Chondromalacia Patella; Runner’s knee

Common biomechanical faults

Increased Q –angle:

Normal – 14⁰ for men; 17⁰ for women. An increase in Q-angle results in increased lateral pull of the patella. This causes misalignment of the patella into femoral trochlear groove causing the imbalanced distribution of patella femoral compression force.

Overpronation:

The pronated foot can cause internal rotation of tibia which in turn results in the femoral internal rotation.  This excessive rotation creates mal-alignment at the knee joint and therefore causes altered patella femoral arrangement. Also, due to this excessive rotation, the patella may shift laterally.

Stretching of evertors (soleus, peroneals) and strengthening of invertors (tibialis posterior, flexor hallucis longus and flexor digitorum longus) can reduce overpronation.

FADDIR Hip joint:

–Flexed, adducted and internally rotated hip at foot strike.

–Tight hip flexors, Tensor Fascia Latae and adductors.

–Weak abductors and external hip rotators.

–This hip posture increases Q-angle and patella femoral malalignment and hence causing the problem.

Pelvic Trendelenburg:

Lateral pelvic tilt caused by weak hip abductors. This again causes femur to roll in and increase Q-angle.

Patella Alta: High sitting of the patella. It is common when patellar tendon is greater than the height of patella by 20%.

Muscular imbalance:

Tight muscles:

Rectus femoris tightness- affects patellar movement during flexion of the knee.

Iliotibial band: Tight ITB causes lateral pull of the patella.

Hamstring: increased knee flexion- increased dorsiflexion – compensatory over pronation in the talocrural joint.

Weak muscles:

Hip abductors and extensors

Vastus medialis- Functions to realign patella during knee extension. Thus, its weakness causes lateral drift of patella.

 

Where pain comes from?

The cartilage has no nerve supply. So where does the pain come from? Actually, there are a number of other sources of pain which are affected due to damaged cartilage. So, the patient may be pain-free although he can feel fine grating crepitus behind the kneecap unless other sources or structures are affected which have pain sensitized nerve endings.

• Lateral patella retinaculum: Most of this structure is formed by the illiotibial band (ITB) and is a highly innervated and pain sensitive. This is situated on the outside of the kneecap which is exactly where the patients show their pain is.Tightness of TFL which in turn tightens ITB, lateral hamstrings and lateral quadriceps muscles may easily sensitize lateral patella retinaculum.
• Bone bruising: Due to excessive corrosion of articular damage, the subchondrol bone may become traumatized, swollen or damaged. MRI scans often show oedematous bone adjacent to the site of cartilage softening.
• Due to excessive and repetitive compression at a particular point, the bony structure below the highly compressed or damaged cartilage may have eroded or damaged. The bone is a highly sensitive structure.
• Knee joint effusion: Degenerated articular cartilage can lead to swollen knee joint. This effusion may cause the distension of knee capsule and hence produce a vague sensation of pain around the knee cap.
• With poor assessment, sometimes fat pad irritation or patella tendon irritation is misdiagnosed as patellofemoral pain and/or chondromalacia patella.