Patellofemoral Disorders (Anterior Knee Pain)

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Patellofemoral Disorder Characteristics

Pain in the front of the knee joint

• On walking down stairs or hills
• On squatting
• On kneeling
• Sitting in cramped conditions (economy class aircraft seats; cinema etc)
• Sometimes in bed when in side-lying

What is happening to cause the pain?

The patella (kneecap) is contained in a strong tendon attaching the four muscles which straighten the knee, to the tibia (shin bone). These muscles are located on the front of the thigh.

As the knee bends and straightens, the patella glides up and down, running in a groove between the condyles (knuckles) of the femur.

A small muscle, Vastus Medialis Oblique (VMO) keeps the patella tracking within its groove, by exerting a pull on its inner side.

Attached to the outer side of the patella, is a fibrous structure (the lateral retinaculum) which, in turn, is attached to a strong band of fibrous tissue, the ITB (iliotibial band) running up the outside of the thigh. If the ITB is very tight, it exerts a strong lateral pull on the patella, overwhelming VMO as it attempts to align the patella within its groove.

If the patella is pulled laterally out of its groove, its undersurface grinds against the outer condyle of the femur as the knee bends and straightens.

Over time, this grinding action wears away the protective articular cartilage on the back of the patella and on the condyle of the femur.  This leads to a form of arthritis, as patches of bone become exposed. This does not mean, however, that the knee joint itself is osteo-arthritic. The arthritic changes are confined to the surfaces between the patella and the condyle of the femur, and are external to the weight-bearing surfaces of the knee joint.

Wearing away of the articular cartilage leads to pain, particularly noticeable when the knee is bent.

	The iliotibial band

Predisposing factors

• Flat or overpronated feet
• Weak hip lateral rotators
• Weak VMO (vastus medialis oblique)
• Tight iliotibial tract
• Tight lateral retinaculum

 

Physiotherapy treatment

• Mobilisations of the patella
• Stretching of the ITB (iliotibial band)
• Stretching of the quadriceps muscles, with particular emphasis on vastus lateralis
• Strengthening of VMO
• Strengthening of the hip lateral rotators
• Ultrasound or other modalities to reduce swelling
• Taping of the patella during activities, to prevent lateral glide if pain persists
• Video gait analysis or use of force plate to assess over-pronation of the feet and gait pattern
• Prescription of corrective orthotics if necessary, or recommendation for more suitable motion control footwear