Purpose: To document the recovery of knee function following Medial Collateral Ligament (MCL) injury of the knee.

Methods and Results A cohort of 38 consecutive patients with MCL injuries were followed prospectively from the time of injury for a period of one year. There were 13 grade I MCL sprains and 25 grade II sprains. Twelve patients had a concomitant ACL tear. Patients were treated in a hinged knee brace with full extension and 90 degrees of knee flexion for 6 weeks from the date of injury. All patients had an identical rehabilitation programme. Clinical outcome was assessed using two standard functional knee scores (International Knee Documentation Committee (IKDC) score and Knee Outcome Orthopaedic Score (KOOS)). Quadriceps and hamstring muscle function was tested isokinetically using a dynamometer. Outcome assessments were carried out at 2 weeks, 6 weeks, 3 months, 6 months and 1 year.

At 2 weeks the average range of motion (ROM) difference from the normal side was 31%. Twenty-five patients (66%) restored a functional range of motion (5–120 degrees) by 6 weeks. Thirty-five patients (92%) had a normal ROM by 3 months. Peak torque, average power and total work of quadriceps and hamstring muscle groups were normal in 4 patients (11%) at 6 weeks. At 3 months 11 patients (29%) had restored normal muscle function. At 6 months 46% of patients had normal muscle function. At 1 year 11 patients (29%) still had abnormalities of muscle function on isokinetic testing.

Conclusions: Patients with MCL injuries can be advised that range of motion can be expected to return to normal in the majority of cases by 3 months but muscle function recovers more slowly over 12 months following injury.