Why your knees give way when walking: reasons, how to treat and what to do

Stability of the musculoskeletal system is a prerequisite for its proper functioning. Correct biomechanics of movements are ensured by:

• articular capsule (capsule);
• menisci;
• lateral and cruciate ligaments;
• tendon apparatus.

If any of these structures are damaged, the relative position of the articular surfaces is disrupted and instability develops.

Causes of weakness in the legs

Neurological diseases

Pathology of the nervous system is a common cause of weakness in the legs. Impaired impulse transmission through central or peripheral motor neurons leads to an objective decrease in muscle strength - flaccid or spastic paresis. Only the lower extremities are affected or the process spreads to the arms. In practical neurology the following conditions are encountered:

• Strokes.
  Local damage to the frontal cortex provokes central monoparesis. Loss of motor functions is accompanied by increased tendon reflexes in the lower extremities, pathological foot signs, and spastic hypertonicity.
• Amyotrophic lateral sclerosis.
  Degenerative motor neuron disease causes muscle weakness in the legs (one or both legs). There is awkwardness in the ankle joint, stiffness of the foot, gait changes, and patients stumble.
• Guillain-Barre syndrome.
  Acute autoimmune polyradiculoneuropathy begins with weakness of the buttocks and thighs with paresthesia of the toes. Flaccid paresis is accompanied by pain in the lumbosacral region and pelvic girdle, radiating to the leg, and signs of tension in the roots.

Paresis of the extremities occurs due to injuries and is the result of a violation of the integrity of the pathways (due to wounds, fractures, after operations). With unilateral damage to the spinal cord at the level of the lumbar segments, weakness occurs in one leg (lower monoparesis). When the peroneal nerve is damaged, patients notice a drop in the foot, and the gait takes on the appearance of a “rooster” or “chasing.”

Spinal diseases

Among the causes of weakness in the legs, an important place is given to damage to the structures of the spinal column. Compression of the nerve roots is caused by osteophytes in osteochondrosis, intervertebral hernias, destroyed vertebral bodies - due to osteoporosis, tuberculosis, and metastatic process. This situation is observed with spondyloarthrosis, spondylolisthesis (displacement of vertebral segments).

Pain and weakness in the legs are typical signs of radiculopathy, and their location corresponds to the affected nerves. The characteristic pain syndrome is the type of lumbodynia and lumbar ischialgia, which intensifies with movement and lifting heavy objects. The picture is complemented by sensory disturbances (numbness, paresthesia), muscle atrophy, and vegetative-trophic changes on the affected side.

Endocrine pathology

Hormonal disorders often provoke weakness in the legs; symptoms can be caused by disorders of many types of metabolism - protein, lipid, carbohydrate, energy, electrolyte. Damage to muscles, myoneural connections or nerve pathways is observed. The cause of weakness in the legs should be sought among the following conditions:

• Hypercorticism.
  It is characterized by a gradual decrease in strength and atrophy of the proximal muscles of the limbs, poor tolerance to physical activity. Additional signs are stretch marks on the skin, arterial hypertension, and weight gain.
• Addison's disease.
  It manifests itself as pathological fatigue, a long period of recovery after exercise, and cramps of the lower extremities. True muscle weakness with loss of strength is less common.
• Hyperaldosteronism.
  Neuromuscular disorders with increased secretion of aldosterone are accompanied by persistent weakness; with a protracted course of the disease, atrophy of the proximal areas occurs.
• Hypothyroidism.
  A deficiency of thyroid hormones causes weakness and pain in the legs (myalgia). The proximal muscles are involved, muscle spasms appear, and the processes of contraction and relaxation slow down.
• Thyrotoxicosis.
  Weakness and atrophy of the muscles of the proximal limbs are observed, although the patients themselves often do not feel discomfort. The disease can be complicated by myasthenia gravis and periodic paralysis.
• Hyperparathyroidism.
  Damage to the femoral and shoulder muscles is typical. Weakness and muscle atrophy are combined with increased tendon reflexes.

In long-term diabetes mellitus, symmetrical distal sensorimotor polyneuropathy is detected. Over time, sensory disorders (hypo- and paresthesias, pain) are accompanied by weakness of the small muscles of the foot, and the Achilles reflexes decrease or completely disappear. Involvement of the proprioceptive system is indicated by instability in the Romberg position.

