At rest the knees look straight but, as the walker person takes weight on the affected side, the knee thrusts outwards.
At rest the knees look straight but, as the walker person takes weight on the affected side, the knee thrusts outwards.
Why does lateral thrust gait occur?
Lateral thrust occurs when weight is taken on the leg but the distribution of the force is not even on the two sides because some structure on the lateral side is damaged and cannot support the load.
This may include damage to the lateral meniscus, or to one or more of the ligaments on the lateral side. 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.
Peer-reviewed paperQuote from peer-reviewed paper:
"...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"
Citation: Sharma L, Chang AH, Jackson RD, Nevitt M, Moisio KC, Hochberg M, Eaton C, Kwoh CK, Almagor O, Cauley J, Chmiel JS. Varus Thrust and Incident and Progressive Knee Osteoarthritis. Arthritis Rheumatol. 2017 Nov;69(11):2136-2143. doi: 10.1002/art.40224. PMID: 28772066; PMCID: PMC5659924.
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.
Peer-reviewed paper
Quote from peer-reviewed paper:
"....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..."
Citation: Shon OJ, Park JW, Kim BJ. Current Concepts of Posterolateral Corner Injuries of the Knee. Knee Surg Relat Res. 2017 Dec 1;29(4):256-268. doi: 10.5792/ksrr.16.029. PMID: 29172386; PMCID: PMC5718794.
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.
Does high tibial osteotomy correct lateral thrust?
High tibial osteotomy is a surgical procedure to correct lateral thrust, hopefully before arthritis intervenes.
Peer-reviewed paperQuote from peer-reviewed paper:
"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."
Citation: Azuma T, Sasaki K, Yokota A, Watanabe Y, Kuroda K, Takahashi M, Asa R, Sakamoto K, Ohta Y, Haba T, Goto S. Association between clinical symptoms and lateral thrust 12 months after high tibial osteotomy. J Phys Ther Sci. 2023 Jun;35(6):465-470. doi: 10.1589/jpts.35.465. Epub 2023 Jun 1. PMID: 37266363; PMCID: PMC10231975.
Forum discussions
- "Re: in search of PLC info"
A patient discusses the knee thrusting laterally after a dislocated knee replacement.