Pain in the leg is a vague description. If the pain is in and around the knee, it could be due to something inside the knee. If the pain is in the muscle part which is the calf or other muscles, the pain could be either electrolyte imbalance which causes spasms in the muscles which is quite common in summer. It could also we due to a spine related issues which cause radiating pain. Try starting physiotherapy. Even if you're diagnosed with early arthritis or any other condition which is common in this age group, strengthening exercises cause relief if done atleast for 2-3 weeks.
Next Steps
Orthopaedic consultation is required to come to a diagnosis
Health Tips
Plain radiographs (X-rays) of the concerned part where there is pain. X-rays AP and Lateral of the concerned part