Lateral thrust

Written by Dr Sheila Strover on March 14, 2025

Lateral thrust is a sudden sideways movement of the knee which occurs in the early stance phase of walking. It is also known as a 'varus thrust'. Page updated May 2024 by Dr Sheila Strover (Clinical Editor)

Lateral thrust is dynamic - at rest the knees look straight but, as the patient takes weight on the affected side, the knee thrusts outwards.

Such 'thrust' occurs when weight is taken on the leg but - because some structure on the lateral side is damaged and cannot support the load - the distribution of the force is not even on the two sides.

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Observing a patient's gait during consultation is important.

"...varus thrust visualized during gait is associated with knee [osteoarthritis] progression and should be a target of intervention development....Gait observation, perhaps coupled with a simple inspection of alignment in the standing patient, should be incorporated into the physical exam"

Leena Sharma et al

This failure to evenly distribute the load between the medial and lateral sides, leads to increasing load on the medial side, and may trigger the development of osteoarthritis.

Lateral thrust is a dynamic situation but may be a precursor to permanent bowing of the leg, or varus deformity.

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Lateral thrust due to posterolateral corner insufficiency

The structures of the posterolateral corner - towards the back of the knee on the lateral side - provide the primary restraint to both varus forces and also to posterolateral rotation of the tibia.

"....a PLC injury can be overlooked or misdiagnosed. Left untreated, it can cause chronic pain and residual instability....When the static stabilizers of the knee are injured, the dynamic stabilizers....[lateral collateral ligament], [popliteofibular ligament], arcuate ligament complex, fabellofibular ligament and posterolateral capsule.... cannot function properly....This causes a varus thrust gait in the stance phase, resulting in abnormal gait..."

Oog-Jin Shon et al

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Lateral thrust due to medial compartment insufficiency

Another cause of subtle lateral thrust is early deterioration of the normal 'joint spacers' on the medial side - that is, the medial meniscus and/or the medial joint cartilage, or after a meniscectomy when the meniscus has been surgically removed.

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Does high tibial osteotomy correct lateral thrust?

High tibial osteotomy is a surgical procedure to correct lateral thrust, hopefully before arthritis intervenes.

"Good clinical outcomes after high tibial osteotomy can be expected with a lateral thrust of ≤3.0°, indicating that the target hip–knee–ankle angle should be 2.0° valgus. In cases where valgus alignment is insufficient, lateral thrust may develop, which should be assessed using gait analysis."

Toshiki Azuma et al

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Forum discussions

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