chapter 12: Nonoperative Treatment
Strengthening the entire kinetic chain will benefit the patient with anterior knee pain. Although specific emphasis on quadriceps strength, particularly the vastus medialis obliquus (VMO) (Fig. 12.13), is logical in improving support for the patella, balance of strength is equally important. Therefore, isolated quadriceps strengthening is less effective than balanced strengthening of both lower extremities (Fig. 12.14). Steinkamp et al (15) have noted that leg press exercise (Fig. 12.15) from 0 to 30 degrees of knee flexion will diminish the knee moment and patellofemoral joint reaction force as well as patellofemoral stress when compared with knee extension exercise (Fig. 12.16). Therefore, leg press exercise, emphasizing high repetition and reduced weight, is most logical in the 0‑ to 30‑degree range of motion.
Nonetheless, at 60 to 90 degrees of knee flexion, patellofemoral joint stress is greater using leg‑press exercise, according to Steinkamp. Consequently, the therapist must adapt the strengthening program depending on the degree of knee flexion at which exercise is accomplished. The rule of thumb is, leg press exercise in early knee flexion and leg extension exercise past 60 degrees of knee flexion. This is particularly important since patients with lesions more distal on the patella will need to exercise in more knee flexion to reduce contact stress on the distal patella (which occurs predominantly in early knee flexion; see Chapter 2 on Biomechanics). For the patient who has had a crush-type injury to the anterior knee (such as the dashboard‑type injury), exercise will be safer closer to full extension, where the proximal crushed portion of the patella does not experience contact. Leg press exercise in 0‑ to 30‑degree knee range of motion is most appropriate here. The level of articular lesion is the single greatest factor in determining the degree of flexion in which exercises should be carried out.
Isometric quadriceps strengthening can also be highly effective. O'Neill et al (16) noted that patients with anatomically normal lower extremity alignment and no history of knee trauma or surgery responded favorably to isometric quadriceps strengthening as part of a structured exercise program in the treatment of anterior knee pain.
Ingersoll and Knight (17) emphasized the importance of VMO strengthening. Electromyographic (EMG) biofeedback training (Fig. 12.17) to selectively strengthen the VMO was effective in improving the patellofemoral congruence angle in their experience.
Work on timing of quadriceps contraction, emphasizing VMO contraction earlier in the gait cycle to stabilize the patella, makes sense. Electrical stimulation of the VMO and biofeedback training to incorporate earlier VMO contraction and sustained contraction during the gait cycle should be a part of any complete patellofemoral rehabilitation program. It is interesting to note, however, that no difference in EMG patterns of quadriceps contraction in female runners with patellofemoral pain was noted by MacIntyre and Robertson (18). Nonetheless, emphasis on earlier VMO contraction is logical and may help to compensate for minor malalignment of the extensor mechanism.
General strengthening of other muscle groups around the knee should be introduced to balance quadriceps power and flexibility. Maintaining a normal hamstring‑quadriceps ratio of approximately 65% is desirable. Much of this muscle balancing may be accomplished through closed‑chain exercises and through the aerobic conditioning part of the rehabilitation process.
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