Knee joint - hyperextension with altered patterns of rotation

Generalized joint hypermobility (GJH) affects the knee joint is two ways: 

 

  • Hyperextension of the knee which affects standing posture and LE weight-bearing function.
  • Increased range of knee rotation. 

Knee hyperextension

Hypermobility of the knee commonly recognised. 

knee hyperextension supine.jpg

The knee can be extended beyond 00  sometimes as much as 10-150

 

knee hyperextension_1.jpg

The child stands with the knee in hyperextension and in this position the line of gravity falls posterior to the knee flexion/extension axis. 
No muscle action is needed to maintain weight-bearing knee extension. 
 
The quadriceps muscles are often weak in inner range. 

Hyperextension of the knee is usually associated with anterior pelvic tilt and extension of the lumbar spine. 

 


Knee rotation

A typically developing child has 8-100 of medial and lateral rotation. 

Sitting lat tibial rotation.jpgThe resting position for the foot is 00.

The child sits and stands with the feet parallel or in a few degrees of lateral rotation. 


Knee rotation is best tested in prone with the knee flexed to 900

L 2y assess K rot lat.jpgx    L 2y assess K rot med.jpg


In GJH lateral rotation is often increased, with very limited range of medial rotation. 

Sitting lat tibial rot_1.jpg

The resting position of the knee is 10-150 of lateral rotation. This is referred to as lateral tibial torsion. 

The child stands and sits with the feet turned out at the knee. 


Medial rotation of the knee is often restricted to 00

Standing feet wide apart.jpgThe combination of restricted adduction/medial rotation of the hip in extension along with lateral tibial torsion results in the child standing with the feet wide apart and turned out. 

This position is comfortable for the child. 

 


A quick test for the impact of hip and knee restricted movement on standing posture. 

Ask a child who habitually stands with the legs wide apart and the feet turned out to stand with the feet parallel and about 10 cm apart for 20s.

Enquire whether this position is comfortable - or if it gets "boring". Ask the child to identify where he/she feels the discomfort. 

Now let the child stand with the feet about 20 cm apart and and then in the habitual wide stance. Enquire each time about comfort.

Children are usually quite clear about the difference in comfort between the different positions. 


Tibial torsion and walking 

Lateral tibial torsion affects walking

During the stance phase the foot is rotated laterally with respect to the line of progression. 

T stepping 4.jpg

In a child with good LE alignment the foot is positioned with a few degrees of lateral rotation with respect to the line of progression when walking. 
This allows the lower leg to pivot forwards over the foot during mid to late stance, and then allows for effective push-off. 

right foot midstance.jpg   right foot pivot.jpgRight foot push off.jpg

If the foot is positioned with lateral rotation relative to the line of progression, the tendency is for the child to roll sideways over the foot.  

T stepping 2 1.jpg   T stepping 2 2.jpg


Why do children develop lateral tibial torsion?

The altered pattern of ROM of the knee is probably associated with the tightness in the fascia lata and associated deep fascia. 

fascia lata.jpg 

Sitting with the hips in medial rotation (W-sitting or side sitting) also imposes a lateral torsion force on the knee joint. 

J w-sitting.jpg    J w-sitting 1.jpg


Cross leg sitting is uncomfortable

The restricted range of medial rotation of the knee makes sitting cross legged on the floor uncomfortable

benni sitting cross legged.jpg

 

In cross leg sitting the knee is typically medially rotated. If medial rotation is limited to 00, cross leg sitting imposes a strong medial rotation stretch on the knee.

If you ask a child who does not like sitting cross legged where they experience discomfort they wil usually indicate the lateral aspect of the lower leg. 

Clinical application

Clinically I have found that active stretching of the tight fascia lata a related structures followed by standing activities with the feet parallel does improve the range of medial rotation of the knee and improve foot placement in walking and running. 

More about this in the active mobilization tutorial. Retraining foot position in walking and other weight bearing activities is covered in the strengthening the lower limb tutorial.