ACL REHABILITATION

the patella tendon autograft, though there are an increasing number of quadru- pled semitendinosus/gracilis autografts being carried out. There are strengths and weakness when using either method, research studies have failed to show sta- tistically significant differences in terms of knee stability or functional outcome between either of the two methods.

Rehabilitation from ACL reconstruction There has been much discussion over the years as to which is the most appropriate way to rehabilitate the patient following ACL reconstruction and providing a defin- itive answer is difficult.

Certain factors need to be taken into account when developing a rehabilitation programme and can only be discerned by discussion with the surgeon.

These factors include: ● the initial graft strength ● fixation ● healing ● maturation of the graft

Other factors to be considered are: ● the effects of particular exercises on the ACL graft (see section below) ● the role of certain muscles in limiting stress on the ACL graft ● proprioception

Open versus closed kinetic chain exercises Anterior displacement of the tibia places greatest strain on the ACL, therefore those activities generating the greatest anterior translatory force, will cause the greatest elongation of the ACL.

It has long been believed that open kinet- ic chain (OKC) knee extension generates a potentially damaging anterior translatory shear at the knee. The degree of shear produced by the unopposed contraction of the quadriceps muscles depends on the angle of knee flexion. No anterior transla- tion force occurs at angles greater than 60-75º of flexion, with increasing levels occurring from 60º to full extension.

Therefore, OKC knee extension exercises should be avoided (especially between 45º flexion to full extension) because of the potential strain they place on the ACL graft.

Anterior displacement of the tibia places greatest strain on the ACL, therefore those activities generating the greatest anterior translatory force, will cause the greatest elonga- tion of the ACL. No anterior transla- tion force occurs at angles greater than 60-75º of flexion, with increas- ing levels occurring from 60º to full extension.

Closed kinetic chain (CKC) exercises such as squatting are believed to minimise the stresses placed on the ACL by decreasing shear forces through increased joint com- pression and muscular co-contraction. Squatting has been shown to produce less anterior shear than OKC exercises and pro- duce a co-contraction of the hamstrings (which pull the tibia backwards, resisting anterior tibial translation). CKC exercises would appear to be the most appropriate exercise form when rehabilitating ACL reconstructed patients.

Translation and rotation control training There has been considerable research to show that the ACL alone cannot withstand the forces applied on the knee during sporting activities and it requires the dynamic support of muscle co-activation in order to prevent stress. The hamstrings have been shown to be capable of restricting anterior tibial translation when contracting, there is also a protective reflex with the ACL mechanoreceptors sig- nalling excessive strain and causing a reflex contraction of the hamstrings. This reflex arc will be absent in the ACL defi- cient or reconstructed knee and co-activa- tion of the hamstrings need to be retrained during functional (CKC) activi- ties.

Figure 5 shows a patient using an EMG biofeedback unit to provide feedback on hamstring activation during a squat, though this could be achieved by palpa- tion. The aim is to achieve tension in the hamstrings not rigidity (a contraction not greater than 25% of maximum isometric voluntary contraction (MIVC)), this co- activation of the hamstring muscle is then incorporated into functional activities.

Earlier in this article the mechanism of injury for an ACL rupture was described, this involved considerable rotation of the lower limb away from that which is con- sidered normal alignment (Fig. 1). The hip was adducted and internally rotated, the

Figure 5: The use of EMG biofeedback to achieve hamstrings co-activation during a squat

main muscle responsible for drawing the limb back into a neutral hip position and so the femur back into normal alignment is the gluteus medius. In a similar manner to generating hamstrings co-activation, gluteus medius co-activation is encouraged to correct hip rotation and adduction during CKC exercises. These should be progressed by functional activ- ities as above.

Excessive pronation has been shown to be correlated with ACL injury (excessive pronators have 5º greater knee internal rotation at 5º knee flexion than is the norm). During CKC exercises and then functional activities the patient is encour- aged to maintain a sub-talar joint neutral position (at the ankle) to reduce the tib- ial rotation load placed on the knee, if necessary an orthotic device may have to be provided.

Proprioceptive training Damage to the ACL severely limits the pro- prioceptive data available from the knee and in order to prevent future damage, deficits in proprioception and joint posi- tion sense need addressing. Table 1 out- lines a progressive proprioception exercise programme, which can be adopted to retrain proprioception and joint position sense. Studies have compared outcomes when proprioceptive training has been used as an alternative to a standard strengthening programme, those patients rehabilitated using proprioception exer- cises have a much better outcome in terms of functional ability.

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