Rehabilitation for the Extensor Mechanism
Recovery from an extensor mechanism problem requires a disciplined rehabilitation program. Proper exercise selection and correct exercise technique can relieve knee pain and prevent further problems. Once the problem is diagnosed, a physical therapist will select an exercise program and teach you how to perform these exercises at home.
The main goal of rehabilitation is to strengthen the extensor mechanism, especially the vastus medialis obliquus (VMO) muscle that helps stabilize your patella (knee cap). If the VMO is not strong enough, it gets overpowered by the much larger vastus lateralis muscle. Initial exercises include quadriceps sets and straight-leg raises (Fig. 1,2). For some (but not all) extensor mechanism problems, a patient may gradually progress to mini squats and side step-ups (Fig. 3,4). Knee extension machines must be avoided because they increase compressive loading on the patellofemoral joint, causing damage to the extensor mechanism.
It is also important to know that what is happening at the front of the knee (the extensor mechanism) is affected by what is happening above the knee at the hip joint, behind the knee, and below the knee at the foot. The hip muscles, especially the hip abductors, stabilize the pelvis when you walk. If these muscles are weak, then increased stress is placed on your knee. Performing hip abductor strengthening exercises can prevent this from occurring (Fig. 5).
The bottom of your foot is supported by many muscles. Weakness of certain foot muscles, such as the posterior tibialis, can affect the way you walk, placing stress on your knee. Strengthening exercises for the posterior tibialis can improve the way you walk and take stress off your knee (Fig. 6).
The hamstring and calf muscles cross the back of your knee. If they are tight, the extensor mechanism must work harder to straighten the knee. This can cause tightness in your knee while walking or running. Or you may experience aching while you are sitting or resting after these activities. Hamstring and calf-stretching exercises are very important and will help with this problem (Fig. 7).
Strengthening exercises should be performed in three to eight sets of ten, three times per day (certain restrictions may apply depending upon your age and activity level). Low resistance (lifting only the weight of your leg and progressing to no more than a few pounds) and high repetitions (multiple sets of ten) are recommended. Stretching exercises should be performed in sets of five, three times per day, holding each stretch for 30 seconds.
All exercises must be pain free. The expression "NO PAIN, NO GAIN" does not apply to rehabilitation of the extensor mechanism. If you do have pain, you should first make sure you are using the correct technique. If you feel that your technique is not the problem, or if you are not sure that your technique is correct, you should consult with your physical therapist.
Swelling of the knee should be monitored and controlled with rest, ice, compression, and elevation. Fluid buildup in the knee can prevent the quadriceps muscle (especially the VMO) from working properly. In addition, you must be diligent with your rehabilitation exercises. If you are not, your knee may continue to swell and be painful, and your extensor mechanism will remain irritated.
It takes a lot of effort and patience to comply with a disciplined extensor mechanism rehabilitation program, but the end result is well worth it!
Teri L. Mingee, M.S., P.T.