The causes of muscle and joint pain can be mechanical, inflammatory, infectious, metabolic, medication-related or systemic. They may affect the muscles alone, the joints alone, or both, depending on the location, stiffness, presence of swelling, relationship to physical exertion and general symptoms.
Muscle pain
Intense or unusual physical exertion: Minor damage to muscle fibres can trigger an inflammatory response known as delayed-onset muscle soreness. In this case, the pain is often diffuse, tender to the touch and temporary (1).
Mechanical or myofascial overload: poor posture or local overuse subjects the muscle to repeated stress, which can lead to persistent tender points (2, 3).
Muscle trauma or injury: a strain, tear or contusion can damage the fibres or their blood supply, mechanically causing more localised pain – which can sometimes be sudden – along with functional impairment.
Stress and nervous tension: stress can increase muscle tone and contribute to muscle spasms and muscle pain.
A viral infection or a general inflammatory condition: during infections causing flu-like symptoms, inflammatory cytokines can cause diffuse myalgia (muscle pain) and a feeling of aching muscles.
Metabolic or endocrine disorders: hypothyroidism, iron deficiency, and sometimes vitamin D deficiency can contribute to chronic myalgia or muscle weakness. This pain is prolonged, not readily explained by physical exertion, and associated with other general symptoms (4).
Certain medicines: taking statins is a known drug-induced cause of myalgia, sometimes accompanied by diffuse pain, stiffness or exercise intolerance.
Fibromyalgia: this syndrome of chronic widespread pain associated with central sensitisation, often accompanied by fatigue and sleep disturbances, is underpinned by complex neurophysiological mechanisms (4).
Joint pain
Joint injury: a sprain, ligament injury, fracture or repeated microtrauma can cause secondary mechanical or inflammatory pain.
Osteoarthritis: the most common cause of joint pain is linked to the gradual breakdown of cartilage and changes in the subchondral bone (the layer of bone beneath the cartilage). The pain is often mechanical in nature, worsening with exertion, and accompanied by brief stiffness upon waking.
Inflammatory arthritis: rheumatoid arthritis, psoriatic arthritis and spondyloarthritis result in painful, stiff and sometimes swollen joints, with a more pronounced inflammatory component at night and in the morning (2).
Gout: Gout and other microcrystalline arthropathies cause crystals to be deposited in the joint, triggering acute inflammation that is often very severe, with redness, a sensation of heat and swelling, sometimes affecting a single joint.
Joint infection: septic arthritis generally presents with severe pain, a warm, swollen joint and a deterioration in general health, and can rapidly damage the cartilage.
Certain systemic or autoimmune diseases: lupus, coeliac disease, sarcoidosis, myositis and other inflammatory conditions can cause joint pain or secondary arthritis, often accompanied by rashes, dryness, digestive problems or persistent fatigue (2).
Mixed pain
Fibromyalgia, viral infections, systemic inflammatory diseases and certain adverse drug reactions can cause both muscle and joint pain. The distribution of pain, the presence of joint swelling, morning stiffness and general symptoms should be considered in order to pinpoint the location of the pain and identify its cause. Mechanical pain tends to worsen with use, while inflammatory pain is more pronounced at rest, at night or upon waking (2, 4).
