Normal Joint Flexibility and Laxity
According to Internal Medicine News, the normal range of joint laxity varies between different people and over time. It's a fact that some people are born more flexible than others, while others may have consciously worked at expanding their range of motion by participating in activities such as yoga or stretching exercises. We know that joint mobility is greater in women than men, and children are also quite flexible, though flexibility decreases with age.
Conditions That Cause Joint Laxity
Several syndromes with abnormal joint laxity are suggestive of a genetic cause. Those conditions include Marfan syndrome, Stickler syndrome, and Ehlers-Danlos syndrome. Other conditions — heritable disorders of connective tissue — may also fit into this group. Many patients with heritable disorders of connective tissue have dental crowding or a high, narrow palate. Other characteristics, depending on the syndrome, include: soft skin, easy bruising, hernias, early-onset osteoarthritis, gastric or bowel problems, postural orthostatic tachycardia, and neurally mediated hypotension.
Marfan patients face aortic root dilation and rupture. Stickler syndrome patients are at risk for osteoarthritis and skeletal dysplasia. Most of the conditions that fall under Ehlers-Danlos syndrome deal with joint laxity and soft skin to some degree.
Laxity in Knee Osteoarthritis
Laxity in osteoarthritic knees has not been extensively studied in humans. In 1999, researchers did take on the task. They evaluated varus-valgus and anteroposterior laxity in 25 young study participants. There were also 24 older participants without clinical osteoarthritis, without radiographic osteoarthritis or prior knee injury — and 164 study participants with knee osteoarthritis and osteophytes.
Researchers concluded that increased laxity associated with osteoarthritis may actually predate the disease. Loss of cartilage is linked to greater varus-valgus laxity; it's possible that varus-valgus laxity increases the risk of knee osteoarthritis and also contributes to the progression of the knee osteoarthritis.
Another study, published in 2005, assessed the associations between changes in joint structure, such as joint space narrowing or osteophyte formation and laxity, and joint malalignement and laxity in people with knee osteoarthritis. After performing certain tests, researchers concluded that both joint space narrowing and malalignment are related to joint laxity.
Patients with knee laxity, depending on its severity, may be advised to avoid high impact activity or resistance training. In these cases, low-resistance training is used to help stabilize the joint. Bracing and supporting the knee may be beneficial as well.
Laxity in Ankle Osteoarthritis
Typically, chronic ankle laxity begins with an injury to the ligaments that keep a normal ankle stable. X-rays and MRI help confirm a diagnosis of laxity of the ankle. Physical therapy, bracing, ice, elevation, and nonsteroidal anti-inflammatory drugs are used to rehabilitate the ankle.
Laxity in Hip Osteoarthritis
One of the primary conditions associated with hip laxity is Developmental Dysplasia of the Hip (DDH), an abnormal formation of the hip joint whereby the ball and socket do not fit together well. In DDH, the ligaments of the hip joint may be loose, causing laxity or instability. In some children, at birth, the thighbone is loose in the socket. In others, the thighbone is completely out of the socket. The looseness can worsen as the child grows and becomes more active. The condition, if untreated, has been associated with an increased risk of developing osteoarthritis.
Genetic Causes of Joint Laxity. Internal Medicine News. Howard P. Levy. 04/01/08.
Laxity in healthy and osteoarthritic knees. Sharma L. et al. Arthritis & Rheumatism. 1999May;42(5):861-70.
Structural joint changes, malalignment, and laxity in osteoarthritis of the knee. van der Esch M. et al. Scandinavian Journal of Rheumatology. 2005 Jul-Aug;34(4):298-301.
Ankle Laxity. Cedars-Sinai. Accessed 1/29/13.
Developmental Dislocation (Dysplasia) of the Hip (DDH). OrthoInfo. Accessed 01/29/13.