laid down in bed for two days; left knee swelled up last week; he can barely run 2 blocks now; diagnosed with pseudogout in the left knee; inflammation problems in the left knee and right elbow.; experienced pain all over the knee; This spontaneous case was reported by a consumer and describes the occurrence of MOBILITY DECREASED (laid down in bed for two days), JOINT SWELLING (left knee swelled up last week), GAIT DISTURBANCE (he can barely run 2 blocks now), CHONDROCALCINOSIS PYROPHOSPHATE (diagnosed with pseudogout in the left knee) and ARTHRITIS (inflammation problems in the left knee and right elbow.) in a 61-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     The patient's past medical history included Back surgery, Neck surgery, Surgery (Hand surgery), Wrist surgery, Surgery (right toe surgery), Surgery (ankles surgery), Surgery (left thumb surgery) and Knee surgery NOS (left knee surgery for torn meniscus) in November 2020. Concurrent medical conditions included Chronic pain and Hypothyroidism (low thyroid level). Concomitant products included LEVOTHYROXINE SODIUM (SYNTHROID) for Hypothyroidism, PARACETAMOL (TYLENOL [PARACETAMOL]) and IBUPROFEN for an unknown indication.   On 01-Mar-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 01-Apr-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) dosage was changed to 1 dosage form. On 01-Apr-2021, the patient experienced MOBILITY DECREASED (laid down in bed for two days). In April 2021, the patient experienced JOINT SWELLING (left knee swelled up last week), GAIT DISTURBANCE (he can barely run 2 blocks now), CHONDROCALCINOSIS PYROPHOSPHATE (diagnosed with pseudogout in the left knee), ARTHRITIS (inflammation problems in the left knee and right elbow.) and ARTHRALGIA (experienced pain all over the knee). The patient was treated with MAGNESIUM for Adverse event, at an unspecified dose and frequency; CORTISONE for Adverse event, at an unspecified dose and frequency and COLCHICINE for Adverse event, at an unspecified dose and frequency. On 03-Apr-2021, MOBILITY DECREASED (laid down in bed for two days) had resolved. At the time of the report, JOINT SWELLING (left knee swelled up last week), GAIT DISTURBANCE (he can barely run 2 blocks now), CHONDROCALCINOSIS PYROPHOSPHATE (diagnosed with pseudogout in the left knee) and ARTHRALGIA (experienced pain all over the knee) outcome was unknown and ARTHRITIS (inflammation problems in the left knee and right elbow.) had not resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In April 2021, Chondrocalcinosis pyrophosphate: abnormal (abnormal) The doctor drained his left knee which contained calcium crystals..         other treatment information included he was directed to drink a lot of water.  The caller mentioned he has no past history of high blood calcium in the blood.  This case concerns a 61-year-old, male patient with medical history of left knee surgery (November 2020), 15 surgeries including the back, neck, hands, wrists, right toe, ankles, and left thumb, chronic pain all over his body from the past surgeries, who experienced the non-serious unexpected events of special interest of arthritis, non-serious expected event of arthralgia, non-serious unexpected events of mobility decreased, joint swelling, gait disturbance, chondrocalcinosis pyrophosphate. The event mobility decreased occurred the same day after the second dose of Moderna COVID-19 vaccine. The events arthritis, arthralgia, joint swelling, gait disturbance, chondrocalcinosis pyrophosphate occurred on the same month after the second dose of Moderna COVID-19 vaccine.  The rechallenge was assessed as not applicable as the AEs occurred after the second dose. Patient's medical history of 15 surgeries including the back, neck, hands, wrists, right toe, ankles, and left thumb, chronic pain all over his body from the past surgeries remain confounders. The benefit-risk relationship of Moderna COVID-19 vaccine is not affected by this report.  He reported that recently his Synthroid dose was reduced.; Sender's Comments: This case concerns a 61-year-old, male patient with medical history of left knee surgery (November 2020), 15 surgeries including the back, neck, hands, wrists, right toe, ankles, and left thumb, chronic pain all over his body from the past surgeries, who experienced the non-serious unexpected events of special interest of arthritis, non-serious expected event of arthralgia, non-serious unexpected events of mobility decreased, joint swelling, gait disturbance, chondrocalcinosis pyrophosphate. The event mobility decreased occurred the same day after the second dose of Moderna COVID-19 vaccine. The events arthritis, arthralgia, joint swelling, gait disturbance, chondrocalcinosis pyrophosphate occurred on the same month after the second dose of Moderna COVID-19 vaccine.  The rechallenge was assessed as not applicable as the AEs occurred after the second dose. Patient's medical history of 15 surgeries including the back, neck, hands, wrists, right toe, ankles, and left thumb, chronic pain all over his body from the past surgeries remain confounders. The benefit-risk relationship of Moderna COVID-19 vaccine is not affected by this report.