Moving may be difficult because of disorders that restrict joint motion or that cause weakness, stiffness Joint Stiffness Joint stiffness is the feeling that the motion of a joint is limited or difficult. The feeling is not caused by weakness or reluctance to move the joint due to pain. Some people with stiffness... read more , tremor Tremor A tremor is an involuntary, rhythmic, shaking movement of part of the body, such as the hands, head, vocal cords, trunk, or legs. Tremors occur when muscles repeatedly contract and relax. (See... read more , or difficulty initiating movement (for example, Parkinson disease Parkinson Disease (PD) Parkinson disease is a slowly progressive degenerative disorder of specific areas of the brain. It is characterized by tremor when muscles are at rest (resting tremor), increased muscle tone... read more ). Movement may also be limited when motion causes pain Musculoskeletal Pain Pain is the most common symptom of most musculoskeletal disorders. Pain ranges from mild to severe and from acute and short-lived to chronic and of long duration and may be local or widespread... read more . People with pain in the muscles, ligaments, bones, or joints (see Introduction to the Biology of the Musculoskeletal System Introduction to the Biology of the Musculoskeletal System The musculoskeletal system provides form, stability, and movement to the human body. It consists of the body's bones (which make up the skeleton), muscles, tendons, ligaments, joints, cartilage... read more ) tend to consciously and unconsciously limit motion. This limitation of motion often gives the impression of weakness even though the nervous system and muscles are able to generate movement.
A joint may have limited range of motion because of
Previous joint injury causing significant scar tissue
Prolonged joint immobilization (for example, when a person's arm is paralyzed by a stroke or placed in a sling) causing shortening of the tendons
Fluid accumulation in a joint resulting from arthritis or an acute injury (giving a sensation that the joint is locked)
A piece of torn cartilage (resulting from an injury, typically in the knee) that blocks joint movement
Although many people complain of weakness when they feel tired or run down, true weakness Weakness Weakness refers to loss of muscle strength. That is, people cannot move a muscle normally despite trying as hard as they can. However, the term is often misused. Many people with normal muscle... read more means that full effort does not generate normal, strong muscle contractions. Normal voluntary muscle contraction requires the brain to generate a signal that then travels through the spinal cord and nerves to reach a normally functioning muscle. Therefore, true weakness can result from injury or disease affecting the nervous system, muscles, or connections between them (neuromuscular junction).
Doctors can often diagnose weakness based on the person's symptoms and the results of a physical examination. Doctors first try to determine whether the person can contract the muscles with normal strength. If muscle strength is normal, and the person has difficulty moving a joint, the doctor tries to move the joint for the person while the person relaxes (called passive motion). If motion is painful, joint inflammation may be the problem. If passive motion causes little pain but is blocked, joint contracture (for example, due to scar tissue) or stiffness due to spasticity or rigidity caused by a nervous system disorder may be the problem. If passive motion causes little pain and is not blocked, doctors encourage the person to try as hard as possible to move. If movement is still difficult and still does not cause pain, true weakness is possible.
For joints with a limited range of motion, joint flexibility can be maximized by stretching exercises and physical therapy Physical Therapy (PT) Physical therapy, a component of rehabilitation, involves exercising and manipulating the body with an emphasis on the back, upper arms, and legs. It can improve joint and muscle function, helping... read more .
If the joint's range of motion is severely restricted by scar tissue, surgery may be necessary.
The best way to relieve weakness is to treat the disorder causing it, but physical therapy often helps a lot even when no ideal drug treatment exists.