Genu recurvatum is a posture where the knees appear to bend backwards in standing. The recurvatum appearance is due to the knees being placed in a hyperextended position. The posture is easily identified when looking at a person from the side by the curved alignment of the legs. From the front, recurvatum standing posture can make the kneecaps appear to point inwards.
A while back I received this question in regards to another post on posture:
In healthy individuals without a history of knee injuries there are three main causes of genu recurvatum:
- Joint laxity (very flexible knees)
- Weakness of muscles around the knee
- Postural habits
The body will use knee hyperextension as a strategy for standing when it finds the position more stable or efficient than standing with the knees in neutral. Having “loose” joints makes it easier for the knee to go into a hyperextended position, but to explain why someone is standing this way we need to look beyond the knees. Knee alignment is influenced by both the alignment of the pelvis and hips above, and the ankle and foot below.
People who stand with their knees locked out often have an anteriorly tilted pelvis and increased lumbar lordosis. Anterior tilting of the pelvis causes relative flexion of the hip. The flexed position of the hip is countered by extension at the knee, leading to a hyperextended posture. These postural changes can be caused by weak glute and core muscles and tight hip flexors.
Below the knee there may be a lack of ankle flexibility causing the ankles to remain slightly plantar flexed. Collapsing of the arch at the foot level and related weakness of the arch supporting muscles can also be a factor.
Effects of Knee Hyperextension
In a healthy population, genu recurvatum is not often seen as problematic. There are several consequences to keeping this posture however that deserve consideration:
- Increased compression stress in the front inside corner of the knee
- Increased tensile stress on the back outside (posterolateral) corner of the knee
- Increased stress on the ACL
Increased genu recurvatum has been found to be a predictor of ACL injury. The reason may be because knee hyperextension makes the hamstrings (the muscles in the back of the thigh) less efficient by placing them in an elongated position, or from increased anterior (forward) translation force on the lower leg.
People who stand with their knees hyperextended can have poor proprioception control in the terminal degrees of knee extension. These individuals may perceive the hyperextended position as “normal”. The first step in correct this posture is increasing awareness of the difference between neutral knee alignment and the hyperextended position.
Gaining awareness of knee alignment can be done by using a mirror to provide feedback. The knees are brought to a neutral position by shifting the pelvis and hips forward so that a straight line would pass through the hip, knee, and ankle. Body weight should be balanced between the front of the foot and the heel. Once proficiency is achieved at sensing the difference between extension and hyperextension, work on maintaining neutral knee posture without a mirror. Single leg balancing activities can also be used to increase joint position awareness.
It’s commonly suggested for correcting knee hyperextension to focus on quadriceps and gastrocnemius strengthening, as these muscles directly control extension of the knee. But really there are no unimportant muscles in the body. Strengthening muscles in isolation doesn’t acknowledge or address the complexity of biomechanics.
A better approach is building overall strength and motor control, with emphasis on muscle balance and targeting muscle groups that are commonly underused in our modern lifestyles. (e.g. glutes, calves).
For example, people with lax knee joints often go into hyperextension when bending forward (e.g. brushing their teeth). The Romanian dead lift (video) can be used to improve eccentric control of the hips while keeping the knee in neutral alignment. Exercises that are used to correct anterior pelvic tilt would also help encourage good overall alignment.
Be mindful when working on these exercises to avoid locking out the knee or throwing the knee back into extension.
To improve gait mechanics for someone with knee hyperextension, practice maintaining a slight bend in the knee while walking. This trains the muscles around the knee to work together in creating stability. At first walking with a slightly bent knee will feel taxing, but over time the muscles of the leg adapt to working from a new position. Pay attention to not letting the trunk lean forward, or allowing the knees to move inward.
On stairs, focus on using a slow and deliberate motions. Avoid using momentum, especially during step-ups.
Hyperextended knee posture is often reduced when wearing heels, but this is a double-edged sword. Wearing heels too frequently encourages knee hyperextension when barefoot or wearing flat shoes.
Sports Specific Training
People with hypermobility should refrain from forcing their joints past their end range to reduce the risk of injury. The feedback systems within hypermobile joints can be less effective, so caution should be used when working at end range during activities that require a high degree of flexibility, such as yoga.
Athletes will want to work on preventing hyperextension and controlling knee position during sport specific activities, such as:
- Planting and cutting maneuvers
- Jump landings
- Sudden stops
It should be made clear that this article applies to hyperextended alignment of the knees in standing, and not a knee hyperextension injury, where the knee has been forcefully bent backwards.
It is also important to recognize that certain conditions can cause genu recurvatum. These include:
- A defined disorder of the connective tissue or bone including:
- Marfan syndrome
- Ehlers-Danlos syndrome
- Benign hypermobile joint syndrome
- Osteogenesis imperfecta disease
- Instability of the knee joint due to ligaments and joint capsule injuries
- Irregular alignment of the femur and tibia (e.g. congenital, growth plate injury)
- Certain diseases: cerebral palsy, multiple sclerosis, muscular dystrophy
- Muscle weakness from CVA (stroke), post-polio syndrome
Altering knee alignment can be complicated by the presence of any of these conditions, and may not be recommended if the hyperextended posture is being used to assist a person with profound strength deficits stand and walk.
- Loudon JK, Goist HL, Loudon KL. Genu recurvatum syndrome. J Orthop Sports Phys Ther. 1998 May;27(5):361-7.
- Loudon JK, Jenkins W, Loudon KL. The relationship between static posture and ACL injury in female athletes. J Orthop Sports Phys Ther. 1996 Aug;24(2):91-7.
- Ramesh R, Von Arx O, Azzopardi T, Schranz PJ. The risk of anterior cruciate ligament rupture with generalised joint laxity. J Bone Joint Surg Br. 2005 Jun;87(6):800-3.