The muscular components of the lower leg include the gastrocnemius, soleus, peroneus longus, tibialis anterior, extensor digitorum longus, and the achilles tendon.

Leg pain in older children or young adolescents can occur for many reasons. An Osgood-Schlatter lesion results from continued trauma to the anterior tibial bone and causes a visible lump below the knee.

The location of knee pain can help identify the problem. Pain on the front of the knee can be due to bursitis, arthritis, or softening of the patella cartilage as in chondromalacia patella. Pain on the sides of the knee is commonly related to injuries to the collateral ligaments, arthritis, or tears to the meniscuses. Pain in the back of the knee can be caused by arthritis or cysts, known as Baker's cysts. Baker's cysts are an accumulation of joint fluid (synovial fluid) that forms behind the knee. Overall knee pain can be due to bursitis, arthritis, tears in the ligaments, osteoarthritis of the joint, or infection.

Instability, or giving way, is also another common knee problem. Instability is usually associated with damage or problems with the meniscuses, collateral ligaments, or patella tracking.

A baker's cyst is seen as a swelling behind the knee. It forms when joint fluid collects behind the knee. The swelling may be due from inflammation or from other causes, like arthritis. The condition can be seen in both adults and children.

Tendinitis is inflammation, irritation, and swelling of a tendon, which is the fibrous structure that joins muscle to bone. Tendinitis pain in the knee is located in the front of the knee. The pain gets worse when going up and down stairs or inclines. Tendinitis knee pain can happen in runners, skiers, and cyclists.