LOCKING
There are two types of locking, true locking and pseudo-locking. More precisely, there’s what your doctor would call locking and what you would describe as locking.
True Locking
For the orthopedist, true locking doesn’t mean that the knee can’t be moved, but rather that something is preventing it from fully straightening out. It’s like trying to close a door that’s wedged open. Whatever it is that’s wedged in there may slide out of the way (only to remind you of its presence by sliding back again when you least expect it) or it may be a source of continuing trauma.
The key to locking is often a torn cartilage or a loose body (such as a bone chip) that has finally been caught and it has grabbed your attention. The locking of a meniscus, at least on the first occasion, generally occurs while doing something active, like playing football. A loose body lock is more likely to occur during an everyday activity, such as walking downstairs.
“How come l have this torn cartilage and it locked on me and I've never had a major injury?” I hear patients complain. If pressed, some do recall some sort of injury, maybe twenty years ago, but it was “no big deal.” That loose body in your knee may have been off to the side, with everything functioning fine, until that one additional maneuver gave it just enough freedom to ‘get caught. Or perhaps there truly was no one traumatic incident that initiated the whole process. Imagine a carpenter who is constantly squatting. For whatever reason, every time this carpenter squats there is a tear of his cartilage, microscopic at first, then after two years it’s a millimeter wide, another two years and another millimeter of tear, and finally one day it rips completely.
If the problem is a loose body sailing around the synovial sea, it probably started off as a small bone chip that broke loose during a moment of trauma. They range from sand size to as large as a quarter. Of course the body doesn’t like UFO’s (Unidentified Floating Objects), so it tries to break them down and reabsorb them. If that doesn’t work, it tries to wall the intruder off by laying down scar tissue, or it may start laying calcium over it. In either case the end result is felt as a locking sensation or a “giving way” of the knee.
To alleviate true locking, the fragment must be removed, whether it’s a bone chip or a torn meniscus. Otherwise there will be subsequent damage as the fragment continues to wedge itself into the bones of the knee. Fortunately, bothersome pieces of cartilage can easily be removed by a surgical technique called arthroscopy.
Some people have tried rest, elevation, and anti-inflammatories in an attempt to lesson the swelling that sometimes accompanies locking. Occasionally this allows the fragment to slide back into place. Others have also tried twisting or manipulating the leg. However, the best answer is still a surgical one.
Pseudo-locking
The second type, which I call pseudo-locking, is what a lot of people call locking when certain movements simply hurt too much to do. The knee may not be incapable of complete movement, but there is an area of exposed surface within the knee. When that surface bumps up against another surface there is pain and discomfort, which discourages you from extending your knee all the way.
So you tell your doctor your knee is locked and you can’t straighten your leg out all the way. You say, “My knee locked while going down a flight of stairs. There was this sharp pain and then I couldn’t move it.” I say, “But can you move it if you try?” “Yes,” you say, “but it hurts.” What is actually happening is that when your knee hits a particular angle or feels a certain pressure, it hits the panic button, triggering protective muscle function and a string of internal expletives.
The most common cause is damage to the knee surface, generally chondromalacia patella or osteoarthritis. You will likely have a history of grating within the knee if you develop pseudo-locking. You’re also a likely victim of a subluxating or dislocating patella. Swelling, however, is not common.
For pseudo-locking the best treatment is rest, which allows the area of irritation to heal and then regain its movement and strength. So if you suffer from an episode of pseudo-locking, relax. Get off your feet for a few minutes. Usually you’ll be able to move again- gently—after a few minutes. A cold pack while you’re resting may also help.
GIVING WAY
Sometimes a knee doesn’t lock, but it does give way for a moment, giving the owner a bit of a stop. When I was growing up in the Midwest l had an electric train. If it went over an imperfect junction it would bounce off the edge and bump right back onto the track. Like my Lionel train, the knee has three tracks. One holds
the kneecap (or patella). lf, for some reason, the kneecap doesn’t stay in its track and subluxates (slips out) for a moment, your thigh‘ muscles lose control. That’s instability. If one of my Lincoln logs fell across my train track, it would derail. A loose body along the general track of your knee probably won’t derail you, but you’ll know you’ve hit a bump. And the third track is made up of your ligaments. Perhaps they’ve been damaged by injury or become stretched out. The forces of movement may be too much for them to handle and they give way. All of these would come under the general diagnosis of patella subluxation or dislocation.
Another possibility is that the muscles that control the knee are weak and unstable; perhaps there was a previous injury and they have not been properly rehabilitated. If the muscles lose control for a moment, you feel them give way and you instinctively reach for support or prepare for a fall.
Giving way due to an old ligament injury, muscle instability, or the locking of a loose body frequently occurs while descending stairs or jumping from a height. If the problem is a torn cartilage, the triggering event is often a rotary movement, such as turning round suddenly, stepping on a small stone, or walking on uneven
ground.
SNAP, CRACKLE, POP
Perhaps the most common concern expressed about the knee comes from people who worry about the snap, crackle, and pop that comes with activity. They fear that their knees are deteriorating right before their very ears. For the most part, as long as there is no accompanying pain, an occasional grumble from the knee should not be of major concern. In fact, considering what the joint is forced to put up with over the course of daily living, it’s not all that surprising that most people over the age of twenty manage to hear at least some knee noise.
Generally, such sounds can be traced to tiny bits of cartilage that have chipped away from bone and gone floating off into the synovial sea. When the joint moves, the chip passes between the intact cartilage and makes a popping sound. Usually, this is not painful and does not damage the joint. It just makes it tricky to
sneak up on people.
When large pieces of cartilage have broken off, however, they may actually chip away more protective cartilage as they go popping around the knee. And if a large piece wedges itself between the bones, the knee may suddenly lock.
How can you tell if the sounds you hear are just normal Rice Krispies or something more serious? Sometimes it’s difficult. lf you’re concemed about it, see your orthopedic specialist. However, the rule of thumb (or knee) is that you’re safe as long as there is no accompanying pain, swelling, or loss of function. For example, if you can’t sit for a normal length of time without pain, that would indicate a loss of function. (That’s what the British call “the theater sign.”) If you have poorly localized knee pain, which is exacerbated
by going down stairs and hills, that also could indicate a more serious problem. Again, when in doubt, ask a specialist.
Most commonly heard is an occasional click, which is fairly universal and represents nothing very significant. Too many clicks, however, equal a creak, and you don’t want to be up a creek without a diagnosis. So if you’re worried, check in for a checkup.
The most common cause of all this noise is chondromalacia patella, which results from trauma. A subluxating or dislocating patella is also a possibility, with traumatic and degenerative arthritis a less likely competitor in the snap, crackle, pop diagnostic derby.
A snap or pop (which is not accompanied by a traumatic event) could represent something sliding over the joint, such as a torn cartilage or a loose fragment. It could also be the kneecap snapping or popping along (or out of) its track.
Crackling, grating, or grinding is most worrisome. That is called crepitation, and it means that there is a roughness to a surface and you’re hearing bone rubbing against bone or roughened cartilage. That’s a much more ominous sign of degeneration of a joint surface.
PAIN AND TENDERNESS
Pain may be caused by swelling, nerve fibers that have become torn or irritated, or degenerative changes, most often associated with arthritis. If you can accurately locate the site of the pain, it will greatly assist the doctor in making the diagnosis. Of course if you happen to be a procrastinator, it’s best to remember where the pain was felt first. '
The location of the pain, the severity of the pain, and what makes the pain occur all offer clues to the underlying problem. For example, a low-grade aching pain on the front of the knee occurring during hill climbing most likely represents chondromalacia patella. The same pain may also appear in the middle of physical activity and the same patella problem is probably at fault. (For more information concerning this and other specific complaints.)
Such low-grade pain often begins after activity, but if you persist in these activities, the pain becomes sharper and more persistent. lf left untreated, the pain may eventually force you to severely restrict your activity. Besides chondromalacia patella, this type of pain is symptomatic with tendinitis, patellar tendinitis, or stress fractures on the front of the knee and iliotibial band friction syndrome on the outer side of the knee or bursitis on the inner side.
Another classic pain is often quite sharp and associated with a tearing sensation, swelling, and instability, all brought about thanks to a fall or twisting maneuver deep within the knee. Such moves can cause either ligament or meniscal damage. The mode of injury is often an athlete attempting to change direction quickly. lf there is an audible “Pop!” upon injury, the problem is likely to be a torn anterior cruciate ligament. lf the pain occurs on either side of the knee, then the injury is suggestive of a medial (inner) or lateral (outer) ligament or meniscus tear.
PUTTING IT ALL TOGETHER
Let’s take an example and look at what happens to a knee, and to add some drama to the script, let’s say your first response is to ignore the problem. (Sound at all familiar?) Your foot is planted and you make a sudden turn. No big deal, a little swelling perhaps. But a part of your meniscus has tom and it’s caught there between the inner edge of your femur and tibia. You continue to walk on it, trying to force the knee closed with every step. Your knee says,
“This is stupid. If that’s the way you’re going to be, all I can do is pour out more lubricant and at least try to minimize the damage,” and the swelling increases. You’ve still got that fragment wedged in there, and now the meniscus is starting to atrophy because you keep grinding away at it. At the same time the fragment is starting
to wear a groove in the bone surface, setting the stage for an arthritic condition, an inflammation, or effusion of the joint.
Pain is now more diffuse and you can’t put your finger on the source. (Of course by now it’s so tender you probably don’t want to touch it anyway.) The muscles controlling the knee attempt to protect the injury by going into spasm and preventing the normal arc of movement. Unable to move through their natural range, the muscles start to atrophy. So now you’ve got muscle weakness, a locked knee that probably gives way with increasing frequency, swelling of the knee, more pain than you care to think about, you’re startingto scratch and damage the surface of the joint, and somewhere, from deep inside, comes an inclination to call a doctor.
Perhaps half of the pain of a traumatic injury is due to accompanying muscle spasms. In a spasm the muscles surrounding the injured part vigorously contract and hold that position——sometimes for days. While such spasms are intensely painful, they’re actually the body’s way of protecting itself from further injury. Think of it as a built-in splint, immobilizing the damaged part much like a cast
immobilizes a broken leg.
Too often, pain is ignored or blunted with medication. This is an Invitation to reinjury or even greater injury. When it comes to pain, the individual who self-medicates has a fool for a doctor. If pain persists after two days of self-medication, see your doctor.
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