Ligamentous sprain: knee ligaments have stretched more than normal or torn, but are not permanently damaged

  • Symptoms: pain around the knee, swelling, bruising, unable to put weight on the knee, tenderness
  • Causes: sudden increase in activity level, abrupt change in direction or speed, landing awkwardly, collisions with an object or other person

Torn meniscus: damage to the rubbery pads between the upper and lower leg bones, often occur along with damage to knee ligaments (see ligamentous sprains)

  • Symptoms: deep pain in the knee, swelling, knee locks up unexpectedly, a popping sensation during the injury, difficulty bending and straightening the leg
  • Causes: changing direction suddenly, repeated squatting or stepping, general aging

Osteoarthritis: joint cartilage and the underlying bone begin to degrade

  • Symptoms: pain and stiffness in the knees, tenderness, grating or cracking feeling, limited motion
  • Causes: aging, family history

Popliteal cyst (Baker’s cyst): a fluid-filled swelling forms on the back of the knee

  • Symptoms: lump or fluid on the back of the knee, pain in the knee and calf, occasional locking or clicking in the knee
  • Causes: any knee injury, including a blow to the knee, osteoarthritis, rheumatoid arthritis, or gout

Patellar tendinitis: the tendon that connect the kneecap to the joint become inflamed

  • Symptoms:  pain and tenderness in the front of the knee, swelling, redness
  • Causes: overuse of the knee, such as repeated jumping or kneeling, can develop into tendinopathy

Bursitis: inflammation of the bursa, a fluid-filled sac that lies between bones to act as a cushion

  • Symptoms: pain around the knee that increases with movement or pressure, tenderness, swelling, loss of movement
  • Causes: repetitive movements like long distance running, hard blow to the knee, overuse of the knee

Patellofemoral pain (runner or jumper’s knee): pain in the front part of the knee, specifically around the knee cap

  • Symptoms: dull, aching pain in the front of the knee that begins gradually and is worse when bending the knee or after long periods of sitting, popping or crackling sounds
  • Causes: changes in activity intensity or duration, patellar malalignment

Patellar maltracking: the patella (knee cap) is pulled in a certain direction and rubs against the femu

  • Symptoms: visible shifting of the patella to one side, knee locks and cannot be unlocked, pain around the patella
  • Causes: strength imbalance in the quadriceps muscles, flat patella, patella that sits high on the femur 

Osgood-Schlatter disease: the bone, cartilage, or tendon at the top of the shinbone becomes inflame

  • Symptoms: pain in the knee that worsens with exercise and gets better with rest, swelling, tenderness, intermittent pain over several months, bony bump develops in some cases
  • Causes: overuse of the quadriceps muscle in adolescence

Hypermobility (double-jointed): knee joint has an unusually large range of motion

  • Symptoms: stiffness in the knee, clicking noise when moving, dislocation of the knee, recurrent injuries such as sprains
  • Causes: family history, overstretching of the joint such as in gymnastics or ballet

Gout: uric acid buildup in the blood results in crystals forming in and around joints

  • Symptoms: sudden severe pain in the knee, swelling, redness, pain lasting 3 to 10 days after onset
  • Causes: diuretics, alcohol, family history, hypothyroidism, obesity, kidney problems