Overuse Injuries of the Knee: Chondromalacia Patellae or Runner's Knee

In 1972, Dr. George Sheehan wrote about chondromalacia in runners in the American College of Sports Medicine Newsletter. Two years Later, Dr. Steven Subotnick, a podiatrist from California, wrote a preliminary report on runner's knee. A short time later at a Podiatric Sports Medicine Seminar, Dr. Sheehan presented a lecture entitled "How to Treat Runner's Knee". In his lecture he began by saying, "I am not going to keep you in suspense; you treat the foot!"

Much has been learned in the past few years regarding knee injuries in athletes and specifically in runners. Let me state clearly at the onset that my comments are restricted to only overuse injuries of the knee and not to traumatic problems. If there is a history of an injury with the classic signs of swelling, restriction or loss of motion, locking or giving way of the knee, it is important that an examination be performed by an orthopedist.

Statistically, forty-two percent of the runners we see as patients in our office present them selves with some type of knee discomfort. Almost all these are related to an overuse problem caused by abnormal foot and leg mechanics and/or leg length discrepancy. In general, problems on the inside of the knee are related to proration (flat foot conditions) and those on the outside of the knee from supination (high arched foot conditions). Knee discomfort is usually seen with an abnormal foot type in combination with a leg length discrepancy, muscular imbalance or structural malalignment. Overuse injuries to the knee are defined as any injury occurring around the knee joint caused by repetitive microtrauma from participation in normal sports. The key word here is repetitive. Generally the knee conditions are described either as runner's knee or chondromalacia, jumper's knee, tennis knee or hiker's knee.

Anatomy of the Knee
While the anatomy of the knee joint is complex, a basic review of its functional components is necessary in the understanding of overuse syndromes. Dr. Harry Hlavac, author of The Foot Book, provides a rather clear explanation. The knee joint is primarily made up of two bones, the thigh bone or femur and the larger of the leg bones, the tibia. The femur ends in two ball ends, condyles side by side and the tibial counterpart consists of two sockets side by side. They are cushioned by joint fluid and specialized cartilage, the medial and lateral meniscus. Motions occur essentially in one direction. When forces are placed on the knee in other directions, then injuries to the supporting soft tissues can occur. These soft tissues are more for secondary stabilization than for primary support of the knee. Knee stability is primarily accomplished by the quadriceps muscles in the front of the thigh bone. These four muscles insert into the patella or knee cap which then inserts into the tibia via a strong tendon called the patella tendon.

The knee cap increases the efficiency of the quadriceps muscle as it crosses the knee joint. The knee cap is involved in a variety of overuse in juries. The quadriceps muscles function to extend the knee joint, and the hamstring muscles on the back of the thigh function in knee flexion. Both of these muscle groups help to prevent twisting motion of the knee. Other muscles on the inside and outside of the knee joint also help to keep the joint in proper alignment by the force that they exert when crossing the knee joint.

The knee ligaments are very strong and help prevent sideways motion. A specialized ligament called the ilio-tibial band extends down from the hip on the outside of the thigh and inserts across the knee joint. There are also ligaments inside the knee that prevent forward and backward dislocation of the joint. Like the menisci, these ligaments are seldom involved in overuse injuries. Most knees are normal, but after continued abnormal stress they are subject to deterioration and fatigue.

In normal running there are approximately 180 foot strikes per minute. If one runs for an hour this results in 5,000 foot strikes on each foot. Therefore, when confronted with an overuse in jury of the knee, we look to the foot and its function as well as the actual site of the injury. In other words, the knee discomfort experience is secondary; that is, it is a symptom and not usually the cause of the problem.

Causes
Runner's knee, commonly known as chondromalacia of the patella, is a condition where the cartilage under the knee cap becomes overly worn as the knee cap moves abnormally. There is a direct relationship between abnormal internal leg and thigh rotation and abnormal knee cap functioning.

This is most always secondary to abnormal foot function. As the foot prorates at heel contact and throughout stance phase the leg rotates inwardly. The knee cap however does not internally rotate with the leg. Instead it rides over the lateral aspect of the femur. Abnormal thigh and leg structure as well as poor running habits, like overstriding appear to be involved also in runner's knee.

We test for chondromalacia by pressing on the knee cap and feeling for a grating or grinding sensation as we move the knee cap backwards and forwards. There may also be stiffness around the knee after periods of rest. Chondromalacia more likely develops on a leg that goes through an excessive internal rotation due to increased foot proration. This increases the angle of pull of the quadriceps which in turn pulls the knee cap laterally leading to erosion on its undersurface. This Q angle formed by the pull of the quadriceps is increased in a prorated foot.

Once underway, no treatment short of correcting the foot abnormality will help. Anything else is symptomatic. Pain and swelling which can occur beneath or along the knee cap will subside, but as soon as the running resumes the pain will return.

Treatment
Treatment is directed not only at the symptoms but at the cause of the problem. Most runners that I see have knee problems that are not so symptomatic that they cannot run. Following an examination, they are usually fitted with a temporary orthotic insert with rear and forefoot controls and a leg length lift, if necessary, and instructed to continue running. It may be necessary to reduce their existing training schedule. It is also recommended to avoid speed work and running on hills. In addition, anti-inflammatories, combined with strengthening exercises of the quadriceps are utilized.

My preference, however, is not to in any way interfere with my biomechanical approach to the knee condition. The temporary orthotic inserts are used to diagnose whether the knee discomfort will respond to biomechanical control and allows for adjustments to be made in the device before a permanent orthotic might be used.

Biomechanical abnormalities are not always the direct cause for knee problems. Poor fitting shoes that allow for abnormal foot function and excessive rotation of the leg can be a causative factor, as well as running on undulating surfaces such as grass, roads, or beaches that are excessively banked.

Pain in and around the knee is the most common complaint among runners. This discomfort is related to an imbalance in the foot and leg that secondarily affects the knee. As the foot has to compensate, the angle of the quadriceps muscle is increased which pulls the knee cap laterally and produces symptoms. An orthotic device or other mechanical method including over-the counter support tends to reduce the angle and the ensuing knee pain.

Women appear to suffer more from this type of problem because of a wider hip structure as well as more pronounced knock-kneed type angulation with a result in increase in the quadricep angle. Lateral knee discomfort is frequently seen in runners with a foot structure that lacks shock absorbing properties. The stress is transmitted to the knee. Orthotics usually can help dampen some of the impact shock and therefore lessen the knee discomfort.

Conventional medical care dictates treatments consisting of stopping the activity, taking some kind of medication, being injected with a steroid, or going in and taking a look around (surgery). Podiatrists can effectively keep most patients running without risks of injury by careful biomechanical evaluation and treatment for their functional knee problems. An article by Hal Hig don in Runner's World entitled "Getting to the Foot of the Problem" says it all. He states "It may sound like an oversimplification, but most running injuries stem from the foot."