This increases the stiffness, tensile and compression strength. Potential benefits include increased grip strength, reduced morning stiffness and number of swollen joints. Symptoms may include swelling behind the knee, stiffness, and pain. It offers improved surface roughness, higher stiffness and reduced thermal conductivity. The typical features are of continuous joint pains, stiffness and swelling. Neck stiffness or neck pain are also relatively common. Other symptoms include swelling, joint stiffness and aching around the joint(s). Common symptoms include muscle weakness, cramps, stiffness, and tetany. Uncontrolled movement such as restlessness, tremors, and muscle stiffness may occur. Physical therapy is helpful to patients with joint stiffness and low muscle tone. Potential side effects include extrapyramidal symptoms, including tremor, muscle stiffness, and restlessness or akathisia. The shear modulus is one of several quantities for measuring the stiffness of materials. Headache, neck stiffness, and photophobia may occur. It results in pain, stiffness, and deformities. Stability requires the "stiffness" and "damping" terms to be positive.