The effect of alignment on patellofemoral contact pressures has already been mentioned. When considering the biomechanics of the patellofemoral Joint, one should not just consider knee biomechanics, but the biomechanical effect of the entire lower limb. In fact there is a case to be made that trunk movements and trunk muscle action could have an effect on patellofemoral joint function. The abnormally large range of external hip rotation necessary in ballet dancing can be a cause of patellofemoral problems. In a survey (Reid 1988), 14-20% of
presenting problems were at the knee and 50% of these were pateliofemoral. There was also a marked lowering of range of internal hip rotation.
Femoral anteversion is a frequently observed finding in pateliofemoral pain. External tibial torsion is similarly implicated. These may or may not occur together, and when they do they cause the orientation of the patella to appear to squint. The effect that this has on the pateliofemoral contact pressures has already be mentioned, but there has been work which has shown the correlation between torsion and pateliofemoral problems.
Torsion in long bones takes place between the epiphysis and the diaphysis. This means that in the femur it causes change in angle between the shaft and the head (Grays Anatomy 36th Edition p392, Eckhoff et al. 1994), so that the neck is carried forward on the head. This causes the transverse axis of the lower end of the femur to make an angle with the transverse axis of the head. When there is increased femoral anteversion the shaft is twisted medially. On the other hand there may be posterior femoral version, although this is not nearly as common. Fabry et al. (1994) found that in a group of children, anterior femoral torsion was associated with internal tibial torsion in 59.7% of them, and 40.3% with external tibial torsion.
Le Damany (translation of the original work 1994) has traced the normal development of tibial torsion. Fabry et al. (1994) discussed normal and abnormal torsional development in children. We are born with marked femoral
anteversion which slowly derotates throughout childhood. In a correction group with intoeing, in 20.5 % of the children the anterior torsion of the femur
decreased, but 62.9% developed compensatory external tibial torsion. The neonate has a perfectly neutrally aligned tibia which gradually externally rotates throughout childhood. This shows that slight external tibial torsion is normal. All the factors which cause the femur not to derotate enough, or the tibia to rotate too much, are not known.
External tibial torsion may or may not be associated with proximal tibia vara, sometimes called the bayonet sign, because the tibial alignment resembles a bayonet. This accentuates the laterality of pull of the patellar tendon. 1.5.4. Iliotibial Band or Tract
Although there have not, to the knowledge of the author, been quantitative studies made, the presence of a tight iliotibial band (ITB) has frequently been observed clinically with pateliofemoral pain and dysfunction. It must have some effect on the symptoms experienced but what the biomechanical effects are has not been elucidated.
It has been demonstrated in an in vivo experiment that the ITB is tensioned at the part of the gait cycle when gluteus medius, vastus lateralis, and tensor fascia lata are active, that is early and mid stance (Huggler and Jacob 1983). Pare et al (1981) showed in cadavers that action of tensor fasciae latae could be
transmitted to the knee via the ITB. They investigated the action of these muscles by EMG, in certain exercises and everyday activities. They found that
the posterolateral fibres were active in internal hip rotation. In walking these fibres were active near “heel strike”, and the anteromedial fibres were active in jogging, running, and sprinting near “toe off’. However, gluteus maximus is
also inserted into the ITB, and is a large and powerful muscle. Although its main action is to balance the trunk, it can also externally rotate the hip as well as extend the hip. In the propulsive part of the stance phase of walking,
plantarflexion occurs without much electrical activity occurring in the
gastrocnemii (Sunderland et al 1980). Forward propulsion is brought about by the forward fall of the trunk (Gage 1990). Gluteus maximus is silent during this phase of normal walking (Pare et al. 1981), but when the speed o f progression is increased it becomes active.
Although Huggler and Jacob (1983) demonstrated an increase in the tension when these muscles were active, and the presence of tightness in the structure clinically in some individuals suggests a cause which might be muscular, there is a body of opinion which considers that the tension has a purely passive cause (Kaplan 1977, and Hassler and Jakob 1981). These authors consider that changes in knee angle alone cause changes in tension of the 1TB.
1.5. 5. Lower Leg and Foot Alignment
Carson et al. (1984) wrote two papers on evaluation of pateliofemoral disorders. Part 1 consisted of a scheme of physical examination in patients, and in Part 11 there was a resume of radiographic examination. The physical examination included, not only a physical examination o f the knee, but also a series of tests
and m easurem ents o f the whole lower limb. There are many clinicians who would use this approach.
These authors believe that the comm on denom inator o f malalignment appears to be abnormal pronation o f the subtalar joint, which causes a com pensatory internal rotation o f the tibia, and that the increased rotatatory stress is absorbed through the peripatellar soft tissues o f the knee. They summarised this abnormal subtalar pronation in the following way;-
+ J/ C G e n u \ a r n . T r i c e p s s u r a c H i n d f o o t F o r e l o o t T i b i a v a r a c o n t r a c t u r e v a r u s s u p i n a t i o n
\
C o m p c n s a t o r v s u b t a l a r j o i n t p r o n a t i o nI
I /
\
. . O b l i g a t o r v i n t e r n a l t i bi a! P n m a n su blal.if j o . n . r o . a u o n ( m a y be p r o n a t i o n i n c r e a s e d or p r o l o n g e d )I
. A b n o r m a l r o t a t i o n a l s t r e s s a b s o r b e d b y s o ft t is s u e s at k n e e j o i n tI
P e r i p a t e l l a r a n d a n t e r i o r k n e e p a i n• Genu vara=genu varum
Fig 1.7. Causes o f primary and secondary excessive sub-talar pronation (from Carson et al. 1984)
O ne cause o f subtalar pronation is the presence o f tight plantarflexors. This may be due to tightness o f the gastrocnem ii alone or o f the deep plantarflexors as well (R oot, 1977). These tw o factors may be dilTerentiated by the persistence o f
limited plantarflexion when the knee is bent, if the deep flexors are tight. The minimum dorsiflexion which is necessary in midstance is 10° beyond the right angle (Root 1977). If there is not sufficient movement possible, either there is premature heel raise, or a compensatory pronation.
Inman et al. in their classic book Human Walking (1981, 2nd ed. 1993), explain the concomitant sub-talar pronation, plantarflexion, and internal tibial rotation, in early stance phase of walking. They assert that the maximal sub-talar pronation in normal function is 4°, and in mid and late stance phase there is gradual external rotation of the tibia.