knee pain and knee locking, there may be a loose body floating inside the joint. The onset of these symptoms may not appear for months to a year after a traumatic injury, such as a blow to the knee. Just as suddenly as the pain comes on, it disappears and you have your full range of motion again.

      These on-again, off-again symptoms are due to a loose body in the knee getting caught between the upper and lower bones, causing pain. When the body floats back up into the hollow space in the knee, out of the way, the pain is relieved.

      The loose body may be a piece of cartilage that has torn off or a piece of bone that has chipped off. The bone may have been injured before. It gradually dies, and a piece can fall off the bone and float inside the knee.

      You may be able to feel the loose piece along the edge of the knee joint. It may feel like a pea that suddenly floats into the knee under the pressure of your weight and then suddenly disappears.

      Arthroscopic surgery is necessary to remove the loose piece and stop the symptoms.


The most common overuse injury to the knee, and the most common cause of knee pain, is runner's knee or walker's knee, known medically as chondromalacia patella or patello-femoral syndrome. This is caused by misalignment of the kneecap in its groove. The kneecap normally goes up and down in the groove as the knee flexes and straightens. If the kneecap is misaligned, it will pull off to one side and rub on the side of the groove. This causes both the cartilage on the side of the groove and the cartilage on the back of the kneecap to wear out. On occasion, fluid builds up and causes swelling in the knee.

      As a result, you will experience pain around the back of the kneecap or in the back of the knee after running. You also will have difficulty going up and down stairs and running hills. It will become painful to sit still for long periods with the knee bent. This is called the "theater sign" of runner's knee because people can't sit through an entire movie or play without getting up to move around. Half of the people you see outside their cars along the roadside are not going to the bathroom; they are stretching their legs to relieve the discomfort of runner's knee.

      The basis of the problem is not the knee but the foot. An inward roll of the foot and ankle causes the shin bone to rotate to the inside, which turns the knee to the inside as well. The kneecap ends up sliding at an angle instead of straight up and down.

      Treatment involves correcting the foot strike by propping up the foot with an arch or orthotic device inside the running shoe. This prevents excessive pronation and keeps the knee in alignment. I suggest you start with a commercial arch support and progress to a hand-made orthotic if you don't get suitable relief.

      You also need to do exercises to strengthen the inner side of the quadriceps muscle. The muscle in the front of the thigh hooks in the kneecap and helps align it into the center of the groove. Normally, you strengthen the quadriceps with the full Leg Extension described in Chapter 1. However, in runner's knee, as the quadriceps contracts, it pulls the kneecap back into the groove and grinds it against the side as you lift your calf. Therefore, you cannot do the full range of leg extensions with the knee bent without worsening your symptoms.

      There is a way to get around this. The inner side of the quadriceps muscle comes into play only in the last 30°, or six to eight inches, of a full leg extension. At this point the kneecap is up out of the groove. The idea is to work the quadriceps only within these last six to eight inches of the lift, as described in the 30° Leg Extension.

      If you are doing other leg-strengthening routines, stay away from leg presses or squats, which put stress on the bent knee. Bending the knee more than 30° will cause symptoms to flare up, so any kind of bent-leg exercise is bad.

      The same principle goes for riding a stationary bicycle. The seat should be high enough so that you bend your knee as little as possible. Avoid using a StairMaster® because climbing steps is particularly worrisome. A stepper that allows you to adjust the height of the step is acceptable if you use a very short step.

      A large dose of aspirin is helpful in stimulating the regeneration of cartilage in the kneecap. Take two plain or buffered aspirin pills with food or milk four times a day until your knee is better. If you have stomach problems, buffered aspirin is better than plain aspirin.


Inflammation of the tendons that hook into the upper and lower ends of the kneecap is called jumper's knee. Both of these tendons, the quadriceps and patellar tendons, help to straighten the leg. When these tendons are overstressed, they become inflamed. The sudden, violent vertical leap straightens out the knee, and may cause minute tears that irritate the tendons. It usually hurts more going up than coming down since you must exert a greater force to get up into the air.

      The treatment is to rest long enough to get over the acute pain. Anti-inflammatory agents may help reduce the pain. Then you can ice the knee intermittently for as long as it is tender. This will enable you to begin a weight-lifting program to strengthen the tendons and muscles.

      Use a leg extension exercise similar to the one described for runner's knee, but extend through the knee's full range of motion. The quadriceps controls the entire action of the knee, and that's the muscle you need to work on to tolerate the stress of jumping again. Leg curls are not as important, but it's a good idea to keep the balance between the hamstrings and the quadriceps muscles.

      The same strengthening program can also help prevent a recurrence by ensuring that the tendons are not overstressed.


Seen only in adolescents, Osgood-Schlatter disease is not really a disease but a syndrome. It was named before doctors fully understood what it was all about. It is an overuse syndrome related to the growth process.

      The lower end of the patellar tendon attaches to a knob on the surface of the tibia. As a child grows, this knob becomes larger to give the tendon more to attach to. The constant yanking on this tendon from running and jumping, which adolescents do a lot of, can cause some irritation in the knee.

      Every time the child with this syndrome straightens the leg, say, to go up stairs or ride a bicycle, the pain becomes worse. The dull ache may come and go, depending on how active the child is. However, the worse the syndrome gets, the more it hurts.

      Also, the knob becomes stimulated to grow and protrudes below the knee. The lump on the shin bone will be tender to the touch.

      Luckily, this is a self-limiting syndrome. It always disappears by age 17 in males and age 16 in females, when the knob stops growing. By then, the tendon is yanking on a solid piece of bone, and the pain goes away, although the protuberant knob will always be there.

      In the old days before sports medicine, children with Osgood-Schlatter's disease were banned from activity. They were put in a long leg cast for six weeks, which was cruel and unnecessary punishment. No one knew how long it took to heal, and the doctor couldn't detect healing through the cast. Worst of all, the leg muscles atrophied.

      Some old-time doctors still immobilize the leg. I still see a lot of despondent kids who have been told they can't compete for a year or two. In fact, there is no reason they can't return to full activity. Only those who have severe pain require a few weeks of rest.

      I don't stop young athletes from participating in sports until I hear them say, "It hurts too much. I don't want to play." As long as they are willing to put up with the discomfort, I let them play since there is no possibility of permanent damage to the knee.

      To keep a young athlete going, I prescribe ice after activity, aspirin or anti-inflammatories, and maybe short periods of rest for a few days. When the child finally says, "No more," I immobilize the knee with a splint, which prevents the knee from bending and the tendon from pulling on the knob. I leave the splint on until the knob no longer is tender to the touch, although the splint is taken off every day to allow the child to shower. When the knob doesn't hurt, the child is ready to return to action. This may take a few weeks or more.

      The pain may come back in a few weeks, months, or years, or it may never come back. Of all the kids I see, 99 percent get through Osgood-Schlatter disease without needing a knee splint. Most kids get by and continue to play. In addition to icing and anti-inflammatories, I recommend buying a good pair of basketball or wrestling knee pads. They should be worn low over the knob because hitting it is extremely painful and aggravates the syndrome.


Pain along the outer side of the knee is often due to iliotibial band syndrome, particularly among runners. The pain usually begins 10 to 20 minutes into the run and gets progressively worse until you are forced to stop. As soon as you stop running, the pain almost always goes away, and it won't bother you again until your next run. Ten to 15 minutes into the run, the pain comes back and intensifies the more you run. If the condition persists, the pain will come on earlier and earlier into your run.

      The cause of the pain is an overly tight iliotibial band. This is the hard band of fiber at the outside of the thigh extending down to the knee. The band starts at the rim of the pelvis, crosses the point of the hip, comes down the thigh across the outer side of the knee, and attaches below the knee. It helps keep the hip from moving too far to the outside, sort of like the check rein you see on the outside of a racehorse's leg.

      Sometimes the band overdevelops and tightens with exercise. When you run, the band saws against the bony ridge on the outside of the knee as you bend and straighten your leg. It rubs hard enough to irritate the knee and may cause similar pain over the point of the hip.

      Treatment is quite easy: All you need to do is stretch the band (see the Knee-over-Leg Stretch [Iliotibial Band Stretch] in the stretching program in Chapter 1). You will feel discomfort or pain in the buttock area right behind the bony prominence of the hip due to the band stretching.

      Since the band is all one piece, stretching it in the upper part will loosen it all the way down, and you will no longer feel pressure against the side of the knee. Do three repetitions of the Kneeover-Leg Stretch, holding for 20 to 30 seconds. Do this five or six times a day until you can feel that the band is loose and it no longer causes pain during a run. This stretch should become part of your daily routine. If the pain is not better in 10 to 14 days, see a doctor.


Osteoarthritis is the wear-and-tear degeneration of the knee. Spurs of bone form along the edges of the knee joint and wear down the cartilage. This can be aggravated by an injury to the knee. Also, bowlegged people may develop severe osteoarthritis of the knee because the bowing causes increased pressure of the inner part of the tibia against the medial femoral condyle. This wears out the inner cartilage and causes bone to grate on bone, leading to arthritis.

      Bone spurs or pieces of worn-down cartilage can break off and float around in the knee. This causes pain during activity and swelling of the joint. Anti-inflammatory agents will help ease the pain. If an x-ray reveals that you have a large amount of debris in the knee, arthroscopic surgery can clean out the joint and provide relief for up to a few years. Then your knee may need to be cleaned out again.

      If the pain becomes so severe that it interferes with activity, the knee may have to be replaced with an artificial joint.


A large sac of fluid may form in the front of the kneecap due to a sudden blow or trauma to the knee. The medical term for this condition is pre-patellar bursitis. Common among roofers, floorers, and carpet layers, who work on their knees, this used to be called "housemaid's knee," a reference to maids scrubbing floors on their knees.

      Trauma to a bursal sac in front of the kneecap irritates the kneecap and causes fluid to form in the sac. Treatment is drainage of the bursal sac with a needle, and then injection of cortisone into the sac if it continues to fill with fluid. If the condition persists and can't be controlled with cortisone, the sac must then be removed surgically.

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