chapter 7: nonarthritic anterior knee pain
REHABILITATION OF SOFT TISSUE PROBLEMS
Before an appropriate rehabilitation program can be formulated, one must identify the specific source of pain. In those patients with predominantly soft tissue pain related to malalignment, conservative rehabilitation is usually effective (36 38). Quadriceps strengthening has been a central component of rehabilitation in the patient with patellar malalignment. Some of the pain relief after quadriceps strengthening may be related to altered soft tissue balance around the patella.
The program of extensor mechanism rehabilitation should avoid high impact loading activities in case there is associated articular disease (39). Grood et al (40) noted that very large quadriceps forces are needed to raise a 7 lb weight through a range of motion, and that the last 15 degrees of knee extension causes particularly high quadriceps force. Consequently, Grood et al (40) recommended exercise in the 15 to 50 degree range to avoid quadriceps stress. Because patellar contact stress is ordinarily greatest at 65 degrees of knee flexion, exercise at lesser degrees of knee flexion is desirable, and terminal extension exercises will maximize quadriceps demand (and thereby strengthening). The vector of quadriceps pull at 0 to 15 degrees of knee motion is such that there is little increased patellar articular load, despite maximal quadriceps stress.
Recently, Steinkamp et al (41) have demonstrated that leg press exercise creates lower patellofemoral stress in the 30 to 0 degree range of motion when compared with knee extension exercise, the reverse being true in 60 to 90 degree range of motion. The type of exercise selected, therefore, should be specific to the pain free range of motion.
Miller et al (42) noted that a program of isometric quadriceps exercises over a period of 3 months resulted in increased vastus lateralis and vastus medialis obliquus (VMO) activity without any notable alteration of muscle balance. On this basis, Miller recommended selective training of the VMO. Nonimpact loading during exercise may be accomplished through stationary cycling, swimming, isometric exercises, and activities such as cross country skiing and running. Ericson and Nissell (43) noted that patellofemoral compressive force was approximately 1.3 times body weight when cycling at midlevel saddle height and 60 rpm. In general, for stationary bicycling, the seat should be set somewhat higher such that the knee is extended to 15 degrees during exercise. Biofeedback and electrical stimulation may be used selectively to help in building VMO strength. Isokinetic exercise is not usually necessary or even desirable in the rehabilitation of most patellofemoral pain patients, but objective quadriceps strength gain should be documented by isokinetic testing to confirm that the patient has made an adequate effort. Isokinetic testing, however, can cause dangerous increases in patellar articular load and must be used cautiously. Certainly, patients who do not exhibit reasonable motivation in their rehabilitation are not patients who should be considered for surgery in most cases.
Braces may be helpful in the management of patients with patellofemoral pain of either soft tissue or articular origin (Figure 7.7). The Trupull wrap brace is extremely versatile and may be wrapped by each therapist or patient to address a specific painful area. For instance, patients can rotate the pad beneath the patella for patellar tendonitis and wrap it either tighter or looser as needed.
Lysholm et al (44) noted that 88% of patients improved their performance on a Cybex isokinetic dynamometer when a patellar brace was used to treat patellofemoral arthralgia. Moller and Krebs (45) found similar symptomatic improvement of patellofemoral pain patients using patellar braces. Simple elastic sleeves with a patellar cutout and Levine straps can be very helpful in symptomatic management and may cause slight alterations in soft tissue tensions, thereby giving relief, but not causing any major alteration of patellar tracking. Osternig and Robertson (46) have pointed out that prophylactic knee bracing can actually alter neuromuscular control around the joint. This suggests that true modification of patellar tracking may occur with brace use.
McConnell (47) has reported good success in patellofemoral pain patients using specific muscle strengthening and taping techniques to modify patellar tracking. This innovative approach warrants further investigation, because it appears to be helpful in the management of retinacular and articular pain problems related to patellar malalignment (Fig. 7.8). The findings of Osternig and Robertson may apply here also. Although it does not appear that patellar tape actually changes patellar tracking mechanically to any significant degree, neuromuscular proprioceptive responses to tape only create true functional improvement of patellofemoral function. There is little doubt that these techniques benefit patients.
Nonsteroidal anti inflammatory medication has been somewhat helpful in roughly half of all patients with patellofemoral pain (48). Although nonsteroidal anti inflammatory medications are not always helpful, they are worth considering if there is specific evidence of inflammation, persistent effusion, or need for pain management.
Some patients with anterior knee pain demonstrate a significant abnormality of gait either while walking or running. James et al (34), McKenzie et al (49), and others have noted that appropriate footwear and selective use of orthotics may be helpful in the patient with anterior knee pain. In our experience, inexpensive off the shelf orthotics are frequently helpful in such patients, particularly if there is significant pronation. Expensive, custom orthotics are less frequently necessary when more complex lower extremity alignment problems exist and when the amount of wear, because of extensive athletic participation, requires a permanent orthosis. It is our impression, however, that off the shelf orthotics made of cork and leather or materials such as sorbothane are preferable to highly rigid orthotics, in many cases.
In addition to the benefits of specific strengthening (50), physical activity can enhance self esteem and help in the return of patients with anterior knee pain to improved levels of function. The rehabilitation program must be based on a thorough examination and understanding of each patient, with awareness of the peripatellar structures as well as the patella itself (51). A well structured exercise program using a Trupull wrap, and emphasizing activities that do not create excessive contact stress on the patella, should therefore should remain be the cornerstone of any good patellofemoral rehabilitation program.
Inside Chapter 7: