Background: Glenohumeral internal rotation deficit (GIRD) is shared physical deficiency found in teenagers and overhead many sports. GIRD is usually categorized as simultaneous internal rotation deficits (IR).

Objective: The study's objective was to compare the effects of Mulligan internal rotation Mobilization and post isometric relaxation technique on Pain, Range of motion and function in patients.

Methods: A randomized clinical trial was conducted in the Physiotherapy department of A.R hospital Lahore. A convenient sample of 24 diagnosed patients with GIRD were randomly distributed into two groups with the use of the lottery method. Group A patients got Mulligan internal rotation mobilization treatment and Group B got Post Isometric relaxation (PIR) treatment. The goniometry, Numeric pain rating scale (NPRS), Shoulder range of motion (ROM), and The Shoulder Pain and Disability Index (SPADI were used to assess all patients before and after two weeks of intervention. Statistical analysis was computed by SPSS 25.0.

Results: There is a statistically significant difference between group analysis. Pain decreased to a greater extent in post-treatment of Mulligan internal rotation MWM group with mean value 2.50±1.88 as compared to 4.42±1.16 of Post isometric relaxation group. SPADI Score showed a greater extent in posttreatment of Mulligan Internal rotation MWM with mean value 50.08 ±8.02 as compared to Post isometric relaxation group 60.00± 13.67. Mulligan Internal rotation MWM group showed greater improvement in Range with a mean value of 68.92±11.97 as compared to Post isometric relaxation group with a mean value of 54.92±8.45.

Conclusion: The study concludes that Mulligan internal rotation Mobilization was more effective than post isometric Relaxation for pain, function, and internal rotation range of motion in patients with Glenohumeral internal rotation deficit.

Index Terms- Pain, function, movement, Mobilization with movement, post-isometric relaxation)