Overview
what it is and why it mattersThe ulnar collateral ligament (UCL) is the main ligament on the inner side of your elbow. Its job is to stop your elbow from bending sideways toward your body when load is applied. That sounds simple, but during the cocking phase of a baseball pitch, the inner elbow takes one of the highest forces measured in any sport — and the UCL is what keeps it together. UCL injuries run from minor sprains (grade I-II) all the way to a complete tear (grade III). It's the defining injury of baseball pitchers, but javelin throwers, quarterbacks, and wrestlers see it too.
Diagnosis
exam first, imaging secondPain on the inner side of the elbow when throwing, plus a noticeable drop in velocity, and instability when your provider applies sideways stress to a slightly bent elbow. The most sensitive exam test is the moving valgus stress test — moving the bent elbow through its arc while applying a gentle inward stress reproduces the pain. An MRI with contrast injected into the joint (MRI arthrography) shows partial or complete UCL tears. Nerve-conduction studies are added when we want to rule out a pinched nerve as a cause — either carpal tunnel at the wrist or cubital tunnel at the elbow.
Treatment Path
how care progresses at OSI1
Rest and activity modification
For grade I-II sprains, the first move is a complete throwing break for several weeks — no exceptions. Once the pain has settled, return to throwing follows a structured interval program: short toss before long toss, flat ground before mound work, building gradually.
2
Physical therapy
PT focuses on three pieces: strengthening the forearm muscles that share the load with the UCL, stretching the back of the shoulder (which gets tight in throwers and shifts stress onto the elbow), and cleaning up throwing mechanics so the same forces don't keep loading the same ligament.
3
PRP injection
An injection of platelet-rich plasma (PRP) — concentrated growth factors drawn from your own blood — placed precisely at the partial UCL tear has growing evidence in this exact scenario. For a subset of pitchers with partial tears, PRP plus structured rehab gets them back to throwing without surgery.
Surgical Options at OSI
if non-operative care isn't enoughFor competitive throwers with a complete UCL tear, or partial tears that haven't responded to rehab and PRP, the answer is UCL reconstruction — popularly known as Tommy John surgery. The torn ligament is rebuilt with a tendon graft (often from the patient's own forearm or hamstring) and woven through small bone tunnels at the elbow.
Providers Who Treat Ucl Injury
sports-medicine team
Further Reading
authoritative sourcesExternal patient-education references and related OSI pages for additional background: