Dirt Rag Magazine

Blast From the Past: Knee Owner’s Manual

Editor’s note: This article first appeared in Dirt Rag Issue #135, published in May 2008. Words by David Alden-St.Pierre, MS, PA-C. Medical illustrations by Kerry Nicholson.


As a mountain biker, at some point in your life, you’re going to have some knee pain. In fact, mountain biking and grinding, creaking, cracking, crunching knees almost go hand in hand.

According to Dr. Ira Evans III, a successful Massachusetts orthopedic surgeon and a mountain biker, most of that is due to training errors, poor biomechanics, overuse, poor bike fit or inherent anatomical variations. Let’s get more into the causes behind knee pain and what you can do about it.

knee-owners-muscle

Knees 101

“The knee consists of bone, ligaments and cartilage which work in unison to provide a complex roll and glide motion resulting in a stable joint with a wide range of flexion and extension,” explains Dr. Evans.

Technically, your knee is the joint that joins the femur (thigh bone) and the tibia (shin bone). The patella floats in front of the two bones, and acts as a pulley to give leverage to, and increase the power of, the four quadriceps muscles, which straighten the knee. Your quads come together at the patella, and a single tendon extends from the patella to the tibia.

The three hamstring muscles in the back of the thigh handle just about all of the knee-bending that occurs at the joint, although sometimes other muscles do help. Strong ligaments on both sides of the knee (the LCL and MCL) keep it from flexing out to either side, and a pair of ligaments that criss-cross inside the joint (the ACL and PCL) also help with stability. Two large pads of cartilage (medial and lateral meniscus) sit atop the tibia and act as shock absorbers, and the whole joint is wrapped in a membrane called a synovial joint capsule.

“It is the complexity of this anatomy, and its inner workings, that put the knee at risk from even very simple disturbances,” says Evans.

knee-owners-bone-1

Figuring Out What’s Wrong

Injuries that result from crashes or other obvious problems are often easy to diagnose and recover from. But what about that random nagging pain that seems to only show up after an hour of riding? Or that grinding that you feel the day after a race? These problems might be harder to pinpoint.

“When assessing a rider with a knee injury,” says Evan, “it is important to perform a thorough knee exam, but it is even more important to look for subtle predisposing factors.” He adds that your limb alignment, limb rotation in both the femur and tibia, foot rotation, and leg lengths should also be evaluated.

“Cyclists with excessive rotation in the tibia (external tibial torsion), varus alignment (bowlegs), flat feet (hyperpronation) and/or significant leg length discrepancies may be predisposed to problems,” explains Evans, “and these problems should be addressed at the same time that the knee injury is being managed.”

Other problems can arise from differences in strength and/or flexibility in the muscles that control the knee. If an area is tight, it can pull the joint out of alignment, causing excessive wear. Women, in particular, can be afflicted with problems that affect the way that their patella tracks in its groove.

And, you could have perfect anatomy but poor form, meaning you mash the pedals instead of pedaling with a smooth cadence, or you pedal with your knees flaring out to the side. Correcting that can often help eliminate minor aches and pains.

Diagnosing a knee problem can be difficult, and we certainly don’t want you to try to do it yourself. However, Dr. Evans has provided some of the more common problems, which are presented in the sidebar.

You Knee-d Proper Bike Fitting

One important area of possible problems is your bike fit, including pedal cleat type and position, plus saddle height and fore/aft position.

“Excessive internal rotation of a rigid cleat or a cleat too far forward can cause ITBS [see sidebar],” says Evans, “and simply switching from a fixed to a floating pedal system or making small adjustments in floating cleat position may be all it takes.”

A saddle height that is too high, causing knee extension greater than 150°, or a saddle position that is too far back, which increases pedal reach and over-extension at the knee, can also lead to ITBS. On the other hand, a saddle height that’s too low can cause excessive force on the patella resulting in pain in the front of the knee.

As you can see, getting your fit just right can be critical. Many bike shops offer fitting services, but they are not all at the same level. A bike shop “fitting” can range from a shop employee telling you what size frame is right for you, to an hour-long process of measuring and fitting by a trained employee that can cost upwards of $100.

If you have knee problems, try to find the most qualified person—one with a working knowledge of anatomy. Physical therapists, licensed cycling coaches and Serotta-trained shop employees are a good starting place.

“In most cases you don’t need a customized bike to minimize your risk of injury as long as the bike is sized and adjusted correctly,” adds Evans.

On the Trail to Recovery

“The management of a knee injury often includes decreasing mileage, riding on flatter terrain, and lowering workout intensity by pedaling easier at a lower, pain-free resistance,” says Evans. He adds that occasionally the use of a formal physical therapist is indicated to correct strength or flexibility deficiencies and to incorporate additional therapies such as ultrasound, electrical stimulation and friction massage. Also, the use of an anti-inflammatory medication as directed by your doctor is often helpful.

In some cases however, surgical interventions are the best ways to get back to pain-free riding. Surgeons can remove torn pieces of cartilage, replace torn ligaments, re-attach muscle to tendon and smooth rough bone surfaces. Many times surgery only requires two or three small holes in the skin.

But don’t worry; most knee problems are minor, even though there may be multiple factors behind the pain. Just remember, the knee is designed to work in an up and down motion, like the piston of a car, and the slightest disturbance of that motion is amplified because with an average pedaling cadence of 80 revolutions per minute, each knee bends an average of nearly 10,000 times in a two-hour ride.

Play it safe, listen to your body, and get checked out if a problem persists. Occasional soreness and aching may be inevitable, but serious problems are not.

Sidebar

If you are having problems, or should we say, “when you have knee problems,” it will be helpful to give your doctor as much information as possible to help him or her with the diagnosis.

Dr. Evans suggests bringing the following information if you are having a knee assessment:

  • Information on any prior injuries, surgeries and/or therapies
  • History and timeline for the onset of pain
  • History of training practices (hills, time-trials, average mileage, cadence, intensity)
  • Information on how the symptoms relate to pedaling
  • The type of pain (sharp, dull, ache, jabbing, grinding)
  • The exact location of the pain

Anterior knee pain or pain on the front of the knee is quite common, and the patella is most frequently the culprit. Overload of the patella will result in pain, post-activity ache and a sense of instability and/or locking. There may be associated grinding or swelling. Inflammation of the patellar tendon or quadriceps tendon should also be considered.

Pain on the outside or lateral side of the knee is most commonly caused by iliotibial band syndrome (ITBS). The IT band is a broad band of tissue on the outside of the knee that can rub across the lateral side (outer side) of the femur causing inflammation. Recent studies have documented up to 24 percent of cyclists with this problem. Symptoms include pain and burning, and the rider may feel snapping, a gritty sensation and swelling. This syndrome has to be differentiated from a torn meniscus or cartilage, tendonitis or kneecap (patella) overload.

Medial knee pain (pain on the inside of the knee) is a complaint in about 20-60 percent of riders (depending on the study). The most common diagnosis is plica syndrome. A plica is a fold of synovium (the lining of the joint) that is a remnant of membranes that form the knee. It is normally not a problem but it can become inflamed with strenuous, repetitive exercise as it rubs over the side of the femur. The rider will have pain, and often times there will be some swelling. There may also be snapping, popping, grinding and tenderness over the band of tissue. Other considerations include a torn meniscus or cartilage and patellar problems.

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