Depending on the cause, pain on the inside of the knee arises after an injury or gradually appears. Some individuals, such as those who have knock-knees, are more likely to develop medial knee pain. Understanding the source of medial knee pain allows appropriate treatment to be initiated and preventive measures to be taken to avoid further pain.
Medial Knee Structures
Most of the body's weight is transmitted through the medial side of the knee. The medial meniscus, acting as a cushion, sits between the thighbone or femur and the tibia. Connecting the femur and tibia is the joint capsule and the two layer medial collateral ligament. The medial collateral bursa is between superficial and deep layers of the medial collateral ligament.
The knee is extended by the quadriceps muscles. It connects to the patella, or kneecap, on the front of the knee. The knee is flexed by the quadriceps muscles. One of the quadriceps muscles, the semimembranosus muscle attaches on the posterior medial tibia at the knee. The pes anserine is the site where three muscles attach on the anterior medial tibia at the knee.
All of the medial joint structures can be the source of pain.
Meniscus
Meniscus injuries are one of the common sources of medial knee pain. The medial meniscus is larger than the lateral meniscus and is more commonly injured. Tears can occur from twisting injuries. With age, water is lost from the menisci making it more vulnerable to tears. With normal activity degenerative tears can occur. On exam there is medial joint line tenderness. After a meniscal tear, fluid can accumulate creating a painful cyst. Usually meniscal cysts are small and not palpable, but they can be 8 cm or larger and easily felt by the patient. Arthroscopic surgery may be recommended.
Medial Collateral Ligament
The medial collateral ligament can be partially torn by valgus force, which is from the lateral side of the knee. The MCL is injured in football players during cutting or tackling. The knee may be unstable and is painful over the MCL. The treatment is initially rest and ice. Bracing and physical therapy are then started.
The medial collateral bursa can become inflamed producing pain in the area of the MCL. A nodule anterior to the MCL may be palpated in some patients. Patients who have arthritis or put pressure on the inside of their knee by horseback riding are more likely to develop MCL bursitis. Treatment is by ice, non-steroidal anti-inflammatory medication and avoiding activity that irritates it.
Patella
The kneecap is anchored by several medial structures. The patella dislocates laterally tearing the anterior medial anchoring ligaments. Patella mal-alignment pain is typically anterior and medial. Inside the joint there may be a thickening of the joint capsule, suprapatella plica, which causes pain. These conditions are more common in teenage females and those with lax joints.
Hamstring Insertion Bursa
At the insertion of the hamstring tendons there are bursa which can become inflammed. The pes anserine bursa is on the anterior tibia and the semimembranosus bursa is posterior medial. Rest, ice and non-steroid anti-inflammatory medication is the initial treatment. Stretching of tight hamstring muscles is recommended by the University of Minnesota Sports Medicine Institute.
Inflammation of the infrapatellar branch of the saphenous nerve also produces tenderness near the pes anserine bursa.
Bone
Degenerative arthritis, osteoarthritis, is a common cause of medial knee pain. Other arthritic conditions such as gout and rheumatoid arthritis can affect the knee. People with unequal leg length or valgus knees are more prone to arthritis. Excess weight causes increased knee joint wear and early arthritis.
Several different types of fractures occur around the knee joint. In patients with weak bones, osteoporosis, the fracture may happen with a minor fall.
Infection
Infection can occur inside or outside the joint. Superficial infection causes a red, tender area. The first symptom of septic arthritis or infection inside the joint may be pain. The knee joint becomes swollen and warm. Medical attention should be promptly sought. The treatment for infection inside the joint is surgery and prolonged antibiotics.
References
- MR Imaging of Meniscal Cysts: Incidence, Location, and Clinical Significance; Scot E. Campbell, Timothy G. Sanders and William B. Morrison; 2001
- MR Imaging of the Medial Collateral Ligament Bursa; Findings in Patients and Anatomic Data Derived from Cadavers; Michel De Maeseneer1, Maryam Shahabpour, Frans Van Roy, Anita Goossens, Filip De Ridder, Jan Clarijs and Michel Osteaux; 2001
- University of Minnesota Orthopaedics: Sports Medicine Institute: Knee Tenderness and Pain
- Mayo Clinic: Knee Pain: Symptoms
- American Academy of Orthopaedic Surgeons; Save Your Knees