Myopathies

Weakness in the legs due to muscle damage occurs not only with endocrine pathology. The etiological structure of myopathies is represented by immunopathological, infectious-inflammatory, metabolic disorders, and includes hereditary diseases. The following conditions cause myopathic weakness in the legs:

• Autoimmune.
  Dermatomyositis or polymyositis affects the proximal muscles, with weakness ranging from difficulty climbing stairs to complete immobility. Characterized by myalgia, weight loss, fever. Raynaud's phenomenon and polyarthritis are often observed.
• Infectious.
  Accompanied by local or diffuse pain and muscle swelling. Weakness due to parasitic infestations (toxoplasmosis, trichinosis) can mimic polymyositis. Pseudohypertrophy of the pelvic girdle muscles is typical for cysticercosis.
• Electrolyte.
  Hypokalemia is characterized by myalgia, a feeling of tired legs, weakness; the symptoms of hypomagnesemia are associated with impaired neuromuscular conduction. An increase in calcium concentration provokes weakness and stiffness of movement, which is manifested by a “duck” gait.
• Exchange.
  Disorders of muscle glycogen and lipid metabolism are characterized by low tolerance to physical activity and weakness of the pelvic and shoulder girdle muscles. After prolonged stress, myalgia, convulsions, and myoglobinuria appear.
• Mitochondrial.
  Fatigue and proximal muscle weakness in the legs occur due to progressive ophthalmoplegia. Decreased muscle strength occurs in MERFF, MMC, NARP syndromes.

Granulomatous myositis in sarcoidosis is accompanied by slowly increasing weakness of predominantly the proximal muscles of the extremities and knots in the muscles. Any ARVI is manifested by aches and fatigue, myositis with muscle swelling and pain is possible. With enterovirus infection, a dermatomyositis-like syndrome is sometimes observed.

Progressive muscular dystrophies

Many myodystrophies begin with weakness of the leg muscles - hereditary diseases caused by mutations in the genes responsible for the synthesis of certain structural proteins. With Duchenne dystrophy, the muscles of the hips and pelvic girdle are first affected - the gait becomes “duck-like”, it is difficult for children to climb stairs or stand up from a squatting position. Muscle tone decreases, pseudohypertrophy and flexion contractures occur.

The same symptoms, but with later development and slow progression, are characteristic of Becker muscular dystrophy. The juvenile form of Erb-Roth also debuts with damage to the pelvic girdle and weakness of the gluteal muscles. Deep reflexes of the lower extremities gradually disappear. With Davidenkov's myopathy, the muscles of the foot suffer: flexors, abductors. First, difficulties appear when running, then - a “rooster” gait, the inability to stand on your heels.

Myasthenia gravis

Severe weakness in the legs and fatigue are observed with myasthenia gravis. The disease is based on autoimmune aggression against acetylcholine receptors at the myoneural synapse. Symptoms increase with exertion, decrease after rest, and return again from repeated stress. The proximal legs and arms are most often involved, with tendon reflexes remaining unchanged.

The development of myasthenia gravis is associated with tumor and hyperplasia of the thymus, autoimmune diseases - thyroiditis, rheumatoid arthritis, lupus erythematosus. Predisposing factors include infectious pathology and surgical interventions. Taking certain medications plays an important role: aminoglycosides, calcium channel blockers, quinine.

Vascular disorders

Leg weakness as a symptom of vascular disorders accompanies varicose veins, obliterating endarteritis, and atherosclerosis of the lower extremities. Dilatation of the saphenous veins of the leg is accompanied by increased fatigue, a feeling of heaviness and fullness, and swelling, which intensifies in the evening. Pain along the affected veins and cramps in the calf muscles often occur.

Typical signs of occlusive arterial disease are rapid fatigue of the legs when walking, “intermittent claudication.” Tissue ischemia is manifested by pain, a feeling of numbness and compression in the muscles under load. After rest, the symptoms gradually disappear, but when walking resumes, they develop again. With obliterating endarteritis, weakness is observed in the left or right leg, while atherosclerosis is usually a bilateral process.

Intoxication

Sometimes the cause of weakness in the leg muscles is damage to the nerve and muscle tissue by toxic substances. Organophosphorus compounds and carbamates (insecticides), which inhibit cholinesterase activity, have a negative effect on the myoneural synapse. The function of nerve fibers and ganglia is disrupted by heavy metals: lead, thallium, mercury, arsenic, tellurium.

Alcoholic polyneuropathy, which primarily affects the lower extremities, deserves special attention: the legs first hurt, then weakness appears. Paresis is characterized by muscle hypotonia with a sharp decrease in proprioceptive sensitivity, loss of tendon and periosteal reflexes, and ataxia. Muscles quickly atrophy.

Symptoms accompanying weak knees

Any serious illness begins with mild discomfort, which gradually intensifies and acquires additional symptoms. Weakness and fatigue in the knees, forcing you to take breaks from walking and performing other physical activities, are accompanied by symptoms:

• clicking in the knee joint when lifting weights, running, jumping;
• trembling and “pins and needles” sensation;
• skin redness, swelling;
• heaviness and fatigue in the morning after waking up;
• dilatation of the veins of the lower leg;
• pain that spreads to the thigh and lower leg.

The diagnosis depends on which symptoms are more pronounced. Athletes and people involved in amateur sports experience such sensations after a long workout or after a knee injury. Symptoms intensify with changes in weather and climate, then subside. These are physiological processes that are rarely associated with serious diseases.

The risk group for the development of knee joint pathologies includes older people and those who engage in heavy physical labor with heavy lifting for a long time. Over time, the cartilage tissue becomes thinner, the joint loses calcium, heaviness and pain develop, and the legs give way at the knees.

Sometimes children complain of similar symptoms. This is due to previous infectious diseases, for example, staphylococcal sore throat. Doctors diagnose rheumatoid arthritis using a biochemical blood test, ultrasound, and examination.

Diagnostics

Clinical examination data, supported by the results of additional methods, help to understand what disease caused weakness in the legs. The list of diagnostic procedures is determined by a neurologist based on information obtained during a survey and neurological examination of the patient. The following tests may be performed:

• Blood tests.
  In the hemogram, attention is paid to red blood counts, leukocyte count, and ESR. Biochemical analysis can detect hormonal or electrolyte imbalances, muscle enzymes, and specific antibodies.
• Radiography.
  The condition of the bone structures of the spine and skull can be assessed using conventional photographs taken in two projections. But the study has low resolution and does not detect changes in soft tissues.
• Tomography.
  CT is the preferred method for visualizing recent strokes, tumors, hematomas, and posterior fossa fractures. Diffuse pathology of the substance of the spinal cord and brain is more accurately determined by magnetic resonance imaging.
• Myelography.
  The patency of the cervical canal is determined by introducing a radiopaque contrast agent into the subarachnoid space. Myelography is indicated for intervertebral hernias, spinal injuries, and tumors.
• Electroneuromyography.
  Diseases accompanied by nerve conduction disorders are diagnosed using ENMG data. During the study, the peripheral nerve is stimulated with electrical impulses and the muscle response is subsequently recorded.

To identify vascular diseases, ultrasound angioscanning and rheovasography are prescribed. Endocrinopathies require ultrasound examination of the thyroid and parathyroid glands, adrenal glands; in persons with myasthenia gravis, the size of the thymus is assessed. Diagnosis of hereditary diseases is carried out using cytogenetic and molecular genetic tests.

Foot massage

Diagnostics and prevention

To understand the causes of fatigue and weakness in the legs, you need to contact a number of specialists: orthopedist, surgeon, neurologist, endocrinologist, gynecologist, therapist, cardiologist, rheumatologist. To make a diagnosis, you need to undergo a number of tests:

• blood for ESR and glucose;
• blood for C-reactive protein;
• general urine analysis.

The patient is recommended to visit an ultrasound room, MRI and CT scan, and have an X-ray of the knee joints done. If necessary, a puncture of the joint fluid is prescribed.

When the cause of the disease is determined and treatment is prescribed, a course of painkillers and anti-inflammatory tablets or injections is recommended to relieve symptoms in the knee joint area. Local anesthetics and warming ointments and gels have a good effect.

Systematic weakness and pain in the limbs is a reason to undergo a serious examination. The earlier the causes of changes are identified, the easier and more effective the treatment is, the main task of which is not to relieve symptoms, but to prevent tissue destruction and the development of complications.

Prevention of diseases of the lower extremities and the entire musculoskeletal system comes down to an active lifestyle, proper nutrition, blood pressure control and timely treatment of infections. In this mode, a person can delay the appearance of problems with the musculoskeletal system for many years.

Treatment

Help before diagnosis

Acute conditions in which severe weakness in the legs appears are usually provoked by strokes and injuries. Urgent measures for violation of vital functions include intubation with mechanical ventilation, stabilization of blood pressure, elimination of cerebral edema. Undifferentiated therapy for strokes is carried out with cerebroprotective agents. Suspicion of spinal injury requires immobilization of the cervical spine and transportation on a rigid stretcher.

Conservative therapy

Treatment of muscle weakness in the legs is aimed at eliminating the cause and pathological mechanisms involved in its development. Therapy of acute conditions and supportive correction of chronic diseases are carried out using medications of various groups. When strength in the limbs decreases, the use of the following drugs is pathogenetically justified:

• Neuroprotectors.
  They are used to minimize the negative impact on neurons and protect them from damage. Antioxidants (Mexidol, lipoic acid), vasoactive agents (nimodipine, vinpocetine), nootropics (piracetam) have these properties.
• Immunocorrectors.
  Diseases of autoimmune origin are treated with cytostatics (methotrexate, azathioprine, cyclosporine), immunoglobulins, and glucocorticoids. Steroid drugs are indicated as anti-inflammatory, membrane-stabilizing agents, for replacement therapy of Addison's disease.
• Detoxification.
  The binding and removal of toxic substances from the body is ensured by complexing agents (unithiol, sodium thiosulfate, calcium thetacine) and infusion therapy. In severe cases, extracorporeal detoxification methods (hemosorption, plasmapheresis) are recommended.

Myasthenia gravis requires the prescription of anticholinesterase drugs; for vertebrogenic radiculo- and neuropathies with pain, NSAIDs and B vitamins are used. The rehabilitation program for patients with weakness in the legs includes physiotherapy, massage, and exercise therapy. Complex treatment of paresis involves kinesiotherapy and orthopedic correction.

Surgery

The need for surgical correction with removal of the thymus gland arises in myasthenia gravis. Brain hematomas are surgically eliminated; for ischemic strokes, reperfusion techniques are used (selective thrombolysis, endarterectomy, bypass surgery). To eliminate compression of the spinal roots, decompression operations are necessary.